Keyword: laser
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MOZGBD1 Towards Full Performance Operation of SwissFEL FEL, experiment, photon, electron 24
 
  • T. Schietinger
    PSI, Villigen PSI, Switzerland
 
  SwissFEL is the new X-ray free-electron laser facility at the Paul Scherrer Institute (PSI) in Switzerland. It was inaugurated in December 2016 and saw its first pilot experiments at the end of 2017. We describe the commissioning steps leading to the first phase of pilot experiments and outline the plans towards reaching nominal performance levels in 2018.  
slides icon Slides MOZGBD1 [11.395 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBD1  
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MOZGBD5 A Proposal for Coherent Hard X-Ray Generation Based on Two-Stage EEHG FEL, electron, linac, radiation 38
 
  • Z.T. Zhao, J.H. Chen, C. Feng, Z. Wang, K.Q. Zhang
    SINAP, Shanghai, People's Republic of China
 
  A two stage echo-enabled harmonic generation (EEHG) scheme to produce coherent hard X-rays is presented. Electron bunchs of quite different lengths are separately used in each stage of EEHG and a monochromator is employed to purify the radiation from the first stage for seeding the second one. Theoretical analysis and 3D simulations show that the proposed scheme can generate fully coherent hard X-ray pulses directly from a conventional UV seed laser.  
slides icon Slides MOZGBD5 [7.335 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBD5  
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MOPMF029 FCC-hh transverse impedance budget impedance, injection, feedback, electron 149
 
  • S. Arsenyev, D. Schulte
    CERN, Geneva, Switzerland
  • O. Boine-Frankenheim
    GSI, Darmstadt, Germany
 
  Contributions of different machine elements of the proposed Future Circular Collider (FCC-hh) impedance budget are calculated based on beam stability considerations. For each element (the beamscreen, the collimators, etc), effective impedances are calculated at the injection energy and at the collision energy for considered instabilities. The considered instabilities include the transverse coupled bunch instability (TCBI) and the transverse mode coupling instability (TMCI). Limitations to each total effective impedance are estimated and the critical points in the impedance budget are determined.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF029  
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MOPMF031 Modelling Wake Impedance of a Rough Surface in Application to the FCC-hh Beamscreen impedance, coupling, electron, vacuum 157
 
  • S. Arsenyev, D. Schulte
    CERN, Geneva, Switzerland
 
  The inner surface of the future circular collider (FCC-hh) beamscreen is proposed to be laser-treated in order to mitigate the electron cloud build-up. However, the rough structure of the treated surface can result in unwanted impedance increase, potentially leading to the transverse mode coupling instability (TMCI). Three models have been adopted to estimate the wake impedance of a beamscreen with a rough surface. The models use the resistive wall formalism generalized for the case of an arbitrary surface impedance. The results apply to a beamscreen of a circular cross-section with the homogeneously rough inner surface for the case of ultrarelativistic particles. The free parameters of the models were fit into preliminary measurements of the surface resistivity, giving, as a result, a range of the real and the imaginary parts of the wake impedance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF031  
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MOPML030 Demonstration of a Tunable Electron Beam Chopper for Application in 200 kV stroboscopic TEM electron, kicker, experiment, controls 467
 
  • C.-J. Jing, S.V. Baryshev, A. Kanareykin, A. Liu, Y. Zhao
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • J.W. Lau
    NIST, Gaithersburg, Maryland, USA
  • D. Masiel, B. Reed
    Integrated Dynamic Electron Solutions, Pleasanton, California, USA
  • Y. Zhu
    BNL, Upton, Long Island, New York, USA
 
  Funding: The project is supported by the Office of Basic Energy Science of DOE through a Small Business Innovative Research grant #DE-SC0013121.
For the last several decades, time-resolved transmission electron microscopes (TEM) exploring the sub-microsecond timescale have relied on the photoemission technology to generate the single or train of electron bunches. However, the complexity of additional laser system and the availability of high repitition rate laser limit applications of the laser-driven approach. Lately we have made substantial progress towards pioneering a new kind of time-resolved TEM, complementary to the existing laser-based techniques. Using a tunable RF beam-chopper, we are able to retrofit an exsiting TEM providing a pulsed electron beam at a continuously tunable reptition rate up to 12GHz and a tunable bunch length. In the article we will briefly discuss the working principle and experimental progress to date.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML030  
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MOPML031 Highlights of Accelerator Activities in France on Behalf of the Accelerator Division of the French Physics Society linac, proton, operation, electron 470
 
  • J.-L. Revol
    ESRF, Grenoble, France
  • S. Chel
    CEA/IRFU, Gif-sur-Yvette, France
  • B. Cros
    CNRS LPGP Univ Paris Sud, Orsay, France
  • N. Delerue
    LAL, Orsay, France
  • E. Giguet
    ALSYOM, Versailles, France
  • V. Le Flanchec
    CEA/DAM, Bruyères-le-Châtel, France
  • L.S. Nadolski
    SOLEIL, Gif-sur-Yvette, France
  • L. Perrot
    IPN, Orsay, France
  • A. Savalle
    GANIL, Caen, France
  • T. Thuillier
    LPSC, Grenoble Cedex, France
 
  The French Physical Society is a non-profit organization working to advance and diffuse the knowledge of physics. Its Accelerators division contributes to the promotion of accelerator activities in France. This paper presents the missions and actions of the division, high-lighting those concerning young scientists. A brief presentation of the laboratories, institutes, and facilities that are the main actors in the field is given. Significant ongoing and planned projects in France are described, including medical applications. Main French contributions in inter-national projects are then listed. Finally, cultural and technical relationships between industry and laboratories are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML031  
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MOPML044 Start-to-End Beam Dynamic Simulations for PRAE gun, emittance, linac, solenoid 495
 
  • A. Vnuchenko
    IFIC, Valencia, Spain
  • C. Bruni, M. El Khaldi, A. Faus-Golfe, P. Lepercq, C. Vallerand
    LAL, Orsay, France
  • A. Latina
    CERN, Geneva, Switzerland
 
  The PRAE project (Platform for Research and Applications with Electrons) aims at creating a multidisciplinary R&D facility in the Orsay campus gathering various scientific communities involved in radiobiology, subatomic physics, instrumentation and particle accelerators around an electron accelerator delivering a high-performance beam with energy up to 70 MeV and later 140 MeV, in order to perform a series of unique measurements and future challenging R&D. In this paper we report the first start-to-end simulations from the RF gun, going through the linac and finally to the different experimental platforms. The beam dynamics simulations have been performed using a concatenation of codes. In particular for the linac the RF-Track code recently developed at CERN will be used and benchmarked. The different working points have been analysed in order to minimise the transverse emittance and the beam energy spread including space charge effects at low electron energies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML044  
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MOPML049 Generation of 1-MeV Quasi-Monochromatic Gamma-Rays for Precise Measurement of Delbrück Scattering by Laser Compton Scattering scattering, electron, experiment, photon 508
 
  • H. Zen, T. Kii, H. Ohgaki
    Kyoto University, Kyoto, Japan
  • M. Fujimoto, M. Katoh, E. Salehi
    UVSOR, Okazaki, Japan
  • T. Hayakawa, T. Shizuma
    QST, Tokai, Japan
  • M. Katoh
    Sokendai - Okazaki, Okazaki, Aichi, Japan
  • J. Koga
    National Institutes for Quantum and Radiological Science and Technology, Kyoto, Japan
  • E. Salehi
    AUT, Tehran, Iran
 
  Delbrück scattering is the elastic scattering of photons by the electromagnetic field of an atomic nucleus, as a consequence of vacuum polarization. The isolated measurement of Delbrück scattering has not been performed because of interference with other elastic scattering processes. It was recently discovered that, using linearly polarized photons, Delbrück scattering can be measured nearly independently of the other scattering processes*. In order to perform a proof of principle experiment, a quasi-monochromatic gamma-ray beam with a maximum photon energy of 1 MeV has been generated at the UVSOR facility by colliding a CO2 laser with a 750-MeV electron beam. A preliminary experiment has been performed with 0.5-W laser power and 1-mA electron beam current. As a result, the measured gamma-ray flux was evaluated as 0.0006 photon/eV/mA/W/s around the peak energy of 1 MeV. If we accept 20 percent energy spread, in case of a 100-W CO2 laser colliding with a 300 mA electron beam, approximately 4 x 106-photons/s gamma-rays could be obtained. This flux is sufficiently high for the proof of principle experiment.
*J.K. Koga and T. Hayakawa, Phys. Rev. Lett. 118, 204801 (2017).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML049  
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MOPML066 Ultrafast Mega-electron-volt Gas-Phase Electron Diffraction at SLAC National Accelerator Laboratory electron, gun, vacuum, experiment 556
 
  • X. Shen, R.K. Li, X.J. Wang, S.P. Weathersby, J. Yang
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported in part by the U.S. Department of Energy Contract No. DE-AC02-76SF00515, and the SLAC UED/UEM Initiative Program Development Fund.
Ultrashort mega-electron-volt (MeV) electron beams from radio-frequency (rf) photoinjectors have recently attracted strong interests for application in ultrafast gas-phase electron diffraction (UGED). Such high-brightness electron beams are capable of providing 100-fs level temporal resolution and sub-Angstrom level spatial resolution to capture the ultrafast structural dynamics from photoexcited gas molecules. To experimentally demonstrate such an ultrafast electron scattering instrument, a high performance UGED system has been commissioned at SLAC National Accelerator Laboratory. The UGED instrument produces 3.7 MeV electron beams with 2 fC beam charge at 180-Hz repetition rate. The temporal resolution is characterized to be 150 fs full-width-at-half-maximum (FWHM), while the spatial resolution is measured to be 0.76 Å FWHM. The UGED instrument also demonstrates outstanding performance in vacuum, rf, and electron beam pointing stability. Details of the performance of the SLAC MeV UGED system is reported in this paper.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML066  
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MOPML068 Training the Next Generation of Accelerator Experts network, FEL, electron, synchrotron 564
 
  • C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Funding: Work supported by the European Union under grant agreements no 215080, 289191, 289485, 675265 and 721559.
Close collaboration between academia, research centres and industry has turned out to be crucial for the advancement of accelerator science and technology. It is also ideal for providing an efficient training of the next generation of particle accelerator experts and for linking the global accelerator community. Five international research and training networks (DITANET, oPAC, LA3NET, OMA and AVA) have been initiated and coordinated by the University of Liverpool/Cockcroft Institute since 2007. These networks have provided training to almost 100 Fellows from all over the world and organised dozens of international schools, topical workshops and international conferences for the accelerator community. The research activities of the networks have led to hundreds of journal publications and conference proceedings. This contribution presents the best practice in establishing such international collaborative projects, how to establish successful links between sectors and countries, and highlights the main research results that resulted from the research programs.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML068  
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TUXGBD1 Potential and Issues for Future Accelerators and Ultimate Colliders emittance, controls, photon, synchrotron 578
 
  • S.J. Brooks
    BNL, Upton, Long Island, New York, USA
 
  Particle colliders have been remarkably successful tools in particle and nuclear physics. What are the future trends and limitations of accelerators as they currently exist, and are there possible alternative approaches? What would the ultimate collider look like? This talk examines some challenges and possible solutions. Accelerating a single particle rather than a thermal distribution may allow exploration of more controlled interactions without background. Also, cost drivers are possibly the most important limiting factor for large accelerators in the foreseeable future so emerging technologies to reduce cost are highlighted.  
slides icon Slides TUXGBD1 [2.590 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBD1  
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TUXGBE4 Beam Quality Limitations of Plasma-Based Accelerators plasma, electron, injection, acceleration 607
 
  • A. Ferran Pousa, R.W. Aßmann
    DESY, Hamburg, Germany
  • A. Martinez de la Ossa
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Plasma-based accelerators are a promising novel technology that could significantly reduce the size and cost of future accelerator facilities. However, the typical quality and stability of the produced beams is still inferior to the requirements of Free Electron Lasers (FELs) and other applications. We present here our recent work in understanding the limitations of this type of accelerators, particularly on the energy spread and bunch length, and possible mitigating measures for future applications, like the plasma-based FEL in the EuPRAXIA design study.  
slides icon Slides TUXGBE4 [4.910 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBE4  
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TUPAF006 Operation of RHIC Injectors with Isobaric Ruthenium and Zirconium Ions target, booster, ion-source, injection 672
 
  • H. Huang, E.N. Beebe, I. Blacker, J.J. Butler, C. Carlson, P.S. Dyer, W. Fischer, C.J. Gardner, D.M. Gassner, D. Goldberg, T. Hayes, S. Ikeda, J.P. Jamilkowski, T. Kanesue, N.A. Kling, C. Liu, D. Maffei, G.J. Marr, B. Martin, J. Morris, C. Naylor, M. Okamura, D. Raparia, V. Schoefer, F. Severino, T.C. Shrey, K.S. Smith, D. Steski, P. Thieberger, K. Zeno, I.Y. Zhang
    BNL, Upton, Long Island, New York, USA
  • H. Haba
    RIKEN Nishina Center, Wako, Japan
  • T. Karino
    Utsunomiya University, Utsunomiya, Japan
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The FY18 RHIC physics program calls for Ru-Ru and Zr-Zr collisions at 100GeV using isobaric Ruthenium and Zirconium ions, each having 96 nucleons. In the injector chain, these two ions have to come from tandem and EBIS source, respectively. To reduce systematic errors in the detector, the luminosity between the two species combinations is matched as closely as possible, and the species are switched frequently. Several bunch merges are needed in the Booster and AGS to reach the desired bunch intensity for RHIC. The setup and performance of Booster and AGS with these ions are reviewed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF006  
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TUPAK007 Simulation of Surface Muon Beamline, Ultra-Slow Muon Production and Extraction for the J-PARC g-2/EDM Experiment simulation, target, experiment, proton 970
 
  • M. Otani, N. Kawamura, T. Mibe, T. Yamazaki
    KEK, Tsukuba, Japan
  • K. Ishida
    RIKEN Nishina Center, Wako, Japan
  • G. Marshall
    TRIUMF, Vancouver, Canada
 
  The E34 experiment aims to measure muon anomalous magnetic moment with a precision of 0.1 ppm to cast light on beyond standard model in elementary particle physics. The experiment utilizes a brand new muon beam line in J-PARC (H line), which is designed to have large acceptance to supply an intense muon beam. The surface muons are injected into a silica aerogel target to generate bound state of muon and electron (muonium). Then the muoniums are ionized by lasers and ultra slow (30 meV) muons (USM) are generated. The USM's are extracted by electro-static lens and injected to a muon linac. In this poster, simulation for optics of the surface muon beamline, muonium production and extraction by the electro-static lens, and the estimation of the USM's intensity are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK007  
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TUPAL045 Towards Operational Scalability for H Laser Assisted Charge Exchange experiment, cavity, operation, radiation 1110
 
  • S.M. Cousineau, A.V. Aleksandrov, T.V. Gorlov, Y. Liu, M.A. Plum, A. Rakhman, A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  • D.E. Johnson, S. Nagaitsev
    Fermilab, Batavia, Illinois, USA
  • M.J. Kay
    UTK, Knoxville, Tennessee, USA
 
  The experimental development of H laser assisted charge exchange, a.k.a. laser stripping, has been ongoing at the SNS accelerator since 2006 in a three-phase approach. The first two phases associated with proof-of-principle and proof-of-practicality experiments have been successfully completed and demonstrated >95% H stripping efficiency for up to 10 us. The final phase is a proof-of-scalability stage to demonstrate that the method can be deployed for realistic beam duty factors. The experimental component of this effort is centered on achieving high efficiency stripping through the use of a laser power amplification scheme to recycle the macropulse laser light at the interaction point of the H stripping. Such a recycling cavity will be necessary for any future operational laser stripping system with at least millisecond duration H pulses. A second component of the proof-of-scalability phase is to develop a conceptual design for a realistic laser stripping scheme. The status of these efforts and challenges associated with deploying the recycling cavity into the laser stripping experiment will be described in this talk.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL045  
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TUZGBE3 Towards Implementation of Laser Engineered Surface Structures for Electron Cloud Mitigation electron, vacuum, operation, multipactoring 1220
 
  • M. Sitko, V. Baglin, S. Calatroni, P. Chiggiato, B. Di Girolamo, E. Garcia-Tabares Valdivieso, M. Taborelli
    CERN, Geneva, Switzerland
  • A. Abdolvand, D. Bajek, S. Wackerow
    University of Dundee, Nethergate, Dundee, Scotland, United Kingdom
  • M. Colling, T.J. Jones, P.A. McIntosh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  The LHC operation has proven that the electron cloud could be a significant limiting factor in machine performance, in particular for future High Luminosity LHC (HL-LHC) beams. Electron clouds, generated by electron multipacting in the beam pipes, leads to beam instabilities and beam-induced heat load in cryogenic systems. Laser Engineered Surface Structures (LESS) is a novel surface treatment which changes the morphology of the internal surfaces of vacuum chambers. The surface modification results in a reduced secondary electron yield (SEY) and, consequently, in the eradication of the electron multipacting. Low SEY values of the treated surfaces and flexibility in choosing the laser parameters make LESS a promising treatment for future accelerators. LESS can be applied both in new and existing accelerators owing to the possibility of automated in-situ treatment. This approach has been developed and optimised for the LHC beam screens in which the electron cloud has to be mitigated before the HL-LHC upgrade. We will present the latest steps towards the implementation of LESS.  
slides icon Slides TUZGBE3 [1.830 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBE3  
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TUPMF002 A Cu Photocathode for the Superconducting RF Photoinjector of BERLinPro cathode, gun, SRF, cavity 1247
 
  • J. Kühn, M. Bürger, A. Frahm, A. Jankowiak, T. Kamps, G. Klemz, G. Kourkafas, A. Neumann, N. Ohm, M. Schmeißer, M. Schuster, J. Völker
    HZB, Berlin, Germany
  • P. Murcek, J. Teichert
    HZDR, Dresden, Germany
 
  The initial commissioning of the Superconducting RF (SRF) photoinjector is done with a Cu photocathode due to its robustness with regard to interactions with the SRF cavity of the injector. Here we present the preparation and characterization of a Cu photocathode plug and the diagnostics to insert the photocathode in the back wall of the SRF cavity. A polycrystalline bulk Cu plug was polished, particle free cleaned and characterized by x-ray photoelectron spectroscopy. During the transfer of the photocathode insert into the gun module the whole process was controlled by several diagnostic tools monitoring the insert position as well as RF, vacuum and cryogenic signals. We discuss the challenges of the photocathode transfer into an SRF cavity and how they can be tackled.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF002  
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TUPMF005 Simulation of Inverse Compton Scattering and Its Implications on the Scattered Linewidth electron, simulation, emittance, scattering 1254
 
  • N. Ranjan, B. Terzić
    ODU, Norfolk, Virginia, USA
  • I. Drebot, L. Serafini
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  • G.A. Krafft
    JLab, Newport News, Virginia, USA
  • V. Petrillo
    Universita' degli Studi di Milano & INFN, Milano, Italy
 
  Funding: This paper is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Compton scattering, though first described some one hundred years ago, has recently experienced a surge of interest due to the search for energy sources that are capable of yielding low emission bandwidths. In particular, the desire for hard x-rays with energies greater than 10 keV has led to increased study of inverse Compton sources. The rise in interest concerning inverse Compton sources has increased the need for efficient models that properly quantify the behavior of scattered radiation given a set of interaction parameters. The current, state-of-the-art, simulations rely of Monte Carlo-based methods, which may fail to properly model collisions of bunches in low-probability regions of the spectrum. Furthermore, the random sampling of the simulations may lead to inordinately high runtimes. Our methods can properly model behaviors exhibited by the collisions by integrating over the emissions of the electrons in the bunch in a lessened amount of time. Analytical simulations of Gaussian laser beams closely verify the behavior predicted by an analytically derived scaling law describing bandwidth of scattered radiation.
Current affiliation of primary author (Nalin Ranjan) is Princess Anne High, Virginia Beach, VA 23452, USA.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF005  
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TUPMF006 Pulsed Wire Measurements of a High Field Gradient Quadrupole Wiggler quadrupole, wiggler, alignment, wakefield 1257
 
  • M. Kasa, A. Zholents
    ANL, Argonne, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
Alignment of the quadrupoles in a quadrupole wiggler to sub micrometer precision is required for the collinear wakefield accelerator that is under consideration at Argonne National Laboratory for a compact Free-Electron Laser [1]. The pulsed wire measurement method is the only technique that we are aware of that allows for sub micrometer precision and the ability to distinguish between the various quadrupoles within the wiggler. A one period prototype wiggler was manufactured and subsequently measured using the pulsed wire technique. The goal of the measurements was to verify that the magnetic centers of each quadrupole could be located and aligned to each other within the required precision. The method and results are described.
[1] A. Zholents, et al., "A preliminary design of the collinear dielectric wakefield accelerator", Nucl. Instrum. Meth. A829 (2016) 190-193.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF006  
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TUPMF020 Demonstration of Fast, Single-shot Photocathode QE Mapping Method Using MLA Pattern Beam cathode, electron, gun, optics 1293
 
  • E.E. Wisniewski, M.E. Conde, D.S. Doran, W. Gai, Q. Gao, W. Liu, J.G. Power, C. Whiteford
    ANL, Argonne, Illinois, USA
  • Q. Gao
    TUB, Beijing, People's Republic of China
  • G. Ha
    PAL, Pohang, Republic of Korea
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
 
  Funding: UChicago Argonne, LLC, Operator of Argonne National Laboratory ("Argonne"). Argonne, a U.S.A. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.
Quantum efficiency (QE) is the chief figure of merit in the characterization of photocathodes. Semiconductor photocathodes, especially when used in high rep-rate photo-injectors, are known to show QE degradation over time and must be replaced. The total QE is the basic diagnostic which is used widely and is easy to obtain. However, a QE map indicating variations of QE across the cathode surface has greater utility. It can quickly diagnose problems of QE inhomogeneity. Most QE mapping techniques require hours to complete and are thus disruptive to a user facility schedule. A fast, single-shot method has been proposed (citation) using a micro-lens array (MLA) generated QE map. In this paper we report the implementation of the method at Argonne Wakefield Accelerator facility. A micro-lens array (MLA) is used to project an array of beamlets onto the photocathode. The resulting photoelectron beam in the form of an array of electron beamlets is imaged at a YAG screen. Four synchronized measurements are made and the results used to produce a QE map of the photocathode.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF020  
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TUPMF025 LEReC Photocathode DC Gun Beam Test Results gun, cathode, operation, electron 1306
 
  • D. Kayran, Z. Altinbas, D. Bruno, M.R. Costanzo, A.V. Fedotov, D.M. Gassner, X. Gu, L.R. Hammons, P. Inacker, J.P. Jamilkowski, J. Kewisch, C.J. Liaw, C. Liu, K. Mernick, T.A. Miller, M.G. Minty, V. Ptitsyn, T. Rao, J. Sandberg, S. Seletskiy, P. Thieberger, J.E. Tuozzolo, E. Wang, Z. Zhao
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Low Energy RHIC Electron cooler (LEReC) project is presently under commissioning at Brookhaven National Laboratory (BNL). LEReC requires high average current up to 85mA and high-quality electron beam. A 400 kV DC gun equipped with a photocathode and laser system has been chosen to provide a source of high-quality electron beams. We started testing the DC gun during the RHIC run 2017. First electron beam from LEReC DC gun was delivered in April 2017 *. During the DC gun test critical elements of LEReC such as laser beam system, cathode exchange system, cathode QE lifetime, DC gun stability, beam instrumentation, the high-power beam dump system, machine protection system and controls have been tested. Average current of 10 mA for few hours of operation was reached in August 2017. In this paper we present experimental results and experience learned during the LEReC DC gun beam testing.
* D. Kayran et al., "First Results of Commissioning DC Photo-gun for RHIC Low Energy Electron Cooler (LEReC)", in Proc of ERL2017.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF025  
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TUPMF044 First Lasing of the CAEP THz FEL Facility Driven by a Superconducting Accelerator FEL, electron, free-electron-laser, undulator 1349
 
  • D. Wu, W. Bai, D.R. Deng, C.L. Lao, M. Li, S.F. Lin, X. Luo, L.J. Shan, X. Shen, H. Wang, J. Wang, Y. Xu, L.G. Yan, X. Yang, K. Zhou
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
  • Y.H. Dou, X.J. Shu
    Institute of Applied Physics and Computational Mathematics, People's Republic of China
  • W.-H. Huang
    TUB, Beijing, People's Republic of China
  • X.Y. Lu
    PKU, Beijing, People's Republic of China
 
  Funding: Work supported by China National Key Scientific Instrument and Equipment Development Project (2011YQ130018), National Natural Science Foundation of China (11475159, 11505173, 11575264 and 11605190)
The stimulated saturation of the terahertz free electron laser at China Academy of Engineering Physics was reached in August, 2017. This THz FEL facility consists of a GaAs photocathode high-voltage DC gun, a superconducting RF linac, a planar undulator and a quasi-concentric optical resonator. The terahertz wave frequency is continuous adjustable from 2 THz to 3 THz. The average power is more than 10 W and the micro-pulse power is more than 0.3 MW.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF044  
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TUPMF045 Performance Optimization of a Prototype Undulator U38 Using Multi-Objective Genetic Algorithm undulator, MMI, electron, free-electron-laser 1353
 
  • L.G. Yan, D.R. Deng, P. Li, D. Wu
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
 
  Funding: The project of the national large-scale instrument development: 2011YQ130018; National Natural Science Foundation of China: 11505174, 11505173 and 11605190.
Genetic Algorithm (GA) is one of the most excellent method to search the optimal solution of a problem, which has been applied to solve various problems. It is hard to estimate shim applied on raw undulator precisely. There are many methods have been developed to solve the problem. In this proceeding, we measured the magnetic field distribution of prototype undulator U38 and concluded the shim using multi-objective GA. The code was written with the language of Python and based on the package pyevolve. A multi-objective fitness function was setup to implement the multi-objective optimization. Experimentally,performances satisfied the requirements by shimming U38 three times. The trajectory center deviation, peak-to-peak error and phase error are reduced to 0.15 mm, 0.49% and 1°.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF045  
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TUPMF051 Generating Ultrashort X-Ray Pulse in a Diffraction-Limed Storage Ring by Phase-Merging Enhanced Harmonic Generation with Normal Modulator bunching, radiation, electron, undulator 1371
 
  • W. Liu, Y. Jiao
    IHEP, Beijing, People's Republic of China
 
  In recent years, the study of ultrafast processes has increased the demand for ultrashort pulses. The duration of the synchrotron radiation pulse is generally in the range of 10-100 ps, which cannot be used in the experiments of studying the ultrafast process. Thus it is interesting to explore a way of obtaining sub-picosecond radiation pulses in storage ring light sources. The phase-merging enhanced harmonic generation (PEHG) scheme using a transverse gradient undulator as the modulator can be used to generate coherent radiation at high harmonic, which is very suitable for the generating ultrashort pulses in a diffraction-limed storage ring (DLSR). This paper presents a new PEHG modulation scheme, using a normal undulator as the modulator. This scheme is technically easier to be realized in a DLSR. Simulation is performed to demonstrate the effectiveness of this method.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF051  
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TUPMF076 Temporal X-ray Reconstruction Using Temporal and Spectral Measurements electron, simulation, photon, FEL 1440
 
  • F. Christie, J. Rönsch-Schulenburg, M. Vogt
    DESY, Hamburg, Germany
  • Y. Ding, Z. Huang, J. Krzywinski, A.A. Lutman, T.J. Maxwell, D.F. Ratner
    SLAC, Menlo Park, California, USA
  • V. A. Jhalani
    CALTECH, Pasadena, California, USA
 
  Transverse deflecting structures (TDS) are widely used in accelerator physics to measure the longitudinal density of particle bunches. When used in combination with a dispersive section, the whole longitudinal phase space density can be imaged. At the Linac Coherent Light Source (LCLS), the installation of such a device downstream of the undulators enables the reconstruction of the X-ray temporal intensity profile by comparing longitudinal phase space distributions with lasing on and lasing off*. However, the resolution of this TDS is limited to around 1 fs rms (root mean square), and therefore, in most cases, it is not possible to resolve single self-amplified spontaneous emission (SASE) spikes within one photon pulse. By combining the intensity spectrum from a high resolution photon spectrometer** and the temporal structure from the TDS, the overall resolution is enhanced, thus allowing the observation of temporal, single SASE spikes. The combined data from the spectrometer and the TDS is analyzed using an iterative algorithm to obtain the actual intensity profile. In this paper, we present the reconstruction algorithm as well as analyzed data obtained from simulations which shows the reliability of this method. Real data will be published at a later stage.
*Y. Ding et al., Phys. Rev. ST AB, 14, 120701, 2011.
**D. Zhu et al., Appl. Phys. Lett., 101, 034103, 2012.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF076  
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TUPMF078 Control of FEL Radiation Properties by Tailoring the Seed Pulses FEL, experiment, electron, simulation 1444
 
  • V. Grattoni, R.W. Aßmann, J. Bödewadt, I. Hartl, C. Lechner, B. Manschwetus, M.M. Mohammad Kazemi
    DESY, Hamburg, Germany
  • A. Azima, W. Hillert, V. Miltchev, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Khan, T. Plath
    DELTA, Dortmund, Germany
 
  Seeded free-electron lasers (FELs) produce intense, ultrashort and fully coherent X-ray pulses. These seeded FEL pulses depend on the initial seed properties. Therefore, controlling the seed laser allows tailoring the FEL radiation for phase-sensitive experiments. In this contribution, we present detailed simulation studies to characterize the FEL process and to predict the operation performance of seeded pulses. In addition, we show experimental data on the temporal characterization of the seeded FEL pulses performed at the sFLASH experiment in Hamburg.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF078  
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TUPMF079 An Option to Generate Seeded FEL Radiation for FLASH1 FEL, electron, undulator, radiation 1448
 
  • V. Grattoni, R.W. Aßmann, J. Bödewadt, I. Hartl, C. Lechner, B. Manschwetus, M.M. Mohammad Kazemi
    DESY, Hamburg, Germany
  • W. Hillert, V. Miltchev, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Khan, T. Plath
    DELTA, Dortmund, Germany
 
  The FLASH free-electron laser (FEL) at DESY is currently operated in self-amplified spontaneous emission (SASE) mode in both beamlines FLASH1 and FLASH2. Seeding offers unique properties for the FEL pulse, such as full coherence, spectral and temporal stability. In this contribution, possible ways to carry the seeded FEL radiation to the user hall are presented with analytical considerations and simulations. For this, components of the sFLASH seeding experiment are used.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF079  
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TUPMF081 Microphonic Detuning Induced Coupler Kick Variation at LCLS-II cavity, linac, free-electron-laser, beam-loading 1456
 
  • T. Hellert
    DESY, Hamburg, Germany
  • W. Ackermann, H. De Gersem
    TEMF, TU Darmstadt, Darmstadt, Germany
  • C. Adolphsen, Z. Li, C.E. Mayes
    SLAC, Menlo Park, California, USA
 
  The LCLS-II free-electron laser will be an upgrade of the existing Linac Coherent Light Source (LCLS), including a 4 GeV CW superconducting linac based on the TESLA technology. The high quality factor of the cavity makes it very sensitive to vibrations. The shift of its eigenfrequency (i.e., detuning) will be compensated by the power source in order to assure a constant accelerating voltage. Significant variations of the forward power are expected which result in coupler kick variations induced by the fundamental power coupler. In this work we estimate the magnitude of trajectory jitter caused by these variations. High precision 3D field maps including standing and traveling-wave components for a cavity with the LCLS-II coupler design are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF081  
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TUPMF082 FLASHForward: DOOCS Control System for a Beam-Driven Plasma-Wakefield Acceleration Experiment controls, timing, detector, hardware 1460
 
  • S. Karstensen, S. Bohlen, J. Dale, M. Dinter, J.M. Müller, P. Niknejadi, J. Osterhoff, K. Poder, P. Pourmoussavi, V. Rybnikov, L. Schaper, B. Schmidt, J.-P. Schwinkendorf, B. Sheeran, G.E. Tauscher, S. Thiele, S. Wesch, P. Winkler
    DESY, Hamburg, Germany
 
  The FLASHForward project at DESY is an innovative beam-driven plasma-wakefield acceleration experiment integrated in the FLASH facility, aiming to accelerate electron beams to GeV energies over a few centimetres of ionised gas. These accelerated beams are tested for their capability to demonstrate exponential free-electron laser gain; achievable only through rigorous analysis of both the driver and witness beam's phase space. The thematic priority covered in here the control system part of FLASHForward. To be able to control, read out and save data from the diagnostics into DAQ, the DOOCS control system has been integrated into FLASH Forward. Laser beam control, over 70 cameras, ADCs, timing system and motorised stages are combined into the one DOOCS control system as well as vacuum and magnet controls. Micro TCA for Physics (MTCA.4) is the solid basic computing system, supported from high power workstations for camera read-out and normal Linux computers.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF082  
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TUPMF085 Status of the sFLASH Experiment FEL, electron, photon, experiment 1471
 
  • C. Lechner, R.W. Aßmann, J. Bödewadt, V. Grattoni, I. Hartl, T. Laarmann, M.M. Mohammad Kazemi, A. Przystawik
    DESY, Hamburg, Germany
  • A. Azima, H.B. Biss, M. Drescher, W. Hillert, L.L. Lazzarino, V. Miltchev, J. Roßbach
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Khan, T. Plath
    DELTA, Dortmund, Germany
 
  Funding: This work is supported by the Federal Ministry of Education and Research of Germany within FSP-302 under FKZ 05K13GU4, 05K13PE3, and 05K16PEA.
The sFLASH experiment at the free-electron laser (FEL) FLASH1 is a setup for the investigation of external FEL seeding. Since 2015, the seeding scheme high-gain harmonic generation (HGHG) is being studied. At the end of the seeded FEL, an RF deflector enables time-resolved analysis of the seeded electron bunches while the photon pulses can be characterized using the technique of THz streaking. In this contribution, we present the current configuration of the experiment and give an overview of recent experimental results.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF085  
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TUPMF089 Possible Upgrades of FLASH –- A View from the Accelerator-Perspective undulator, FEL, optics, electron 1477
 
  • M. Vogt, B. Faatz, K. Honkavaara, J. Rönsch-Schulenburg, S. Schreiber, J. Zemella
    DESY, Hamburg, Germany
 
  Recently FLASH (Free electron LASer in Hamburg) at DESY has been granted funding for a refurbishment project covering among others the replacement of two old SRF modules, an upgrade of the injector lasers and an upgrade of parts of the electron beam diagnostics. In addition we are proposing several possible upgrades and new features for the injector and the drive linac as well as in the undulator beamlines. Here we present options which are in our opinion technically feasible and at the same time operationally manageable.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF089  
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TUPMF090 Status of the Superconducting Soft X-Ray Free-Electron Laser FLASH at DESY FEL, operation, undulator, electron 1481
 
  • M. Vogt, K. Honkavaara, M. Kuhlmann, J. Rönsch-Schulenburg, S. Schreiber, R. Treusch
    DESY, Hamburg, Germany
 
  FLASH, the free-electron laser (FEL) user facility at DESY, has delivered high brilliance VUV and soft x-ray FEL radiation for photon experiments since summer 2005. In 2014 and 2015 a second beamline, FLASH2, has been commissioned in parallel to user operation at FLASH1. FLASH's superconducting linac can produce bunch trains of up to 800 bunches within a 0.8 ms RF flat top at a repetition rate of 10 Hz. In standard operation during 2017 FLASH supplied up to 500 bunches in two bunch trains with independent fill patterns and compression schemes. Since mid 2017 initial commissioning of a third experimental beamline, accommodating the FLASHForward plasma wakefield acceleration experiment, has started. We report on the highlights of the FLASH operation in 2017/2018.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF090  
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TUPMK008 Highly-stable, High-power Picosecond Laser Optically Synchronized to a UV Photocathode Laser for an ICS Hard X-ray Generation timing, cathode, electron, linac 1504
 
  • K.-H. Hong
    MIT, Cambridge, Massachusetts, USA
  • D. Gadonas, L.M. Hand, K. Neimontas, A. Senin, V. Sinkevicius
    Light Conversion, Vilnius, Lithuania
  • W.S. Graves, M.R. Holl, L.E. Malin, C. Zhang
    Arizona State University, Tempe, USA
  • S. Klingebiel, T. Metzger, K. Michel
    TRUMPF Scientific Lasers GmbH + Co. KG, Munchen-Unterfoehring, Germany
 
  Under the CXLS project at Arizona State University we are developing an inverse Compton scattering (ICS) hard X-ray source* towards a compact XFEL with electron nano-bunching. The ICS interaction is critically dependent on the quality of driver pulses such as: 1) available peak intensity, 2) energy/pointing stability, and 3) relative timing stability to UV pulses initially triggering electron beams. Here, we report on a highly stable, 1 kHz, 200 mJ, 1.1 ps, 1030 nm laser with good beam quality as an ICS driver, optically synchronized to a UV photocathode laser. The ICS driver is based on a Yb:YAG thin-disk regenerative amplifier (RGA), ensuring an excellent energy stability (shot-to-shot 0.52% rms; 0.14% rms over 24 hours). The pointing stability better than 4 urad is obtained. The M2 factor is as good as ~1.5 at the full energy, leading to the achievable laser intensity of >1017 W/cm2 with f/10 focusing. The photocathode laser, a frequency-quadrupled Yb:KGW RGA, share a common seed oscillator with the ICS driver for optical synchronization. The residual sub-ps timing drift is further reduced to 33 fs rms using an optical locking scheme based on a parametric amplifier.
* W.S. Graves et al., "Compact X-ray source based on burst mode inverse compton scattering at 100 kHz," Phys. Rev. ST Accel. Beams, Vol. 17, p. 120701 (Dec. 2014).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK008  
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TUPMK009 Electron Beam Optics for the ASU Compact XFEL dipole, FEL, simulation, electron 1507
 
  • C. Zhang, W.S. Graves, M.R. Holl, L.E. Malin
    Arizona State University, Tempe, USA
  • E.A. Nanni
    SLAC, Menlo Park, California, USA
 
  Funding: National Science Foundation Division of Physics (Accelerator Science) award 1632780, award 1231306. DOE grant DE-AC02-76SF00515.
Arizona State University (ASU) is pursuing a new concept for a compact x-ray FEL (CXFEL) as a next phase of compact x-ray light source (CXLS). We describe the electron beam optics design for the ASU compact XFEL. In previous experiments we introduced a grating diffraction method to generate a spatially modulated beam. We plan to combine a telescope imaging system with emittance exchange (EEX) to magnify/demagnify the modulated beam and transfer it from transverse modulation into a longitudinal one to make it an ideal seed for phase-coherent XFEL. The simulation results of the beam line setup will be demonstrated. Our first goal is to successfully image the modulated beam with desired magnification then we will investigate various magnification and magnets combinations and optimize aberration correction.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK009  
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TUPML006 Updates of the Argonne Cathode Test-stand cathode, electron, gun, experiment 1542
 
  • J.H. Shao, M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.F. Power, C. Whiteford, E.E. Wisniewski, L.M. Zheng
    ANL, Argonne, Illinois, USA
  • S.P. Antipov, G. Chen, E. Gomez, C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S.V. Baryshev
    Michigan State University, East Lansing, Michigan, USA
 
  The Argonne Cathode Test-stand (ACT) is a unique testbed to develop cathodes and to conduct fundamental surface study under ultra-high rf field (up to 700 MV/m with pin-shaped cathodes). The test-stand consists of an L-band 1.3 GHz single-cell photocathode rf gun and a field emission (FE) imaging system to locate emitters with a resolution of ∼20 𝜇m. In the recent upgrade, UV laser has been introduced to improve the imaging system and to significantly expand the ACT towards photoemission and laser-assisted field emission research. In addition, a load-lock system has been added to the beam line to expedite the cathode switching period. The paper will present details of the upgrade as well as experiments planned in the near future.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML006  
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TUPML014 CO2 CPA Laser Development for User Experiments in Advanced Accelerators and Radiation Sources experiment, plasma, optics, operation 1556
 
  • M.N. Polyanskiy, M. Babzien, M.A. Palmer, I. Pogorelsky
    BNL, Upton, Long Island, New York, USA
 
  The ATF* is a National User Facility for advanced research in accelerator physics and technology. The ATF's terawatt CO2 laser is a unique scientific instrument allowing researchers to explorer new particle acceleration mechanisms and to study light/matter interaction at an order-of-magnitude longer photon wavelengths compared to the majority of other laser research facilities (λ≈10μm). Continuous development over more than two decades brought the ATF's CO2 laser to the limit of peak power achievable in a conventional gas laser MOPA configuration (in ATF's amplifier geometry this is ~0.5 TW in routine operation, and up to 2 TW in some experiments). To overcome this limit, we employ, for the first time in a gas laser, a chirped-pulse amplification (CPA) scheme. The goal of our current research and development effort is to demonstrate 3-5 TW peak power at the system output and to reliably deliver a large fraction of this power as a high-quality beam to a range of user experiments. Achieving this goal will lay the ground work for implementation of a >10 TW mid-IR laser system "BESTIA" that is currently being constructed as a part of the ATF-II project.
*Accelerator Test Facility at Brookhaven National Laboratory
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML014  
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TUPML015 Influence of Ionization and Beam Quality on Interaction of Tw-Peak Co2 Laser With Hydrogen Plasma plasma, simulation, electron, experiment 1560
 
  • P. Kumar, V. Samulyak
    SBU, Stony Brook, USA
  • V. Samulyak, K. Yu
    BNL, Upton, Long Island, New York, USA
 
  3D numerical simulations of the interaction of a powerful CO2 laser with hydrogen jets demonstrating the role of ionization and laser beam quality are presented. Simulations are performed in support of the plasma wakefield accelerator experiments being conducted at the BNL Accelerator Test Facility (ATF). The CO2 laser at BNL ATF has several potential advantages for laser wakefield acceleration compared to widely used solid-state lasers. SPACE, a parallel relativistic Particle-in-Cell code, developed at SBU and BNL, has been used in these studies. A novelty of the code is its set of efficient atomic physics algorithms that compute ionization and recombination rates on the grid and transfer them to particles. The primary goal of the initial BNL experiments was to characterize the plasma density by measuring the sidebands in the spectrum of the probe laser. Simulations, that resolve hydrogen ionization and laser spectra, help explain several trends that were observed in the experiments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML015  
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TUPML019 Design of Multi-Alkali Photocathode Preparation System for CTFEL Facility cathode, FEL, vacuum, electron 1571
 
  • D.X. Xiao, M. Li, Q. Pan, H. Wang, X. Yang
    CAEP/IAE, Mianyang, Sichuan, People's Republic of China
 
  The first saturated lasing of the China Academy of Engineering Physics tera-hertz free electron laser (CTFEL) facility has been realized. In order to improve the performance of the CTFEL facility, the multi-alkali photocathode with much longer life-time has been proposed to replace the GaAs photocathode currently used. This paper presents the design of the multi-alkali photocathode preparation system, which consists of three chambers: the suitcase chamber, the preparation chamber, and the loading chamber. The function of each chamber is also discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML019  
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TUPML021 A Beamline Design to Transport Laser Wakefield Electrons to a Transverse Gradient Undulator electron, undulator, quadrupole, plasma 1577
 
  • K.A. Dewhurst, H.L. Owen
    UMAN, Manchester, United Kingdom
  • E. Brunetti, D.A. Jaroszynski, S.M. Wiggins
    USTRAT/SUPA, Glasgow, United Kingdom
  • B.D. Muratori
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • B.D. Muratori
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Funding: This work was supported by the UK Science and Technology Facilities Council, Grant No. ST/G008248/1.
The Cockcroft Beamline is to be installed at the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA). The beamline is designed to transport 1 GeV electrons from a laser wakefield acceleration (LWFA) source to a pair of transverse gradient undulators. The project aims to produce X-ray undulator radiation in the first phase and free-electron laser (FEL) radiation in the second phase. The total beamline will be less than 23 m long, thus the Cockcroft Beamline has the potential to be the UK's first compact X-ray FEL. Here we present the main features of the beamline design.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML021  
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TUPML026 Multi-photon Photoemission and Ultrafast Electron Heating in Cu Photocathodes at Threshold electron, photon, cathode, radiation 1593
 
  • J. Bae, L. Cultrera
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • I.V. Bazarov, J.M. Maxson
    Cornell University, Ithaca, New York, USA
  • S.S. Karkare, H.A. Padmore
    LBNL, Berkeley, California, USA
  • P. Musumeci, X.L. Shen
    UCLA, Los Angeles, California, USA
 
  Funding: U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams.
Operating photocathodes near the photoemission threshold holds the promise of yielding small intrinsic emittance, at the cost of significantly reduced quantum efficiency. In modern femtosecond photoemission electron sources, this requires a very high intensity (10s of GW/cm2) to extract a useful quantity of electrons. At this intensity, the electron occupation function is far from equilibrium and evolves rapidly on sub-ps timescales. Thus, ultrafast laser heating and multiphoton photoemission effects may play a significant role in emission, thereby increasing the minimum achievable emittance. In this work, we use a Boltzmann equation approach to calculate the non-equilibrium occupation function evolution in time for a copper photocathode, yielding a prediction of quantum efficiency and mean transverse energy as a function of input intensity.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML026  
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TUPML027 Barium Tin Oxide Ordered Photocathodes: First Measurements and Future Perspectives electron, photon, cathode, emittance 1597
 
  • A. Galdi, E. B. Lochocki, H. Paik, C.T. Parzyck, D. G. Schlom, K.M. Shen
    Cornell University, Ithaca, New York, USA
  • G. Adhikari, W.A. Schroeder
    UIC, Chicago, Illinois, USA
  • I.V. Bazarov, L. Cultrera, W. H. Li, J.M. Maxson, C. M. Pierce
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams.
Single crystalline photocathodes with small electron effective mass are supposed to enable ultra-low emittance beams, by taking advantage of the conservation of transverse (crystal) momentum. We present a preliminary study on photoemission from epitaxial films of La-doped BaSnO3 with (100) orientation. We demonstrate here the possibility of generating and characterizing electron beams by exciting photoelectrons solely from the conduction band. We report quantum efficiency and mean transverse energy meaurements as a function of photon energy from the bare and Cs-activated La-doped BaSnO3 surface.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML027  
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TUPML031 Characterization of Polarization-Dependent Emittance From an Array of Au Nanorods using Velocity Map Imaging Spectrometer electron, polarization, emittance, experiment 1612
 
  • H. Ye, F.X. Kärtner, S. T. Trippel
    Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
  • A. Fallahi, J. Küpper, O. Muecke
    CFEL, Hamburg, Germany
  • F.X. Kärtner
    MIT, Cambridge, Massachusetts, USA
  • F.X. Kärtner, J. Küpper, S. T. Trippel, H. Ye
    The Hamburg Center for Ultrafast Imaging, University of Hamburg, hamburg, Germany
  • J. Küpper, G.M. Rossi
    DESY, Hamburg, Germany
  • H. Ye
    University of Hamburg, Hamburg, Germany
 
  Electron beams of high quality, e.g., low emittance, are of crucial importance for cutting-edge scientific instruments, such as x-ray free electron lasers (XFELs) and ultrafast electron diffraction (UED) setups. A velocity-map-imaging (VMI) spectrometer was implemented to characterize the intrinsic root-mean-square (rms) normalized emittance from photocathodes. The spectrometer operated in both, spatial map imaging (SMI) and VMI modes. Therefore, spatial- and velocity-coordinates were recorded independently and quickly. The technique allows for fast complete emittance measurements, within minutes. A 75 μm pitch array of Au nanorods of dimension 100×30~nm, was studied under strong-field-emission regime by 100 fs 1 kHz 1.3 μm laser pulses with a 300×30 μm2 focus spot size on the sample. A patterned electron bunch was observed, each emitted from a single nanorod within the array. A polarization dependent photoemission study was performed showing a smaller rms-normalized divergence of 0.8 mrad with the laser polarization normal to the sample surface, compared to 1.15 mrad for the parallel case.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML031  
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TUPML035 FELs Driven by Laser Plasma Accelerators Operated with Transverse Gradient Undulators undulator, FEL, electron, radiation 1615
 
  • F. Jafarinia, R.W. Aßmann, F. Burkart, U. Dorda, C. Lechner, B. Marchetti, R. Rossmanith, P.A. Walker
    DESY, Hamburg, Germany
  • A. Bernhard, R. Rossmanith
    KIT, Karlsruhe, Germany
 
  Laser Plasma Accelerators produce beams with a significantly higher energy spread (up to a few percent) compared to conventional electron sources. The high energy spread increases significantly the gain length when used for an FEL. In order to reduce the gain length of the FEL the Transverse Gradient Undulators (TGUs) instead of conventional undulators were proposed. In this paper the limits of this concept are discussed using a modified Version of the GENESIS program*.
*Zhirong Huang et al., Phys. Rev. Lett., 109, 204801
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML035  
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TUPML036 ALEGRO, the Advanced LinEar collider study GROup collider, plasma, linear-collider, acceleration 1619
 
  • P. Muggli
    MPI, Muenchen, Germany
  • B. Cros
    CNRS LPGP Univ Paris Sud, Orsay, France
 
  We briefly describe activities of ALEGRO, the Advanced LinEar collider study GROup.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML036  
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TUPML038 Simulation of Phase-Dependent Transverse Focusing in Dielectric Laser Accelerator Based Lattices lattice, focusing, emittance, quadrupole 1622
 
  • F. Mayet, R.W. Aßmann, U. Dorda, W. Kuropka
    DESY, Hamburg, Germany
  • W. Kuropka, F. Mayet
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Funding: Gordon and Betty Moore Foundation. Grant GBMF4744
The Accelerator on a CHip International Program (ACHIP) funded by the Gordon and Betty Moore Foundation aims to demonstrate a prototype of a fully integrated accelerator on a microchip based on laser-driven dielectric structures until 2021. Such an accelerator on a chip needs all components known from classical accelerators. This includes an electron source, accelerating structures and transverse focusing arrangements. Since the period of the accelerating field is connected to the drive laser wavelength of typically a few microns, not only longitudinal but also transverse effects are strongly phase-dependent even for few femtosecond long bunches. If both the accelerating and focusing elements are DLA-based, this needs to be taken into account. In this work we study in detail the implications of a phase-dependent focusing lattice on the evolution of the transverse phase space of a transported bunch.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML038  
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TUPML039 First Order Sensitivity Analysis of Electron Acceleration in Dual Grating Type Dielectric Laser Accelerator Structures electron, simulation, experiment, emittance 1626
 
  • F. Mayet, R.W. Aßmann, U. Dorda, W. Kuropka
    DESY, Hamburg, Germany
  • W. Kuropka, F. Mayet
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Funding: Gordon and Betty Moore Foundation. Grant GBMF4744
Symmetrically driven dual-grating type DLA (Dielectric Laser Accelerator) linac structures allow for in-channel electric field gradients on the order of GV/m at optical wavelengths. In this work we study the sensitivity of important final beam parameters like mean energy, energy spread and transverse emittance on DLA drive laser as well as input beam parameters. To this end a fast specialized particle tracking code (DLATracker) is used to compute the so called first order sensitivity indices based on a large number of Monte Carlo simulation runs of an exemplary external injection based DLA experiment. The results of this work point out important stability constraints on the drive laser setup and the externally injected electron beam.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML039  
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TUPML040 Status of the Transverse Diagnostics at FLASHForward plasma, electron, wakefield, diagnostics 1630
 
  • P. Niknejadi, R.T.P. D'Arcy, A. Knetsch, V. Libov, A. Martinez de la Ossa, J. Osterhoff, K. Poder, L. Schaper
    DESY, Hamburg, Germany
  • M. Kaluza, M.B. Schwab, A. Sävert, C. Wirth
    IOQ, Jena, Germany
  • M. Kaluza
    HIJ, Jena, Germany
  • T.J. Mehrling
    LBNL, Berkeley, USA
  • C.A.J. Palmer
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
 
  Funding: Helmholtz Institute, Bundesministerium für Bildung und Forschung, and European Union‘s Horizon 2020 research and innovation program.
Density modulations in plasma caused by a high-intensity laser or a high charge density electron pulse can generate extreme acceleration fields. Acceleration of electrons in such fields may produce ultra-relativistic, quasi-monoenergetic, ultra-short electron bunches over distances orders of magnitudes shorter than in state-of-the-art radio-frequency accelerators. FLASHForward is such a beam-driven plasma wakefield accelerator (PWFA) project at DESY with the goal of producing, characterizing, and utilizing such beams. Temporal characterization of the acceleration process is of crucial importance for improving the stability and control in PWFA beams. While measurement of the transient field of the femtosecond bunch in a single shot is challenging, in recent years novel techniques with great promise have been developed** ***. This work discusses the plans and status of the transverse diagnostics at FLASHForward.
*A. Aschikhin et. al., NIMA , Volume 806 (11 January 2016) pp. 175-183.
**A. Buck et al., Nature Physics 7, (2011) 543.
***C. J. Zhang et al., Phys. Rev. Lett. 119 (2017) 064801.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML040  
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TUPML041 Two-Stage Laser-Driven Plasma Acceleration With External Injection for EuPRAXIA plasma, electron, acceleration, wakefield 1634
 
  • E.N. Svystun, R.W. Aßmann, U. Dorda, A. Ferran Pousa, T. Heinemann, B. Marchetti, P.A. Walker, M.K. Weikum, J. Zhu
    DESY, Hamburg, Germany
  • A. Ferran Pousa, T. Heinemann, A. Martinez de la Ossa
    University of Hamburg, Hamburg, Germany
  • T. Heinemann
    USTRAT/SUPA, Glasgow, United Kingdom
 
  The EuPRAXIA (European Particle Research Accelerator with eXcellence In Applications) project aims at producing a conceptual design for the worldwide plasma-based accelerator facility, capable of delivering multi-GeV electron beams with high quality. This accelerator facility will be used for various user applications such as compact X-ray sources for medical imaging and high-energy physics detector tests. EuPRAXIA explores different approaches to plasma acceleration techniques. Laser-driven plasma wakefield acceleration with external injection of an RF-generated electron beam is one of the basic research directions of EuPRAXIA. We present studies of electron beam acceleration to GeV energies by a two-stage laser wakefield acceleration with external injection from an RF accelerator. Electron beam injection, acceleration and extraction from the plasma, using particle-in-cell simulations, are investigated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML041  
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TUPML045 Segmented Terahertz Driven Device for Electron Acceleration electron, acceleration, linac, controls 1642
 
  • D. Zhang
    DESY, Hamburg, Germany
  • A-L. Calendron, H. Cankaya, M. Fakhari, A. Fallahi, Y. Hua, N.H. Matlis, X. Wu, L.E. Zapata
    CFEL, Hamburg, Germany
  • M. Hemmer, F.X. Kärtner
    Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
  • F.X. Kärtner
    MIT, Cambridge, Massachusetts, USA
 
  Funding: ERC Synergy Grant AXSIS (609920), Deutsche Forschungsgemeinschaft (SPP1840 SOLSTICE and CUI EXC1074), and Gordon and Betty Moore foundation (ACHIP GBMF4744)
We present a segmented THz based device (STEAM) capable of performing multiple high-field operations on the 6D-phase-space of ultrashort electron bunches. Using only a few microjoules of single-cycle THz radiation, we have shown record THz-based acceleration of >30 keV of an incoming 55keV electron beam, with a peak acceleration field gradient of around 70 MV/m that is comparable with that from a conventional RF accelerator. It can be scaled up to GV/m gradients that can accelerate electrons into the MeV regime. At the same time, the STEAM device can also manipulate the electrons that show high focusing gradient (2 kT/m), compression of electron bunches down to 100 fs and streaking gradient of 140 µrad/fs, which offers temporal profile characterizations with resolution below 10 fs. The STEAM device can be fabricated with regular mechanical machining tools and supports real-time switching between different modes of operation. It paves the way for the development of THz-based compact electron guns, accelerators, ultrafast electron diffractometers and Free-Electron Lasers.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML045  
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TUPML047 Optimisation of High Transformer Ratio Plasma Wakefield Acceleration at PITZ plasma, wakefield, acceleration, electron 1648
 
  • G. Loisch, P. Boonpornprasert, J.D. Good, M. Groß, H. Huck, M. Krasilnikov, O. Lishilin, A. Oppelt, Y. Renier, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • R. Brinkmann, A. Martinez de la Ossa, J. Osterhoff
    DESY, Hamburg, Germany
  • F.J. Grüner
    CFEL, Hamburg, Germany
  • F.J. Grüner, A. Martinez de la Ossa
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  The transformer ratio, the ratio between maximum accelerating field and maximum decelerating field in the driving bunch of a plasma wakefield accelerator (PWFA), is one of the key aspects of this acceleration scheme. It not only defines the maximum possible energy gain of the PWFA but it is also connected to the maximum percentage of energy that can be extracted from the driver, which is a limiting factor for the efficiency of the accelerator. Since in linear wakefield theory a transformer ratio of 2 cannot be exceeded with symmetrical drive bunches, any ratio above 2 is considered high. After the first demonstration of high transformer ratio acceleration in a plasma wakefield at PITZ, the photoinjector test facility at DESY, Zeuthen site, limiting aspects of the transformer ratio are under investigation. This includes e.g. the occurrence of bunch instabilities, like the transverse two stream instability, or deviations of the experimentally achieved bunch shapes from the ideal.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML047  
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TUPML054 Microbeam Irradiation System with a Dielectric Laser Accelerator for Radiobiology Research electron, accelerating-gradient, radiation, cavity 1664
 
  • K. Koyama
    KEK, Ibaraki, Japan
  • Z. Chen
    The University of Tokyo, Tokyo, Japan
  • T. Takahashi
    The University of Tokyo, The School of Engineering, Tokyo, Japan
  • M. Uesaka
    The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
 
  Funding: This work was supported by KAKENHI (Grant-in-Aid for Scientific Research)15H03595 and partly supported by NIMS Nanofabrication Platform in Nanotechnology Platform Project sponsored by the MEXT, Japan.
A laser micro-irradiation (LMI) system is widely used in the field of radiobiology because of its acceptably small size. However, damage in a cell nucleus caused by the LMI system does not necessarily simulate a radiation effect. If the laser of the LMI system is replaced with a small-scale 1MeV-class accelerator such as a dielectric laser accelerator (DLA), experiments might be performed under conditions that are more realistic. The desirable configuration of the DLA for a compact micro-beam irradiation system is that laser pulses are transported to a dielectric structure by single-mode optical fibers and the laser energy is accumulated in an accelerator channel. The long and low-intensity laser pulse of 100 MW/cm2, 10ps and a resonator with Q=104 are capable of producing the light intensity of 1 TW/cm2. The long laser pulse, i.e., low laser induced damage threshold intensity, decreases the acceleration gradient to about 1/3 of the ultra-short pulse irradiation of 100 fs. The length of the accelerator at long-laser pulse might be within the allowable range of several cm. The resonator scheme is useful only for the sub-relativistic regime because of the acceleration gradient.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML054  
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TUPML059 Slice Energy Spread Optimization for a 5 GeV Laser-Plasma Accelerator plasma, beam-loading, simulation, electron 1670
 
  • X. Li, P.A.P. Nghiem
    IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
  • A. Mosnier
    CEA/IRFU, Gif-sur-Yvette, France
 
  GeV-scale laser-plasma accelerating modules can be integrated into a multi-staged plasma linac for driving compact X-ray light sources or future colliders. Such a plasma module, operating in the quasi-linear regime, has been designed for the 5 GeV laser plasma acceleration stage (LPAS) of the EuPRAXIA project. Although it can be employed to optimize the total energy spread, the beam loading effect introduces an non-negligible slice energy spread to the beam. In this paper, we study the slice energy spread from linear theory, establishing a relationship between it and the laser-plasma parameters. To reduce the slice energy spread, simulations have been carried out for various plasma densities and laser strengths. The results will be discussed and compared with the theory.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML059  
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TUPML061 Study of Mean Transverse Energy of (N)UNCD with Tunable Laser Source solenoid, photon, cathode, electron 1677
 
  • G. Chen
    IIT, Chicago, Illinois, USA
  • G. Adhikari, W.A. Schroeder
    UIC, Chicago, Illinois, USA
  • S.P. Antipov, C.-J. Jing, K. Kovi
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S.V. Baryshev
    ANL, Argonne, Illinois, USA
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  Funding: NSF grant No. NSF-1739150, DOE SBIR program grant No. DE-SC0013145, NSF grant No. PHYS-1535279, DOE Contract No. DE-AC02-06CH11357.
There is a strong motivation to develop and understand novel materials with the potential to be utilized as photocathodes, as these could have desirable photoemission properties for research and industrial applications. Nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) photocathodes have potential to become a material of choice for photocathode applications*. (N)UNCD has high quantum efficiency when processed in hydrogen plasma*, low surface roughness, and high electron conductivity through the bulk**. The mean transverse energy (MTE) was calculated for (N)UNCD thin films using the double-solenoid scan method. (N)UNCD thin film with thickness of 160nm was deposited on highly-doped silicon substrate. Studies of the MTE of a (N)UNCD sample were done using a tunable laser source with photon energies of 3.56 eV to 5.26 eV. These results are presented.
* K.J. Pérez Quintero et al., Appl. Phys. Lett. 105, 123103 (2014).
** S. Bhattacharyya et al., Appl. Phys. Lett. 79, 1441 (2001)
 
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TUPML064 Staged Two Beam Acceleration Beam Line Design for the AWA Facility kicker, experiment, gun, acceleration 1688
 
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  • W. Gai, C.-J. Jing, J.G. Power
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  Funding: This work is funded by the DOE Office of Science, grant no. DE-SC0015479, and contract No. DE-AC02- 06CH11357.
Two beam acceleration is a candidate for future high energy physics machines and FEL user facilities. This scheme consists of two independent electron beam lines operating synchronously. High-charge, 70 MeV drive bunch trains are injected from the RF photo-injector into decelerating structures to generate a few hundred of MW of RF power. This RF power is transferred through an RF waveguide to accelerating structures that are used to accelerate the witness beam. Staging refers to the sequential acceleration (energy gain) in two or more structures on the witness beam line. A kicker was incorporated on the drive beam line to accomplish a modular design so that each accelerating structure can be independently powered by a separate drive beam. Simulations were performed in OPAL-T to model the two beam lines. Beam sizes at the center of the structures was minimized to ensure good charge transmission. The resulting design will be the basis for proof of principle experiments that will take place at the Argonne Wakefield Accelerator (AWA) facility.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML064  
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TUPML070 Laser Ablation Plasma with Solenoid Field Confinement solenoid, plasma, target, ion-source 1706
 
  • G.C. Wang, Q. Jin, L.T. Sun, J. Zhang, X.Z. Zhang, H.W. Zhao, H. Zhao
    IMP/CAS, Lanzhou, People's Republic of China
 
  Funding: This work is supported by National Natural Science Foundation of China (Grant Nos. 11722547, 11605263 and 11505257) and West Light Foundation of The Chi-nese Academy of Sciences (Grant Nos. 29Y637020)
A Laser Ion Source (LIS) can produce high charge state and high intensity ion beams (~emA), especially refracto-ry metallic ion beams, which makes it a promising candi-date as an ion source for heavy ion cancer therapy facili-ties and future accelerator complexes, where pulsed high intensity and high charged heavy ion beams are required. However, it is difficult for LIS to obtain a long pulse width while ensuring high current intensity, thus limiting the application of LIS. To solve the conflict, magnetic fields are proposed to confine the expansion of the laser produced plasma. With a solenoid along the normal direc-tion to the target surface, the lateral adiabatic expansion of the laser ablation plasma is suppressed which extends the pulse width of the ion beam effectively.
 
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TUPML079 A Start to End Simulation of the Laser Plasma Wakefield Acceleration Experiment at ESCULAP plasma, electron, acceleration, wakefield 1731
 
  • K. Wang, C. Bruni, K. Cassou, V. Chaumat, N. Delerue, D. Douillet, S. Jenzer, V. Kubytskyi, P. Lepercq, H. Purwar
    LAL, Orsay, France
  • E. Baynard, M. Pittman
    CLUPS, Orsay, France
  • J. Demailly, O. Guilbaud, S. Kazamias, B. Lucas, G. Maynard, O. Neveu, D. Ros
    CNRS LPGP Univ Paris Sud, Orsay, France
  • D. Garzella
    CEA, Gif-sur-Yvette, France
  • R. Prazeres
    CLIO/ELISE/LCP, Orsay, France
 
  We present a start to end (s2e) simulation of the Laserplasma Wake Field Accelerator (LPWA) foreseen as the ESCULAP project. We use a photo injector to produce a 5 MeV 10 pC electron bunch with a duration of 1 ps RMS, it is boosted to 10 MeV by a S-band cavity and then compressed to 74 fs RMS (30 fs FWHM) by a magnetic compression chicane (dogleg). After the dogleg, a quadrupole doublet and a triplet are utilized to match the Twiss parameters before injecting into the subsequent plasma wakefield. A 40 TW laser is used to excite plasma wakefield in the 10 cm plasma cell. An optimized configuration has been determined yielding at the plasma exit an electron beam at 180 MeV with energy spread of 4.2%, an angular divergence of 0.6 mrad and a duration of 4 fs.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML079  
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WEPAF006 Fast Photodetector Bunch Duration Monitor for the Advanced Photon Source Particle Accumulator Ring detector, synchrotron, linac, photon 1819
 
  • J.C. Dooling, J.R. Calvey, K.C. Harkay, B.X. Yang, C. Yao
    ANL, Argonne, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
A fast photodetector is used to monitor the bunch duration in the Advanced Photon Source (APS) Particle Accumulator Ring (PAR). The Bunch Duration Monitor (BDM) diagnostic provides an accurate measure of the PAR bunch length. PAR BDM data show good agreement with streak camera measurements. The BDM is based on the metal-semiconductor-metal (MSM) photodetector Hamamatsu G4176-03 MSM with specified rise and fall times of 30 ps. The BDM has sufficient frequency response to resolve the PAR bunch near extraction where, under low-charge conditions, minimum rms pulse durations of 200-300 ps are observed. Beam from the PAR is injected into the Booster; for efficient capture, injected rms bunch duration from the PAR must be less than 600 ps. The MSM detector exhibits a ringing response to fast input signals. To overcome this, the BDM output is de-convolved with the impulse response function of the detector-amplifier circuit. Turn-by-turn bunch duration data is presented versus charge and time in the PAR cycle. Charge calibration is used to determine fit parameters for bunch duration measurements in peak-detection mode. Observations relevant to APS Upgrade high-charge studies are presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF006  
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WEPAF043 Commissioning and Long-Term Results of a Fully-Automated Pulse-Based Optical Timing Distribution System at Dalian Coherent Light Source timing, electron, operation, detector 1909
 
  • H.P.H. Cheng, A. Berlin, E. Cano, A. Dai, J. Derksen, D. Forouher, W. Nasimzada, M. Neuhaus, P. Schiepel, E. Seibel, K. Shafak
    Cycle GmbH, Hamburg, Germany
  • Z. Chen, H.L. Ding, Z.G. He, Y.H. Tian, G.R. Wu
    DICP, Dalian, People's Republic of China
  • F.X. Kärtner
    Deutsches Elektronen Synchrotron (DESY) and Center for Free Electron Science (CFEL), Hamburg, Germany
  • B. Liu, X.Q. Liu
    SINAP, Shanghai, People's Republic of China
 
  New generation light sources such as X-ray free-electron lasers* and attoscience centers** require high demand for timing synchronization, on the order of few femtoseconds or below, to generate ultrashort X-ray pulses that enables attosecond temporal and subatomic spatial resolution. The challenge in achieving this scientific dream lies in part in a reliable, high-precision timing distribution system that can synchronize various optical and microwave sources across multi-km distances with good long-term stability. It was shown that the pulsed-optical timing distribution system can deliver sub-fs long-term timing precision between remotely synchronized lasers and microwave sources in laboratory environment.*** We present the latest results from the commissioning of China's first multi-link pulse-based optical timing distribution system (TDS) installed at Dalian Coherent Light Source. Long term operating results of the fully-automated polarization-maintaining TDS, as well as lessons learned and recommendations for future improvements, are presented, including performance of the timing-stabilized PM fiber links, microwave end-stations and ultrafast laser synchronization end-stations.
*http://www.xfel.eu/news/2017/europeanxfelgeneratesitsfirstlaserlight
**G. Mourou and T. Tajima, Science, 331, pp. 41-42, 2011.
***M. Xin et al., Light Sci. Appl., 6, e16187, 2017.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF043  
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WEPAF048 High Resolution and Low Charge Button and Strip-Line Beam Position Monitor Electronics Upgrade at Flash electron, electronics, FEL, operation 1923
 
  • B. Lorbeer, N. Baboi, H.T. Duhme, Re. Neumann
    DESY, Hamburg, Germany
 
  Historically the FLASH (Free Electron Laser in Hamburg) facility at DESY (Deutsches Elektronen-Synchrotron) in Germany has foreseen operation in a charge range from 1nC-3nC for which a VME based BPM(Beam Position Monitor) system has been in operation since 2005. For a couple of years the standard machine operation has been settled at a few hundreds of pC with the tendency for smaller charges down to 100pC and smaller. The availability and resolution performance of the BPM system at charges below 300pC in many locations along the machine was unsatisfactory. In the last couple of years a new BPM electronic system based on the utca standard has been developed to overcome these limitations. A substantially improved version of the analog frontend and digital electronics has been developed in 2016 and tested successfully. During shutdown works at FLASH in summer 2017 all old button and strip-line BPM electronics has been replaced with the new type of electronics. This paper summarizes the features and performance of the new BPM system, compares the beam jitter free resolution of old and new BPM system and highlights its high single shot resolution of better than 10um at a charge of 15pC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF048  
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WEPAF057 Electron Beam Diagnostics Concept for the ELI LUX Project electron, diagnostics, undulator, plasma 1954
 
  • K.O. Kruchinin, D. Kocon, A.Y. Molodozhentsev, L. Pribyl
    ELI-BEAMS, Prague, Czech Republic
  • A. Lyapin
    JAI, Egham, Surrey, United Kingdom
 
  Nowadays the popularity of Laser Wakefield Accelerators (LWFA) is increasingly growing. Although the quality of the beams produced by LWFA is still lower than provided by conventional accelerators, they have great potential to be considered as a new basis for future FELs and even colliders. Laser Undulator X-ray (LUX) source is being commissioned at ELI-beamlines in Czech Republic. The goal of this machine is to provide photon beam in so called "water window" wavelength region for user experiments. Possible upgrade of the facility towards the LWFA based FEL is also considered. The electron beam diagnostics is absolutely crucial for achieving the aim of LUX. Specific properties of the beam produced by current LWFA, such as low charge, poor beam stability, big beam divergence and energy spread, require rethinking and adaptation of the conventional diagnostic tools and, in some cases, development of new ones. Ideally, they have to be compact, stable, non-invasive and allow measurements in single-shot mode. In this report we will present an overview and design considerations for the LUX electron beam main diagnostics. We will also discuss the hardware status and future plans.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF057  
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WEPAF069 Evaluation of Frequency Scanning Interferometer Performances for Surveying, Alignment and Monitoring of Physics Instrumentation alignment, target, luminosity, cavity 1990
 
  • J. Gayde, S.W. Kamugasa
    CERN, Geneva, Switzerland
 
  During the last three years, the performance of Frequency Scanning Interferometry, accurate to a few micrometres, has been evaluated at CERN in the frame of the PACMAN project. Improvements have been studied and tested to make it better suited for typical alignment and survey conditions in accelerators and experiments. The results of these developments and tests, coupled with the multi-channel capability of the system, and its compactness which eases its integration in the area to be surveyed, offer a wide scope of possible applications for in-situ large scale metrology for physics equipment and facility elements. Furthermore, the fact that the system electronics can be placed far away from the position to be measured, allows the system to be used in confined and hazardous spaces. This paper briefly describes the system and its improvements. It gives the precision obtained for distance measurements and for the 3D point reconstruction based on FSI observations in the case of CLIC component fiducialisation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF069  
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WEPAF070 Commissioning of Beam Instrumentation at the CERN AWAKE Facility After Integration of the Electron Beam Line electron, proton, plasma, experiment 1993
 
  • I. Gorgisyan, C. Bracco, S. Burger, S. Döbert, S.J. Gessner, E. Gschwendtner, L.K. Jensen, S. Jensen, S. Mazzoni, D. Medina, K. Pepitone, L. Søby, F.M. Velotti, M. Wendt
    CERN, Geneva, Switzerland
  • M. Cascella, S. Jolly, F. Keeble, M. Wing
    UCL, London, United Kingdom
  • V.A. Verzilov
    TRIUMF, Vancouver, Canada
 
  The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) is a project at CERN aiming to accelerate an electron bunch in a plasma wakefield driven by a proton bunch*. The plasma is induced in a 10 m long Rubidium vapour cell using a pulsed Ti:Sapphire laser, with the wakefield formed by a proton bunch from the CERN SPS. A 16 MeV electron bunch is simultaneously injected into the plasma cell to be accelerated by the wakefield to energies in GeV range over this short distance. After successful runs with the proton and laser beams, the electron beam line was installed and commissioned at the end of 2017 to produce and inject a suitable electron bunch into the plasma cell. To achieve the goals of the experiment, it is important to have reliable beam instrumentation measuring the various parameters of the proton, electron and laser beams such as transverse position, transverse profile as well as temporal synchronization. This contribution presents the status of the beam instrumentation in AWAKE, including the new instruments incorporated into the system for measurements with the electron beam line, and reports on the performance achieved during the AWAKE runs in 2017.
* Gschwendtner E., et al. "AWAKE, the Advanced Proton Driven Plasma Wakefield Experiment at CERN", NIM A 829 (2016)76-82
 
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WEPAK011 Development of the Electron-Beam Diagnostics for the Future BESSY-VSR Storage Ring electron, diagnostics, dipole, storage-ring 2110
 
  • G. Schiwietz, J.G. Hwang, M. Koopmans, M. Ries, A. Schälicke
    HZB, Berlin, Germany
 
  This contribution focusses on the different types of new or improved electron-beam monitors at BESSY II for bunch resolved measurements under future BESSY-VSR conditions. A new diagnostics platform, involving three different dipole beam lines will be built for different di-pole-related optical and THz methods. Our main concepts for robust future monitors for bunch length, beam size and position are presented in the following.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK011  
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WEPAL010 Review of the ELI-NP-GBS Low Level RF and Synchronization Systems LLRF, linac, electron, timing 2162
 
  • L. Piersanti, D. Alesini, M. Bellaveglia, F. Cardelli, M. Diomede, A. Gallo, V. Martinelli
    INFN/LNF, Frascati (Roma), Italy
  • B.B. Baricevic, R. Cerne, G. Jug
    I-Tech, Solkan, Slovenia
  • M. Diomede
    Sapienza University of Rome, Rome, Italy
  • P.N. Dominguez
    Menlo Systems GmbH, Martinsried, Germany
 
  ELI-NP is a linac based gamma-source in construction at Magurele (RO) by the European consortium EuroGammaS led by INFN. Photons with tunable energy and with intensity and brilliance well beyond the state of the art, will be produced by Compton back-scattering between a high quality electron beam (up to 740 MeV) and a 515 nm intense laser pulse. Production of very intense photon flux with narrow bandwidth requires multi-bunch operation at 100 Hz repetition rate. A total of 13 klystrons, 3 S-band (2856 MHz) and 10 C-band (5712 MHz) will power a total of 14 Travelling Wave accelerating sections (2 S-band and 12 C-band) plus 3 S-band Standing Wave cavities (a 1.6 cell RF gun and 2 RF deflectors). Each klystron is individually driven by a temperature stabilized LLRF module for a maximum flexibility in terms of accelerating gradient, arbitrary pulse shaping (e.g. to compensate beam loading effects in multi-bunch regime) and compensation of long-term thermal drifts. In this paper, the whole LLRF system architecture and bench test results, the RF reference generation and distribution together with an overview of the synchronization system will be described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL010  
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WEPAL026 High Repetition Rate, Single-Shot Electro-Optical Monitoring of Longitudinal Electron Bunch Dynamics Using the Linear Array Detector KALYPSO electron, storage-ring, radiation, FEL 2216
 
  • G. Niehues, E. Blomley, M. Brosi, E. Bründermann, M. Caselle, S. Funkner, A.-S. Müller, M.J. Nasse, L. Rota, M. Schuh, P. Schönfeldt, M. Weber
    KIT, Eggenstein-Leopoldshafen, Germany
  • N. Hiller
    PSI, Villigen PSI, Switzerland
 
  Funding: This work is funded by the BMBF contract numbers: 05K13VKA and 05K16VKA.
High repetition rate diagnostics are required when detecting single-shot electro-optical (EO) bunch profiles. The KIT storage ring KARA (KArlsruhe Research Accelerator) is the first storage ring in the world that has a near-field EO bunch-profile monitor in operation. By imprinting longitudinal electron bunch profiles onto chirped laser pulses, single-shot detection is feasible. However, limitations of available detection systems are challenging: The constraints are either given by the repetition rate or the duration of the consecutive acquisitions. Two strategies can overcome these limitations: Based on the photonic time-stretch method, the ps laser pulses can be stretched to the ns range using km long fibers. The readout with a high-bandwidth oscilloscope then enables a single-shot detection at high repetition rates. The other strategy is the development of dedicated ultra-fast photodetector arrays allowing direct detection of the ps pulses at MHz repetition rates. We developed KALYPSO, a linear detector array with a DAQ allowing to record high data-rates over long time scales. Here, we present recent results of studies of the longitudinal electron bunch dynamics using KALYPSO.
 
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WEPAL034 Bunch Length Measurements Using Coherent Smith-Purcell Radiation With Several Gratings at CLIO booster, radiation, detector, experiment 2239
 
  • N. Delerue, S. Jenzer, V. Khodnevych, A. Migayron
    LAL, Orsay, France
  • J.P. Berthet, N. Jestin, J.-M. Ortega, R. Prazeres
    CLIO/ELISE/LCP, Orsay, France
 
  Funding: Financially supported by the Université Paris-Sud (programme "attractivité"), by the French ANR (contract ANR-12-JS05-0003-01) and by IN2P3.
Coherent Smith Purcell radiation allows the measurement of a beam longitudinal profile through the study of the emission spectrum of the radiation emitted when a grating is brought close from the beam. In order to increase the dynamic range of our measurements we have used several gratings and we report on the measured bunch form factor using this technique. We report on these measurements and on the background rejection used.
 
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WEPAL035 The Synchronization System of the Thomx Accelerator linac, HOM, electron, distributed 2243
 
  • N. Delerue, V. Chaumat, R. Chiche, N. ElKamchi, H. Monard, F. Wicek
    LAL, Orsay, France
  • B. Lucas
    CNRS LPGP Univ Paris Sud, Orsay, France
 
  Funding: CNRS and ANR
The ThomX compact light source uses a 50 MeV ring to produce X-rays by Compton scattering. For historical reasons the linac and the ring could not operate at harmonic frequencies of each other. A heterodyne synchronization system has been designed for this accelerator. This synchronization is based on mixing the two RF frequencies to produce an heterodyne trigger signal and that is then distributed to the users. Bench tests of the system has demonstrated a jitter of less than 2 ps. We describe here this synchronization system.
 
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WEPAL040 High Precision Synchronization Development for HiRES, the Ultrafast Electron Diffraction Beamline at LBNL controls, electron, LLRF, gun 2262
 
  • Y. Yang, K.M. Baptiste, M. Betz, L.R. Doolittle, Q. Du, D. Filippetto, G. Huang, F. Ji
    LBNL, Berkeley, California, USA
 
  Precise synchronization between the laser and electron is critical for the pump-probe experiments in the HiRES Ultrafast Electron Diffraction facility. We are upgrading the LLRF and laser control system, which ultimately aims at a synchronization below 50 fs RMS between the pump laser pulse and electron probe at the sample plane. Such target poses tight requirements on the RF field stability both in amplitude and phase, and on the synchronization between the RF field and the laser repetition rate. We are presently developing a new LLRF system that has the potential to decrease the overall noise, reaching the required stability of tens of ppm on RF amplitude and phase. For the laser control side, we are replacing the long coaxial cables with fibers for both control signal transmission and laser signal reception. The control transmission side has been implemented, and the timing jitter has been reduced.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL040  
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WEPAL041 FPGA Based Optical Phase Control for Coherent Laser Pulse Stacking cavity, controls, experiment, FPGA 2265
 
  • Y. Yang, L.R. Doolittle, Q. Du, G. Huang, W. Leemans, R.B. Wilcox, T. Zhou
    LBNL, Berkeley, California, USA
  • A. Galvanauskas
    University of Michigan, Ann Arbor, Michigan, USA
 
  Coherent temporal pulse stacking combines the energy from a train of pulses into one pulse through a series of optical cavities. To stabilize the output energy, the cavity roundtrip phases must be precisely locked to particular values. Leveraging the LLRF expertise we have for conventional accelerators, a FPGA-based control system has been developed for optical cavity phase control. A phase measurement method, ''Modulated Impulse Response'', has been developed and implemented on FPGA. An experiment demonstrated that it can measure and lock the optical phases of four stacking cavities, leading to combination of 25 pulses into one pulse with 1.5 % RMS stability over 30 hours.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL041  
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WEPAL072 A Novel Longitudinal Laserwire to Non-Invasively Measure 6-Dimensional Bunch Parameters at High Current Hydrogen Ion Accelerators emittance, detector, linac, simulation 2349
 
  • S.M. Gibson, A. Bosco
    Royal Holloway, University of London, Surrey, United Kingdom
  • S.E. Alden, A. Bosco, S.M. Gibson
    JAI, Egham, Surrey, United Kingdom
  • A.P. Letchford
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  • J.K. Pozimski
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  • J.K. Pozimski
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
 
  Funding: We acknowledge funding by the STFC Grant ST/P003028/1 and the John Adams Institute at Royal Holloway, University of London.
Optical methods for non-invasive beam diagnostics of high current H ion accelerators have been developed in recent years*, **. Such laserwires typically measure a 1D beam profile and/or 2D transverse emittance from the products of photo-detached ions as a laser beam is scanned across the H beam. For laser pulse durations (~80ns) longer than the RF period (~3ns), the detector integrates many complete bunches, enabling only transverse beam monitoring. This paper presents a new technique to capture a series of time resolved transverse emittance measurements along the bunch train. A fast (~10ps) pulsed laser photo-detaches ions within each bunch and is synchronized to sample consecutive bunches at certain longitudinal positions along each bunch. A fast detector records the spatial distribution and time-of-flight of the neutralized H0, thus both the transverse and longitudinal emittance are reconstructed. We present simulations of a time varying pulsed laser field interacting within an H bunch, and estimate the yield, spatial and time distributions of H0 arriving at the detector. We summarise the design of a recently funded longitudinal laserwire being installed in FETS at RAL, UK.
* NIM-A, 830, p526-531, T. Hofmann et al
** T. Hofmann et al, 'Commissioning of the Operational Laser Emittance Monitors for LINAC4 at CERN' IPAC18.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL072  
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WEPAL073 Enhanced Bunch Monitoring by Interferometric Electro-Optic Methods pick-up, proton, polarization, optics 2353
 
  • S.M. Gibson, A. Arteche, A. Bosco
    Royal Holloway, University of London, Surrey, United Kingdom
  • S.E. Bashforth, A. Bosco, S.M. Gibson
    JAI, Egham, Surrey, United Kingdom
  • M. Krupa, T. Lefèvre
    CERN, Geneva, Switzerland
 
  Funding: We acknowledge funding by UK STFC grant ST/N001583/1, JAI at Royal Holloway University of London and CERN
A prototype Electro-Optic Beam Position Monitor has been installed for tests* in the CERN SPS to develop the concept for high-bandwidth (6-12GHz) monitoring of crabbed-bunch rotation and intra-bunch instabilities at the High Luminosity LHC**. The technique relies on the ultrafast response of birefringent MgO:LiNO3 crystals to optically measure the intra-bunch transverse displacement of a passing relativistic bunch. This paper reports on recent developments, including a new interferometric electro-optic pick-up that was installed in the CERN SPS in September 2017; in first beam tests with nominal bunch charge, a corresponding interferometric signal has been observed. The interferometric arrangement has the advantages of being sensitive to the strongest polarisation coefficient of the crystal, and the phase offset of the interferometer is controllable by frequency scanning of the laser, which enables rapid optimisation of the working point. Novel concepts and bench tests for enhancements to the pick-up design are reviewed, together with prospects for sensitivity during the first crab-cavity beam tests at the CERN SPS in 2018.
* A. Arteche et al "First beam tests at the CERN SPS of an electro-optic beam position monitor for the HL-LHC" TUPCF23, IBIC 2017.
** HL-LHC TDR v0.1 doi.org/10.23731/CYRM-2017-004
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL073  
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WEPAL074 Commissioning of the Operational Laser Emittance Monitors for LINAC4 at CERN electron, detector, emittance, linac 2357
 
  • T. Hofmann, G.E. Boorman, A. Bosco, S.M. Gibson
    Royal Holloway, University of London, Surrey, United Kingdom
  • F. Roncarolo
    CERN, Geneva, Switzerland
 
  A laser-based emittance monitor has been developed to non-invasively measure the transverse emittance of the LINAC4 H beam at its top energy of 160MeV. After testing several sub-systems of the instrument during linac commissioning at intermediate energies, two instruments are now permanently installed. These instruments use a pulsed laser beam delivered to the accelerator tunnel by optical fibres before final focusing onto the H beam. The photons in the laser pulse detach electrons from the H ions, which can then be deflected into an electron multiplier. In addition, the resulting neutral H0 atoms can be separated from the main beam by a dipole magnet before being recorded by downstream diamond strip-detectors. By scanning the laser in the horizontal and vertical plane the beam profiles are obtained from the electron signals and the emittance can be reconstructed by the H0 profiles at the diamond detectors. This paper describes the final system layout that consists of two independent instruments, each measuring profile and emittance of the H beam in the horizontal and vertical plane and discusses the preliminary commissioning results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL074  
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WEPMF010 Laser Treatment of Niobium Surface for SRF Aplications cavity, niobium, experiment, electron 2387
 
  • V. Porshyn, D. Lützenkirchen-Hecht, P. Serbun
    Bergische Universität Wuppertal, Wuppertal, Germany
  • H. Bürger, S. Soykarci
    University of Wuppertal, Wuppertal, Germany
 
  Funding: The research was funded by the German Federal Ministry of Education and Research (BMBF) under project number 05H15PXRB1.
We report on a laser surface treatment of high purity niobium (110) single crystals. Typical surface defects like scratches, pits, sharp rims and holes were eliminated by a focused pulsed ns-laser beam. A laser fluence of about 0.68 J/cm2 and 40 - 80 pulses per spot were required to induce well detectable surface modifications. The remelted surface was sufficiently smooth, but exhibited also a number of wave structures. Thus, the surface roughness slightly increased with increasing number of pulses. Finally, boiling traces and µm-deep ablation were observed and studied as well. Local field electron emission measurements showed no emission up to 700 MV/m from a moderate remelted area below the boiling point.
 
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WEPMF056 Cs2Te Photocathode Lifetime at Flash and European XFEL cathode, FEL, gun, operation 2496
 
  • S. Lederer, S. Schreiber
    DESY, Hamburg, Germany
 
  The photo-injectors of FLASH and the European XFEL at DESY (Hamburg, Germany) use Cs2Te photocathodes. In this contribution we give an update on the lifetime and quantum efficiency of the cathodes operated in both facilities. Cathode #680.1 was operated at the European XFEL from the injector commissioning to the first user run for over 700 days. At FLASH cathode #73.3 has been operated with a record of more than 1000 days.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF056  
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WEPMF067 A High Gradient Solution for Increasing the Energy of the FERMI Linac linac, FEL, electron, wakefield 2525
 
  • C. Serpico, I. Cudin, S. Di Mitri, N. Shafqat, M. Svandrlik
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • M. Bopp, R. Zennaro
    PSI, Villigen PSI, Switzerland
 
  FERMI is the seeded Free Electron Laser (FEL) user facility at Elettra laboratory in Trieste, operating in the VUV to soft X-rays spectral range. In order to extend the FEL spectral range to shorter wavelengths, a feasibility study for increasing the Linac energy from 1.5 GeV to 1.8 GeV is actually going on. The design of new S-band accelerating structures, intended to replace the present Backward Travelling Wave sections, is presented. Such design is tailored for high gradient operation, low breakdown rates and low wakefield contribution. In this paper, we will also present the first, short prototype that has been built in collaboration with Paul Scherrer Institute (PSI).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF067  
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WEPMF079 Experimental Modal Analysis of Lightweight Structures used in Particle Detectors: Optical non-contact Method experiment, detector, operation, GUI 2565
 
  • M. Guinchard, M. Angeletti, F.B. Boyer, A. Catinaccio, C.G. Gargiulo, L.L. Lacny, E.L. Laudi, L.S. Scislo
    CERN, Geneva, Switzerland
 
  CERN's specialized structures such as particle detectors are built to have high rigidity and low weight, which comes at a cost of their high fragility. Shock and vibration issues are a key element for their successful transport, handling operations around the CERN infra-structure, as well as for their operation underground. The experimental modal analysis measurement technique is performed to validate the Finite Element Analysis in the case of complex structures (with cables and substructure coupling). In the case of lightweight structures, standard contact measurements based on accelerometers are not possible due to the high mass ratio between the accelerometers and the structure itself. In such a case, the vibration of the structure can be calculated based on the Doppler shift of the laser beam reflected off the vibrating surface. This paper details the functioning and application of an advanced laser-scanning vibrometry system, which utilizes the fore-mentioned non-contact method. The results of the Experimental Modal Analysis of selected lightweight structure using this instrument is also presented and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF079  
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WEPMG005 First Beam Test of Laser Engineered Surface Structures (LESS) at Cryogenic Temperature in CERN SPS Accelerator electron, vacuum, cryogenics, multipactoring 2616
 
  • R. Salemme, V. Baglin, S. Calatroni, P. Chiggiato, B. Di Girolamo, E. Garcia-Tabares Valdivieso, B. Jenninger, L. Prever-Loiri, M. Sitko
    CERN, Geneva, Switzerland
  • A. Abdolvand, S. Wackerow
    University of Dundee, Nethergate, Dundee, Scotland, United Kingdom
  • R. Salemme
    ITER Organization, St. Paul lez Durance, France
 
  Electron cloud mitigation is an essential requirement for accelerators of positive particles with high intensity beams to guarantee beam stability and limited heat load in cryogenic systems. Laser Engineered Surface Structures (LESS) are being considered, within the High Luminosity upgrade of the LHC collider at CERN (HL-LHC), as an option to reduce the Secondary Electron Yield (SEY) of the surfaces facing the beam, thus suppressing the elec-tron cloud phenomenon. As part of this study, a 2.2 m long Beam Screen (BS) with LESS has been tested at cryogenic temperature in the COLD bore EXperiment (COLDEX) facility in the SPS accelerator at CERN. In this paper, we describe the manufacturing procedure of the beam screen, the employed laser treatment technique and discuss our first observations in COLDEX confirming electron cloud suppression.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMG005  
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WEPML060 Yb/Nd Doped Hybrid Solid Laser of RF Gun and Beam Commissioning for Phase-II of SuperKEKB gun, injection, electron, MMI 2836
 
  • R. Zhang, T. Natsui, Y. Ogawa, M. Yoshida, X. Zhou
    KEK, Ibaraki, Japan
 
  For SuperKEKB project schedule of the phase-II, low emittance 1 nC electron beams were required with good stability and reliability at end of the linac. In the injector linac, several instruments have been installed. An Nd/Yb hybrid laser system is development with two beam lines light source. The both side of quasi-traveling wave side coupled cavity S-band RF gun were injected by the two sub μJ UV picosecond laser pulses at same times. And beam commissioning with the RF gun is in progress.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML060  
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THXGBD2 Overview of Undulator Concepts for Attosecond Single-Cycle Light electron, undulator, FEL, bunching 2878
 
  • A. Mak, V.A. Goryashko, P.M. Salen, G. K. Shamuilov
    Uppsala University, Uppsala, Sweden
  • D.J. Dunning, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • D.J. Dunning, B.W.J. MᶜNeil, N. Thompson
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • J. Hebling, Z. Tibai, Gy. Tóth
    University of Pecs, Pécs, Hungary
  • Y. Kida, T. Tanaka
    RIKEN SPring-8 Center, Hyogo, Japan
  • B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
 
  Funding: Swedish Research Council (VR, 2016-04593); Stockholm-Uppsala Centre for Free-Electron Laser Research; C. F. Liljewalchs stipendiestiftelse.
The production of intense attosecond light pulses is an active area in accelerator research, motivated by the stringent demands of attosecond science: (i) short pulse duration for resolving the fast dynamics of electrons in atoms and molecules; (ii) high photon flux for probing and controlling such dynamics with high precision. While the free-electron laser (FEL) can deliver the highest brilliance amongst laboratory x-ray sources today, the pulse duration is typically 10-100 femtoseconds. A major obstacle to attaining attosecond duration is that the number of optical cycles increases with every undulator period. Hence, an FEL pulse typically contains tens or hundreds of cycles. In recent years, several novel concepts have been proposed to shift this paradigm, providing the basis for single-cycle pulses and paving the way towards high-brilliance attosecond light sources. This article gives an overview of these concepts.
 
slides icon Slides THXGBD2 [1.762 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THXGBD2  
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THPAF033 Degradation of Electron Beam Quality for a Compact Laser-Based FEL electron, FEL, emittance, space-charge 3029
 
  • A.Y. Molodozhentsev, L. Pribyl
    Czech Republic Academy of Sciences, Institute of Physics, Prague, Czech Republic
  • K.O. Kruchinin
    ELI-BEAMS, Prague, Czech Republic
 
  Laser wake field acceleration (LWFA) mechanism allows to produce extremely short electron bunches of a few fs length with the energy up to a few GeV in extremely compact geometries providing unique electron beam parameters, in particular, transverse beam emittance (order of 1pi mm mrad), extremely short bunch length and high beam charge (up to 100pC) . This novel acceleration method therefore opens a new way to develop compact 'laser-based' FELs. In the frame of this report we analyze effects, which lead to degradation of an electron beam quality. The chromatic and collective effects are analyzed for a compact dedicated electron beam line to transport the electron beam to an undulator. In addition, the SASE FEL performance has been discussed taking into consideration the degradation of the electron beam quality.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF033  
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THPAK058 Planned Detection and Amplification of Infared Synchrotron Radiation for Electron-Beam Diagnostics and Manipulations radiation, experiment, synchrotron, synchrotron-radiation 3358
 
  • M.B. Andorf, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
 
  Amplification of beam-induced radiation (e.g. synchrotron or undulator radiation) is a necessary component of optical stochastic cooling of hadrons or heavy ions. We discuss a proposal to measure and amplify synchrotron radiation from a bending magnet of the Advanced Photon Source. The measurements will be in the short-wavelength infrared region (SWIR) and amplification will be accomplished using a pumped Chromium:Zinc Selenide (Cr:ZnSe) crystal with maximum gain at λ≅ 2.2~μm.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK058  
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THPAK060 Transverse-to-Longitudinal Photocathode Distribution Imaging quadrupole, electron, cathode, experiment 3361
 
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • W. Gai, G. Ha, J.G. Power, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • G. Ha
    PAL, Pohang, Republic of Korea
  • P. Piot
    Fermilab, Batavia, Illinois, USA
  • G. Qiang
    TUB, Beijing, People's Republic of China
 
  In this paper, we present a tunable picosecond-scale bunch train generation technique combining a microlens array (MLA) transverse laser shaper and a transverse-to-longitudinal emittance exchange (EEX) beamline. The modulated beamlet array is formed at the photocathode with the MLA setup. The resulting patterned electron beam is accelerated to 50 MeV and transported to the entrance of the EEX setup. A quadrupole channel is used to adjust the transverse spacing of the beamlet array upstream of the EEX, thereby enabling the generation of a bunch train with tunable separation downstream of the EEX beamline. Additionally, the MLA is mounted on a rotation stage which provides additional flexibility to produce high-frequency beam density modulation downstream of the EEX. Experimental results obtained at the Argonne Wakefield Accelerator (AWA) facility are presented and compared with numerical simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK060  
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THPAK063 Electron Beam Pattern Rotation as a Method of Tunable Bunch Train Generation lattice, electron, HOM, experiment 3372
 
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
 
  Transversely modulated electron beams can be formed in photo injectors via microlens array (MLA) UV laser shaping technique. Micro lenses can be arranged in polygonal lattices, with resulting transverse electron beam modulation mimicking the lenses pattern. Conventionally, square MLAs are used for UV laser beam shaping, and generated electron beam patterns form square beamlet arrays. The MLA setup can be placed on a rotational mount, thereby rotating electron beam distribution. In combination with transverse-to-longitudinal emittance exchange beam line, it allows to vary beamlets horizontal projection and tune electron bunch train. In this paper, we extend the technique to the case of different MLA lattice arrangements and explore the benefits of its rotational symmetries.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK063  
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THPAK065 Application of Transverse-to-Longitudinal Phase-Space-Exchanged Beam Produced from a Nano-Structure Photocathode to a Soft X-Ray Free-Electron Laser cathode, acceleration, simulation, quadrupole 3379
 
  • A. Lueangaramwong, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • G. Andonian
    RadiaBeam, Santa Monica, California, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
 
  Nano-structured cathodes can form transversely modulated beams which can be subsequently converted to temporally modulated beam via a transverse-to-longitudinal phase space-exchanging beamline. We demonstrate via numerical simulation the generation of transversely modulated beam at the nm scale and investigate the corresponding enhancement in a soft-X-ray SASE free-electron laser. Our study is supported by start-to-end simulation combining WARP, IMPACT-T and GENESIS(FEL process) and focuses on the optimization of the beamline to preserve initial modulation at the nanometer level. We also discuss the scaling of the concept to shorter-wavelengths.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK065  
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THPAK074 Beam Manipulation Using Self-Induced Fields in the SwissFEL Injector wakefield, FEL, electron, experiment 3401
 
  • S. Bettoni, P. Craievich, R. Ganter, P. Heimgartner, H. Jöhri, F. Marcellini, S. Reiche
    PSI, Villigen PSI, Switzerland
 
  Several possibilities of manipulating the electron beam using sources of wakefield are being explored. Wakefield have been successfully used to remove or enhance the energy chirp residual from the magnetic compression to control the free electron laser bandwidth (dechirper), to linearize the compressed beam (linearizer), to generate more bunches to produce two color mode, and to perform experiments of wakefield acceleration. At the SwissFEL injector we plan to install 2 m long system to accommodate sources of wakefield with different periodicities, each of them associated with one of the discussed beam manipulation. In this paper we summarize the design and the characterization of the system and the planned activities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK074  
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THPAK094 High Acceptance Beamline for the Capture of a Laser Wakefield Accelerated Beam quadrupole, plasma, focusing, permanent-magnet 3456
 
  • B.D. Muratori, J.K. Jones
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • K.A. Dewhurst
    University of Manchester, Manchester, United Kingdom
  • K.A. Dewhurst, J.K. Jones, H.L. Owen
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • H.L. Owen
    UMAN, Manchester, United Kingdom
 
  Laser wakefield acceleration, together with other types of novel acceleration techniques, has seen considerable progress of late. Together with this progress comes a question, which has only recently started to be addressed, of how to transport and utilise such beams. This is a challenge because of the high initial divergence of these beams. There are several approaches to this problem and we concentrate on one in this paper and look at the implications of it in some detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK094  
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THPAK154 Beam Parameter Optimization for UEM Facility with Photo-Emission S-band RF Gun electron, gun, space-charge, emittance 3610
 
  • H.R. Lee, P. Buaphad, Y. Joo
    University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
  • S.C. Cha, Y. Kim
    KAERI, Daejon, Republic of Korea
  • B.L. Cho
    KRISS, Daejeon, Republic of Korea
  • H. Suk
    GIST, Gwangju, Republic of Korea
 
  Ultrafast Electron Microscopy (UEM) can provide snapshot images of a dynamic process in samples with an ultrafast time resolution, which is shorter than picosecond. The Future Accelerator R&D Team at KAERI has been preparing a UEM facility with a photo-emission S-band (= 2856 MHz) RF gun by collaborating with GIST and KRISS. To achieve a higher spatial resolution as well as a higher time resolution, the transverse beam emittance, beam divergence, and energy spread should be smaller, and the bunch length should be shorter. Beam dynamics simulations with ASTRA code is used to optimize those beam parameters in the RF gun. In this paper, we describe ASTRA optimizations of the S-band RF gun to achieve high spatial-temporal resolutions for the UEM facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK154  
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THPAL024 A Simple Variable Focus Lens for Field Emitter Cathodes cathode, emittance, focusing, simulation 3677
 
  • R.L. Fleming, H.L. Andrews, K. Bishofberger, D. Kim, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Los Alamos National Laboratory LDRD Program
We present the design for a simple, variable-focus solenoidal lens with integrated emittance filtering. The design was developed as a first-iteration injection optics solution for transport of a beam from a field-emitter cathode into a dielectric laser accelerator structure. The design is easy to fabricate and, while based on permanent magnets, can readily be modified to allow for remote control of the focal length. The emittance is controlled via selection of collimating irises. The focal length can be changed by altering the spacing between two permanent ring magnets. Results from fabrication and initial testing will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL024  
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THPAL064 Burst-Mode UV Enhancement Cavity for Laser-Assisted Hydrogen Ion Beam Stripping at SNS cavity, resonance, experiment, controls 3799
 
  • A. Rakhman, Y. Liu
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This work has been supported in part by U.S. DOE grant DE-FG02-13ER41967. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
Recent success of laser-assisted charge exchange for 10 µs duration Hydrogen ion beams at SNS motivates laser development necessary for efficient stripping of 1.0 ms duration beam at full duty cycle. To overcome the laser power challenge, the interaction point was chosen inside an optical cavity. A doubly-resonant enhancement cavity and a novel locking technique have been developed, and a coherent enhancement of 402.5 MHz, 50 ps, 1.05 MW peak power ultraviolet (355 nm) laser pulses operating at 10-μs/10-Hz burst mode has been demonstrated. This will enable 1.0 ms duration laser macropulses at 60 Hz to be stored inside such a cavity to achieve efficient stripping at SNS.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL064  
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THPAL071 Preliminary Emittance Measurement of Laser Driven Proton Beam Employing a Quadruple Triplet Magnet proton, emittance, experiment, quadrupole 3818
 
  • Wu,M.J. Wu, Y.X. Geng, Q. Liao, C. Lin, H.Y. Lu, Y.R. Lu, W.J. Ma, Y.R. Shou, X. Xu, X.Q. Yan, Y.Y. Zhao, J.G. Zhu, K. Zhu
    PKU, Beijing, People's Republic of China
 
  The Compact Laser Plasma Accelerator (CLAPA) has been built recently at Peking University, which composed of a 200TW laser acceleration platform and a beam line system. Proton with energy spread of <1%, up to 10 pC charge and different energies below 10 MeV have been produced and transported to the irradiation platform. Emittance is a critical parameter for beam transportation. The preliminary emittance measurement has been per-formed for CLAPA's proton beams using the quadrupole scan technique (QST). In the experiment, the focal spot size of the proton beam was changed by scanning the current of a quadrupole triplet magnet. The result shows that the normalized emittance is smaller than 0.01 mm·mrad for 5 MeV laser driven protons, which is on the same level of the previously reported work.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL071  
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THPAL095 Metal Photocathodes Preparation for Compact Linear Accelerator at Daresbury Laboratory plasma, cathode, electron, gun 3865
 
  • A.N. Hannah, J.A. Conlon, L.B. Jones, B.L. Militsyn, T.C.Q. Noakes, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • V. R. Dhanak
    The University of Liverpool, Liverpool, United Kingdom
  • L.B. Jones, B.L. Militsyn
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • S. Lederer
    DESY Zeuthen, Zeuthen, Germany
  • S. Lederer
    DESY, Hamburg, Germany
 
  The photoinjector of the CLARA FEL test facility Front End at Daresbury Laboratory is based on a S-band 10 Hz photocathode RF-gun operating with a copper photocath-ode which is driven by the third harmonic of a Ti:Sapphire laser (266 nm). The main aim of this study was to establish a procedure to prepare the Cu surface prior to installation so a Quantum Efficiency (QE) of 10-5 or higher can be achieved at laser power density below the ablation threshold of copper. The best results have been obtained by ex-situ chemical cleaning. This removed the surface oxide layer whilst at the same time producing a surface buffer layer. This inhibited the regrowth of native oxide for up to a week when exposed to normal ambient atmospheric conditions. With either chemical cleaning or Ar plasma cleaning after heating the sample in-situ to 150 °C for 90 minutes or 250 °C for 40 hours, almost all of the surface oxide was removed. For these surfaces a QE of 4.10-5 or better was measured. Oxygen plasma cleaning at 100% and 20% power produced CuO layer with surface carbon contaminant to 3 atomic %, however in-situ thermal cycling resulted in at best a QE of 3·10-6.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL095  
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THPAL133 LASE Surfaces for Mitigation of Electron Cloud in Accelerators electron, vacuum, cavity, experiment 3958
 
  • B.S. Sian
    UMAN, Manchester, United Kingdom
  • O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Vacuum chamber surface characteristics such as the photon and secondary electron yields (PEY and SEY) are critical parameters in the formation of an electron cloud, a serious problem that limits the performance of proton and positron accelerators. A few years ago it was discovered by the Vacuum Solutions Group at Daresbury laboratory that Laser Ablation Surface Engineering (LASE) could provide surfaces with SEY<1 [1,2]. The LASE surfaces are considered as a baseline solution for electron cloud miti-gation in the Future Circular Collider (FCC). However, these surfaces are undergoing further optimisation for the FCC application. While keeping SEY<1 the surfaces should meet the following criteria: Low outgassing, Low particulate generation and low surface resistance. In this paper we will report a number of new surfaces created using the LASE technique with different laser parameters (wavelength, scan speed, pitch, repetition rate, power, and pulse length) and their effect on the SEY, surface re-sistance and vacuum properties, etc  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL133  
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THPMF011 Femtosecond Laser Ablation for Manufacturing of X-ray Lenses and Phase Corrector Plates optics, photon, storage-ring, experiment 4057
 
  • S.P. Antipov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • L. Assoufid, W.C. Grizolli, J. Qian, X. Shi
    ANL, Argonne, Illinois, USA
 
  Funding: DOE SBIR
The next generation light sources such as diffraction limited storage rings and high repetition rate free electron lasers (FELs) will generate X-ray beams with significantly increased peak and average brilliance. These future facilities will require X-ray optical components capable of handling large instantaneous and average power densities while tailoring the properties of the X-ray beams for a variety of scientific experiments. In this paper we report on research and development of a single crystal diamond compound refractive lens. Diamond lenses presented here are fabricated by fs-laser cutting and subsequent polishing. Grating interferometry measurement data of these lenses had been performed at the Advanced Photon Source (Argonne). Besides the lenses, we fabricated and tested several phase correction plates, a refractive elements designed to correct for cumulative X-ray beam aberrations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF011  
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THPMF028 Coherent Stacking Scheme for Inverse-Compton Scattering at MHz Repetition Rates cavity, simulation, coupling, feedback 4103
 
  • P. Piot, D. Mihalcea
    Northern Illinois University, DeKalb, Illinois, USA
  • T.J. Campese, A.Y. Murokh
    RadiaBeam Systems, Santa Monica, California, USA
  • D. Mihalcea, P. Piot, J. Ruan
    Fermilab, Batavia, Illinois, USA
 
  Funding: Work sponsored by the DNDO award 2015-DN-077-ARI094 to Northern Illinois University and US DOE contract DE-AC02-07CH11359 to Fermilab.
An experiment to produce 1-MeV gamma rays via Compton back-scattering of infrared photons on 250-MeV electron bunches is currently in preparation at the Fermilab Accelerator Science & Technology (FAST) facility. To increase the gamma-ray flux the energy of the infrared laser pulses are planned to be amplified within the interaction region using a resonant cavity. This passive amplifier composed of a Fabry-Perot cavity will allow the laser pulse bunches to coherently and constructively stack. Our estimates, based on theoretical models, show that the laser pulse energy can be increased from approximately 1-2 mJ at the exit of the last active amplifier to 5 -10 mJ at the interaction point when the laser repetition rate is set at the nominal value of 3 MHz. This paper details the cavity design option(s) and associated wave-optic simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF028  
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THPMF029 Novel MCP-Based Electron Source Studies electron, gun, cathode, controls 4107
 
  • V.D. Shiltsev, G. Stancari
    Fermilab, Batavia, Illinois, USA
  • M.J. Haughey
    Edinburgh University, Edinburgh, United Kingdom
 
  Microchannel plates were recently proposed as cathodes for electron guns, as part of a novel electron lens design to be tested in the IOTA facility at FNAL. We experimentally assessed the suitability of microchannel plate technology in this design and studied the microchannel plate based photomultiplier (MCP-PMT) system using different sources of light pulses. Here we present the results of the nanosecond time response tests and the maximum current density tests as well as the dependency on the magnetic field strength. Several ideas how to proceed beyond O(100 mA/cm2) density observed in the first tests.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF029  
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THPMF039 Study of Magnesium Photocathodes for Superconducting RF Photoinjectors gun, cathode, SRF, cavity 4142
 
  • R. Xiang, A. Arnold, P.N. Lu, P. Murcek, J. Teichert, H. Vennekate
    HZDR, Dresden, Germany
 
  Funding: The work is supported by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1.
The superconducting RF photoinjector (SRF Gun II) has successfully served for the ELBE user facility at HZDR. Nevertheless, the quality of photocathodes is one of the most critical issues in improving the stability and reliability for its application. Magnesium has a comparably low work function (3.6 eV) and shows a quantum efficiency up to 0.3% after laser cleaning. However, the present cleaning process with a high intensity laser beam is time consuming and produces unwanted surface roughness, which leads to a higher thermal emittance. Thermal treatment and Excimer laser cleaning for Mg cathodes are investigated as alternative methods. In this work, the new cleaning procedures are tested and optimized, and the quantum efficiency of Mg samples with different microstructure, composition and suppliers are compared.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF039  
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THPMF048 Bunch Length Measurements Using CTR at the AWA with Comparison to Simulation experiment, simulation, gun, electron 4166
 
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  • S.P. Antipov
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • A. Halavanau, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • P. Piot
    Fermilab, Batavia, Illinois, USA
  • J.G. Power, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  Funding: This work is funded by the DOE Office of Science, grant no. DE-SC0015479, and contract No. DE-AC02- 06CH11357.
In this paper we present electron bunch length measurements at the Argonne Wakefield Accelerator (AWA) photoinjector facility. The AWA accelerator has a large dynamic charge density range, with electron beam charge varying between 0.1 nC - 100 nC, and laser spot size diameter at the cathode between 0.1 mm - 18 mm. The bunch length measurements were taken at different charge densities using a metallic screen and a Martin-Puplett interferometer to perform autocorrelation scans of the corresponding coherent transition radiation (CTR). A liquid helium-cooled 4K bolometer was used to register the interferometer signal. The experimental results are compared with Impact-T and OPAL-T numerical simulations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF048  
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THPMF049 Photoinjector Optimization Studies at the AWA simulation, emittance, experiment, gun 4169
 
  • N.R. Neveu
    IIT, Chicago, Illinois, USA
  • J. Larson, J.G. Power
    ANL, Argonne, Illinois, USA
  • L.K. Spentzouris
    Illinois Institute of Technology, Chicago, Illinois, USA
 
  Funding: This work is funded by the DOE Office of Science, grant no. DE-SC0015479, and contract No. DE-AC02- 06CH11357.
With a variable charge range of 0.1 nC - 100 nC, the Argonne Wakefield Accelerator facility (AWA) has a unique and dynamic set of operating parameters. Adjustment of the optics and occasionally the rf phases is required each time the bunch charge is changed. Presently, these adjustments are done by the operator during each experiment. This is time consuming and inefficient, more so at high charge and for complex experimental set ups. In an attempt to reduce the amount of time spent adjusting parameters by hand, several optimization methods in simulation are being explored. This includes using the well-known Genetic Algorithm (NSGA-II), incorporated into OPAL-T. We have also investigated a model-based method and novel structure based algorithms developed at ANL. Ongoing efforts include using these optimization methods to improve operations at the AWA. Simulation results will be compared to measured beam parameters at the AWA, and one optimization method will be selected for use in guiding operations going forward.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF049  
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THPMF050 High-Efficient XFELO Based on Optical Resonator with Self-Modulated Q-Factor undulator, FEL, coupling, electron 4172
 
  • S.V. Kuzikov, A.V. Savilov, A.A. Vikharev
    IAP/RAS, Nizhny Novgorod, Russia
  • S.P. Antipov, S.V. Kuzikov
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  In this paper we describe an efficient XFELO having a new non-stationary out-coupling scheme. It consists of two undulator sections placed inside optical cavity. The first section is a conventional uniform undulator and the second one is a tapered undulator. At start time point X-ray radiation is mostly produced by the uniform section. Mirrors of XFELO's optical resonator are designed so that diffraction Q-factor reaches the highest value, i.e losses are near zero. As X-ray power increases the tapered undulator begins to contribute more to radiation power. However a portion of that power misses mirrors of the optical cavity, because those are tuned to confine radiation produced by the first undulator. This process establishes a steady state operation of the XFELO.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF050  
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THPMF056 Optimisation Study of the Fabry-Pérot Optical Cavity for the MARIX/BRIXS Compton X-Ray Source cavity, electron, gun, photon 4192
 
  • I. Drebot, A. Bacci, F. Broggi, S. Cialdi, C. Curatolo, D. Giannotti, D. Giove, A.R. Rossi, L. Serafini, M. Statera, V. Torri
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  • A. Bosotti, P. Michelato, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • R. Calandrino, A. Delvecchio
    HSP, Milan, Italy
  • P. Cardarelli, M. Gambaccini, G. Paternò, A. Taibi
    INFN-Ferrara, Ferrara, Italy
  • A. Esposito, L. Faillace, A. Gallo, C. Vaccarezza
    INFN/LNF, Frascati (Roma), Italy
  • G. Galzerano, E. Puppin, A. Tagliaferri
    Politecnico/Milano, Milano, Italy
  • G. Mettivier, P. Russo
    UniNa, Napoli, Italy
  • V. Petrillo, F. Prelz, M. Rossetti Conti
    Universita' degli Studi di Milano & INFN, Milano, Italy
  • M. Placidi, G. Turchetti
    Bologna University, Bologna, Italy
  • A. Sarno
    INFN-Napoli, Napoli, Italy
 
  We present the study of the optimization of the optical cavity parameters, in order to maximise the flux of scattered photons in the Compton scattering process. In the optimisation, we compensate the losses of the photon number due to the elliptical shape of the laser pulse in optical cavity with a high focusing electron beam.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF056  
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THPMF057 Multi Colour X-Gamma Ray Inverse Compton Back-Scattering Source electron, radiation, photon, cavity 4196
 
  • I. Drebot, S. Cialdi, D. Giannotti, L. Serafini
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  • R. Calandrino
    HSP, Milan, Italy
  • P. Cardarelli, M. Gambaccini, G. Paternò, A. Taibi
    INFN-Ferrara, Ferrara, Italy
  • G. Galzerano
    Politecnico/Milano, Milano, Italy
  • V. Petrillo
    Universita' degli Studi di Milano & INFN, Milano, Italy
 
  We present a simple and new scheme for producing multi colour Thomson/Compton radiation with the possibility of controlling separately their polarization, based on the interaction of one single electron beam with two and more laser pulses that can come from the same laser setup or from two different lasers system and that collide with the electrons at different angle inside one optical cavity. One of the most interesting cases for medical applications is to provide two X-ray pulses across the iodine K-edge at 33.2 keV. The iodine is used as contrast medium in various imaging techniques and the availability of two spectral lines accross the K-edge allows one to produce subtraction images with a great increase in accuracy.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF057  
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THPMF068 Commissioning Status of FLUTE gun, electron, experiment, MMI 4229
 
  • A. Malygin, A. Bernhard, E. Bründermann, A. Böhm, S. Funkner, S. Marsching, W. Mexner, A. Mochihashi, A.-S. Müller, M.J. Nasse, G. Niehues, R. Ruprecht, T. Schmelzer, M. Schuh, N.J. Smale, P. Wesolowski, M. Yan
    KIT, Karlsruhe, Germany
  • I. Križnar
    Cosylab, Ljubljana, Slovenia
  • M. Schwarz
    CERN, Geneva, Switzerland
 
  FLUTE (Ferninfrarot Linac- Und Test-Experiment) will be a new compact versatile linear accelerator at the KIT. Its primary goal is to serve as a platform for a variety of accelerator studies as well as to generate strong ultra-short THz pulses for photon science. The phase I of the project, which includes the RF photo injector providing electrons at beam energy of 7 MeV and a corresponding diagnostics section, is currently being commissioned. In this contribution, we report on the latest progress of the commissioning phase. The status of the gun conditioning will be given, followed by an overview of the RF system and the laser system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF068  
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THPMF071 Design of a Very Large Acceptance Compact Storage Ring lattice, storage-ring, electron, sextupole 4239
 
  • A.I. Papash, E. Bründermann, A.-S. Müller, R. Ruprecht, M. Schuh
    KIT, Eggenstein-Leopoldshafen, Germany
 
  Design of a very large acceptance compact storage ring is underway at the Institute for Beam Physics and Technology of the Karlsruhe Institute of Technology (Germany). Combination of a compact storage ring and a laser wake-field accelerator (LWFA) might be the basis for future compact light sources and advancing user facilities. Meanwhile the post-LWFA beam is not fitted for storage and accumulation in conventional storage rings. New generation rings with adapted features are required. Different geometries and lattices of a ring operating between 50 to 500 MeV energy range were investigated. The model suitable to store the post-LWFA beam with a wide momentum spread (1% to 2%) and ultra-short electron bunches of fs range was chosen as basis for further detailed studies. The DBA-FDF lattice with relaxed settings, split elements and high order optics of tolerable strength allows improving the dynamic aperture up to 20 mm. The momentum acceptance of the compact lattice exceeds 8% while dispersion is limited. The physical program includes turn-by-turn phase compression of a beam, crab cavities, dedicated alpha optics mode of operation, non-linear insertion devices etc.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF071  
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THPMF072 Implementation of Ultra-Low Frequency Non-Linear Raman Spectroscopy with the Gun Laser at FLUTE experiment, scattering, gun, optics 4242
 
  • S. Funkner, E. Bründermann, A.-S. Müller, M.J. Nasse, G. Niehues, T. Schmelzer, J.L. Steinmann, M. Yan
    KIT, Eggenstein-Leopoldshafen, Germany
  • M. Tani
    University of Fukui, Fukui, Japan
 
  At the Karlsruhe Institute of Technology (KIT) the new compact versatile linear accelerator FLUTE is currently under commissioning. This accelerator will provide intense broadband THz pulses for spectroscopic experiments. Here, we demonstrate the implementation of a coherent Raman spectrometer using the RF gun laser of FLUTE. With our experiment, we can measure the Raman spectrum at ultra-low frequencies. The measurement principle, which was recently published, is based on coherent nonlinear excitation of the observed sample. The spectrometer consists of a stretcher and an interferometer, which can be simply built from standard optics. We will show that the accessible spectral range overlaps well with that from the THz pulses of the planned FLUTE experiment. Thus, the coherent Raman experiment can provide spectral information complementary to absorption spectral measurements using the THz radiation of FLUTE.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF072  
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THPMF074 Study of the Saturation of Radiation Energy Caused by the Space Charge Effect in a Compact THz Coherent Radiation Source electron, radiation, undulator, simulation 4245
 
  • S. Krainara, Chatani, S. Chatani, T. Kii, H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
 
  Funding: Institute of Advanced Energy, Kyoto University
To generate an intense quasi-monochromatic Terahertz Coherent Undulator Radiation (THz-CUR), a compact linac system, which employs a magnetic electron bunch compressor with a beam energy of 4.6 MeV, has been constructed at Kyoto University. The THz-CUR has suc-cessfully been generated in a frequency range from 0.16 to 0.65 THz with a bunch charge of 60 pC. The maximum micro-pulse energy of THz radiation was observed higher than 1 µJ at 0.16 THz with 160 pC. However, when a bunch charge was higher than 80 pC, the micro-pulse energy of THz radiation gradually went to the saturation and obviously at the bunch charge higher than 110 pC because of the bunch lengthening and degradation of electron beam quality due to the space charge effect. The dependence of a bunch length on a bunch charge has been studied by GPT simulation and compared with CTR and CUR experiments. The trends of the measured results from CUR and CTR are in good agreement with the GPT simulation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF074  
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THPMF076 New Simulation Programs for Partially Stripped Ions - Laser Light Collisions photon, electron, factory, FEL 4249
 
  • C. Curatolo, L. Serafini
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  • M.W. Krasny
    LPNHE, Paris, France
  • W. Placzek
    Marian Smoluchowski Institute of Physics, Jagiellonian University, Kraków, Poland
 
  We present for the first time two new indipendent Monte Carlo codes for simulating the collisions of Partially Stripped Ions with Laser light. Such collisions if realised at LHC could drive a high intensity gamma source and are the back-bone of the recent Gamma Factory proposal. The implementation aspects will be discussed and the simulation results will be compared.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF076  
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THPMF080 Physical and Chemical Roughness of Alkali-Animonide Cathodes cathode, electron, emittance, vacuum 4259
 
  • S.S. Karkare, S. Emamian, G. Gevorkyan, H.A. Padmore, A.K. Schmid
    LBNL, Berkeley, California, USA
  • I.V. Bazarov
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • A. Galdi
    Cornell University, Ithaca, New York, USA
 
  Over the last decade, alkali-antimonides have been investigated as high QE cathodes in green light and more recently as ultra-low intrinsic emittance cathodes in near-threshold red wavelengths at cryogenic temperatures*. Nano-meter scale surface non-uniformities (physical roughness and chemical roughness or work function variations) are thought to limit the smallest possible emittance from these materials at the photoemission threshold under cryogenic conditions**. Despite this, the surfaces of alkali-antimonides have not been well characterized in terms of the surface non-uniformities. Here, we present measurements of both the physical and chemical roughness of alkali-antimonide surfaces using several surface characterization techniques like atomic force microscopy, kelvin probe force microscopy, low energy electron microscopy and near-threshold photoemission electron microscopy and show how such non-uniformities limit the intrinsic emittance.
*L. Cultrera et al Phys. Rev. ST Accel. Beams 18, 113401 (2015)
**J. Feng et al, J. of Appl. Phys. 121, 044904 (2017)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF080  
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THPMF082 Suppression of Microbunching Instability Using a Quadrupole Inserted Chicane in Free-Electron-Laser Linacs bunching, linac, electron, FEL 4267
 
  • B. Li, J. Qiang
    LBNL, Berkeley, California, USA
 
  The microbunching instability (MBI) driven by beam collective effects in a linear accelerator of a free-electron laser (FEL) facility can significantly degrade the electron beam quality and FEL performance. A method exploited longitudinal mixing derived from the natural transverse spread of the beam was proposed several years ago using two dipoles to suppress the instability. In this paper, instead of using bending magnets to introduce the transverse-to-longitudinal coupling, which will lead to an inconvenient deflection of the downstream beam line, we propose a scheme using a quadrupole inserted chicane to introduce the longitudinal mixing inside the accelerator transport system to suppress this instability. And we finally eliminate the transverse-to-longitudinal coupling after the dogleg section.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF082  
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THPMF083 Dynamic Simulation for Low Energy Compton Scattering Gamma-Ray Storage Ring electron, scattering, emittance, storage-ring 4271
 
  • Z. Pan, J.M. Byrd, C. Sun
    LBNL, Berkeley, USA
  • H. Hao, Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
  • W.-H. Huang, C.-X. Tang
    TUB, Beijing, People's Republic of China
 
  We have designed a dedicated low-energy electron storage ring to generate gamma-rays based on Compton scattering technique. The natural emittance of the ring is 3.4 nm at 500 MeV beam energy and the ring circumference is about 59 m. The resulting maximum gamma-ray photon energy is about 4 MeV by interacting with ~1 um laser. Due to the large energy loss associated with the gamma-ray photon emission, the electron beam dynamics are greatly affected. We have simulated the whole physics process including Compton scattering, radiation damping and quantum excitation and find that the equilibrium energy spread may be increased by one orders of magnitude depending on the laser parameters. We have studied the dependence of the equilibrium state on the laser intensity and wavelength, and the electron parameters based on our candidate ring lattice.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF083  
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THPMF086 Reliability Improvement on Wiggler Period Averaging Approximation wiggler, FEL, simulation, plasma 4281
 
  • K. Hwang, J. Qiang
    LBNL, Berkeley, California, USA
 
  Funding: US Department of Energy under Contract no. DEAC02-05CH11231
As the wiggler period averaging is subject to reliability issue, many efforts on FEL codes without such approximations are made at the cost of heavier computation loads. However, efforts toward increasing the reliability of such approximation are few. In this report, we present a new capability of IMPACT code suite based on such approximation with the addition of perturbative corrections to wiggler period averaging error.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF086  
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THPMF088 R&D Activity on Alkali-Antimonied Photocathodes at INFN-Lasa cathode, gun, electron, operation 4284
 
  • D. Sertore, P. Michelato, L. Monaco
    INFN/LASA, Segrate (MI), Italy
  • C. Pagani
    Università degli Studi di Milano & INFN, Segrate, Italy
 
  Based on the long-term experience on R&D and production of cesium telluride photocathodes for the high brightness photo-injectors and the past experience on green photocathodes developed in ‘90s , we have started a new R&D activity aiming to reach a reproducible and robust recipe for green photocathodes usable in RF gun. In this paper we present and discuss the first results so far obtained on K2CsSb photoemissive films deposited on polished Mo plugs and the plan for future studies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF088  
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THPMK002 The Pre-Injector Design for the MAX IV SXL gun, cathode, emittance, linac 4297
 
  • J. Andersson, M. Kotur, D. Kumbaro, F. Lindau, E. Mansten, D. Olsson, L.K. Roslund, S. Thorin
    MAX IV Laboratory, Lund University, Lund, Sweden
 
  In this paper we present the current status of the design for the pre-injector (photo-cathode gun, solenoid and first linac) for the SXL project at MAX IV. The SXL project requires a higher repetition rate and since improved beam quality compared to what the current photo-cathode gun can operate at is needed, a new photo-cathode gun will be manufactured. We briefly describe the components of the pre-injector, followed by the design of the new photo-cathode gun. The design is similar to the old gun but with a new RF cavity using elliptical irises and racetrack profile main cell. The current parameters for the next gun to be manufactured are discussed, and some simulations and expected beam quality from the injector are shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK002  
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THPMK007 Surface Acoustic Wave Enhancement of Photocathodes simulation, electron, cathode, photon 4304
 
  • R.P. Johnson
    Muons, Inc, Illinois, USA
  • A. Afanasev, B. Dong, M. E. Zaghloul
    GWU, Washington, USA
 
  Funding: Work supported by DOE HEP STTR Grant DE-SC0017831
Numerical simulations and fabrication techniques are being used to investigate the use of surface acoustic waves to suppress electron-hole recombination on the surface of GaAs photocathodes in order to increase the quantum efficiency for polarized and unpolarized electron beam generation.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK007  
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THPMK008 Commissioning of the Storage Ring for the Kharkov Generator of X-Ray Radiation NESTOR storage-ring, electron, MMI, injection 4307
 
  • A.A. Shcherbakov, V.P. Androsov, S.V. Bazarov, V.N. Berezka, O. Bezditko, A.V. Cherkashin, A.V. Gevchuk, P. Gladkikh, S.P. Gokov, A.N. Gordienko, V.A. Grevtsev, A. Gvozd, V.E. Ivashchenko, A.A. Kalamayko, I.I. Karnaukhov, I.M. Karnaukhov, V.P. Kozin, V.P. Lyashchenko, V.S. Margin, N.I. Mocheshnikov, M. Moisieienko, A. Mytsykov, F.A. Peev, O.V. Ryezayev, V.P. Sergienko, V.O. Shpagina, N.F. Shul'ga, V. Skomorokhov, D.V. Tarasov, V.I. Trotsenko, V.V. Tsyats'ko, A.Y. Zelinsky, O.P. Zolochevskij, O.D. Zvonarjova
    NSC/KIPT, Kharkov, Ukraine
  • J.I.M. Botman
    TUE, Eindhoven, The Netherlands
 
  During 2015-2017 the X-ray source NESTOR (New Electron STOrage Ring) based on a storage ring with low beam energy and Compton scattering of intense laser beam is under commissioning at the National Science Center "Kharkov Institute of Physics and Technology Institute" (NSC KIPT). The start-up of the injector and storage ring is one of the basic task for the facility commissioning. In the paper, the results of the NESTOR X-ray source 225 MeV electron storage ring commissioning are described and further plans are discussed  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK008  
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THPMK009 Study on Improving Durability of Bialkali Photocathode for an RF-Gun with the CsBr Protective Layer cathode, gun, electron, ion-source 4310
 
  • J. Miyamatsu, H. Ono, M. Washio
    Waseda University, Tokyo, Japan
  • H. Iijima
    Tokyo University of Science, Tokyo, Japan
  • K. Sakaue
    Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
 
  At Waseda University, we have been studying for high quality electron beam generation and developing variety of application experiments using 1.6 cells photocathode RF-gun. We are using photocathode as the electron source, which can generate high-performance electron beam such as low emittance, short pulse. The performance of photocathodes is evaluated mainly in terms of Quantum Efficiency (Q.E.) and the lifetime. Cs-Te photocathode used in the RF-Gun at Waseda University is known for high Q.E. with UV light and relatively longer lifetime among semiconducting photocathodes. For increasing the charge of electron beam and simplify the laser system, we started introducing CsK2Sb photocathode in the RF-gun which has light sensitivity in UV and visible range, and high Q.E. with green light. However, CsK2Sb photocathode has a difficulty in durability and we observed that it was not enough for long-term operation in the RF-gun. Then we plan to improve lifetime and durability of CsK2Sb photocathode by coating the cathode surface with CsBr thin film. In this conference, we report the result of lifetime measurement of CsK2Sb photocathode with CsBr thin film and future prospects.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK009  
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THPMK026 Mobile Free-Electron Laser for Remote Atmospheric Survey FEL, electron, survey, free-electron-laser 4351
 
  • S. Johnson, G.A. Krafft, B. Terzić
    ODU, Norfolk, Virginia, USA
  • G.A. Krafft
    JLab, Newport News, Virginia, USA
 
  Funding: This paper is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05- 06OR23177. E.J. was supported by the Virginia Space Grant Consortium, grant number 16-589.
Reliable atmospheric surveys for carbon distributions will be essential to building an understanding of the Earth's carbon cycle and the role it plays in climate change. One of the core needs of NASA 's Active Sensing of CO2 Over Nights, Days and Seasons (ASCENDS) Mission is to advance the range and precision of current remote atmospheric survey techniques. The feasibility of using accelerator-based sources of infrared light to improve current airborne lidar systems has been explored. A literary review has been conducted to asses the needs of ASCENDS versus the current capabilities of modern atmospheric survey technology, and the parameters of a free electron laser (FEL) source were calculated for a lidar system that will meet these needs. By using the "Next Linear Collider" from the Stanford Linear Accelerator Center (SLAC), a mobile FEL-based lidar may be constructed for airborne surveillance. The calculated energy of the lidar pulse is 0.1 joule: this output is a two orders of magnitude gain over current lidar systems, so in principle, the mobile FEL will exceed the needs of ASCENDS. Further research will be required to asses other challenges to mobilizing the FEL technology.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK026  
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THPMK028 Inverse Free Electron Laser Separatrix Crossing for Energy Gain and Stability FEL, undulator, electron, free-electron-laser 4354
 
  • N.S. Sudar, P. Musumeci
    UCLA, Los Angeles, USA
  • D. Garzella
    CEA, Gif-sur-Yvette, France
 
  The laser wakefield accelerator (LWFA) has been proposed as a driver for next generation compact light sources. However, the beams produced by LWFA's typically exhibit correlated energy spread and energy jitter too large to drive the Free Electron Laser instability. We present here a novel scheme whereby using a highly non-linear strongly tapered undulator interaction directly after the LWFA we are able to trap and accelerate a large fraction of charge in the moving Inverse Free Electron Laser ponderomotive bucket. The final correlated energy spread and output energy are determined by the final bucket height and central energy of the ponderomotive bucket which are both determined by the stagnant undulator parameters, resulting in a significant decrease in the normalized energy spread (< 1%) and output energy jitter (< 1%). This interaction is treated both analytically and numerically.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK028  
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THPMK035 Generation of Isolated Zeptosecond Pulse in Gamma-Ray Free Electron Laser undulator, radiation, electron, ISOL 4375
 
  • C.H. Shim, D.E. Kim
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • Y.W. Parc
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  An X-ray pulse with zeptosecond pulse duration is an essential tool to resolve the nuclear dynamics. To make such a short pulse duration, we need to make a very wide frequency range radiation which is known from the uncertainty principle. The spectral range of an isolated zeptosecond pulse has to be of order of few keV which is called as a gamma ray. In this presentation, the generation of an isolated zeptosecond pulses in the gamma-ray free electron laser is studied by the simulation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK035  
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THPMK042 Two and Multiple Bunches at LCLS undulator, diagnostics, photon, FEL 4378
 
  • F.-J. Decker, K.L.F. Bane, R.N. Coffee, W.S. Colocho, S. Gilevich, S.H. Glenzer, A.A. Lutman, A. Miahnahri, D.F. Ratner, J.C. Sheppard, S. Vetter
    SLAC, Menlo Park, California, USA
 
  The LCLS X-Ray FEL at SLAC typically delivers one bunch at the time. Different schemes of two pulses have been developed: Two bucket, Twin bunch, split undulator, and fresh slice. Here we discuss a four bunch or even eight bunch setup, where the separation between the individual bunches is two RF buckets: 0.7 ns.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK042  
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THPMK043 Timing Stability at LCLS timing, cavity, linac, FEL 4381
 
  • F.-J. Decker, R.N. Coffee, W.S. Colocho, J.M. Glownia, K. Gumerlock, B.L. Hill, T.J. Maxwell, J. May
    SLAC, Menlo Park, California, USA
 
  The beam stability of the LCLS (Linac Coherent Light Source) has increased substantially over the years. Transversely it is a fraction of the beam size. The energy jitter was reduced from five times the energy spread to a fraction of it. Only the timing jitter is left. It got improved during the energy jitter reduction, but typically left alone. So we have five dimensions of the six-dimensional phase space covered with feedbacks and special 60-Hz jitter setups which eliminate the difference between every other pulse, but not for the general timing setup. We describe a scheme with the RF of the XTCAV, which could be used for other setups like lasers.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK043  
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THPMK045 Generation of High Power, High Intensity, Ultra Short X-Ray FEL Pulses electron, free-electron-laser, photon, emittance 4384
 
  • M.W. Guetg, Y. Ding, Z. Huang, A.A. Lutman
    SLAC, Menlo Park, California, USA
 
  X-ray Free Electron Lasers combine high pulse power, short pulse length, narrow bandwidth and a high degree of transverse coherence. Any increase in the photon pulse power, while shortening the pulse length, will further push the frontier on several key XFEL applications including single molecule imaging and novel nonlinear X-ray methods. We will present experimental results at the Linac Coherent Light Source raising its maximum power to more than 300% of the current limit, while reducing the photon pulse length to 10 fs. This was achieved by minimizing residual transverse-longitudinal centroid beam offsets and beam yaw, and by correcting the dispersion when operating over 6 kA peak current with a longitudinally shaped beam.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK045  
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THPMK046 Advanced Fresh-Slice Beam Manipulations for FEL X-Ray Applications electron, undulator, controls, free-electron-laser 4387
 
  • A.A. Lutman, Y. Ding, M.W. Guetg, Z. Huang, J. Krzywinski, J.P. MacArthur, A. Marinelli, T.J. Maxwell
    SLAC, Menlo Park, California, USA
  • C. Emma
    UCLA, Los Angeles, USA
 
  The recent development of the Fresh-slice technique granted control on which temporal slice lases in each undulator section in an X-ray Free-electron laser. Fresh-slice has been used for several experiments at the Linac Coherent Light Source for the generation of customizable high power two-color beams, and increased the performance of self-seeding schemes. As a novel development of the technique we present the demonstration of multistage self-amplified spontaneous-emission amplification schemes for the production of high-power ultra short pulses and improved control of the temporal duration of each pulse in multi-pulse schemes.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK046  
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THPMK051 Theoretical Formulation of Improved SASE FEL Based on Slippage Enhancement Scheme electron, FEL, undulator, radiation 4398
 
  • C.-Y. Tsai, J. Wu, C. Yang, G. Zhou
    SLAC, Menlo Park, California, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • G. Zhou
    IHEP, Beijing, People's Republic of China
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE- AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
A method to improve the spectral brightness of self-amplified spontaneous emission (SASE) based on slippage enhancement has been proposed*, **. The implementation is to insert a series of magnetic chicanes to introduce a path-length delay of the electron beam to the radiation beam. By correlating the electron slices of neighboring cooperation distances this can lengthen the collective interaction and thus enhance the spectral brightness. In the existing literature most studies rely on numerical simulations and there is limited work on analytical analysis. In this paper we formulate the problem of slippage enhanced SASE (SeSASE) high-gain FEL with inclusion of by-pass magnetic chicanes. The analysis takes the finite energy spread of the electron beam and the nonzero momentum compaction of the chicane into consideration. The evolution of spectral bandwidth of SeSASE is compared with that of usual SASE in theory and numerical simulations. The effects of finite beam energy spread and non-isochronisity are also quantified.
*J. Wu et al., FEL2012
**B. W. J. McNeil et al., PRL 110, 134802 (2013)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK051  
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THPMK054 Analysis of 1D FEL Sideband Instability with Inclusion of Energy Detune and Space Charge FEL, space-charge, electron, undulator 4410
 
  • C.-Y. Tsai, J. Wu, C. Yang, G. Zhou
    SLAC, Menlo Park, California, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE- AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
It has been known that free-electron laser (FEL) is capable of generating a coherent high-power radiation over a broad spectrum. Recently there is a great interest in pursuing higher peak power (for example, at terawatt level) in FEL that can enable coherent diffraction imaging and probe fundamental high-field physics. The FEL radiation power can be increased by virtue of undulator tapering. However the FEL sideband signal begins to exponentially grow in the post-saturation regime. In this paper we extend our sideband analysis* by including both the energy detune due to discrete undulator tapering and longitudinal space charge in an effective 1-D model. A dispersion relation with explicit energy detune and space charge is derived. The study is carried out semi-analytically and compared with simulations. The impact of energy detune and space charge is analyzed.
* C.-Y. Tsai et al., Analysis of the sideband instability based on a one-dimensional high-gain free electron laser model, PRAB (accepted)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK054  
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THPMK056 Effect of Transverse Radiation Defocusing in Post-Saturation Regime of High-Gain X-Ray Free-Electron Laser electron, radiation, undulator, FEL 4418
 
  • C.-Y. Tsai, J. Wu, C. Yang, G. Zhou
    SLAC, Menlo Park, California, USA
  • M. Yoon
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • G. Zhou
    IHEP, Beijing, People's Republic of China
 
  Funding: The work was supported by the US Department of Energy (DOE) under contract DE- AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
When untapered high-gain free electron laser (FEL) reaches saturation, the exponential growth ceases and the radiation power starts to oscillate about an equilibrium. For a high-gain tapered FEL, although the power is enhanced after the first saturation, it is known that there is a so-called second saturation point where the FEL power growth stops. In addition to the sideband instability, lack of transverse radiation focusing in the post-saturation regime can be another major reason leading to occurrence of the second saturation. In this paper we study the transverse diffraction effect and its impact on tapered FEL in the post-saturation regime. The study is carried out analytically together with three-dimensional numerical simulation. The numerical parameters are taken from LCLS-like electron beam and undulator system.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK056  
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THPMK060 Start-to-End Simulations of the CLARA FEL Test Facility FEL, simulation, electron, undulator 4430
 
  • D.J. Dunning, D. Angal-Kalinin, A.D. Brynes, L.T. Campbell, H.M. Castaneda Cortes, J.K. Jones, J.W. McKenzie, N. Thompson, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • D. Angal-Kalinin, A.D. Brynes, D.J. Dunning, J.K. Jones, J.W. McKenzie, B.W.J. MᶜNeil, N. Thompson, P.H. Williams
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • L.T. Campbell, B.W.J. MᶜNeil, P.T. Traczykowski
    USTRAT/SUPA, Glasgow, United Kingdom
  • B.S. Kyle
    University of Manchester, Manchester, United Kingdom
  • B.S. Kyle
    UMAN, Manchester, United Kingdom
  • J.D.A. Smith
    TXUK, Warrington, United Kingdom
 
  CLARA is a new FEL test facility being developed at STFC Daresbury Laboratory in the UK, aiming to deliver advanced FEL capabilities including few-cycle pulse generation and Fourier transform limited output. Commissioning is underway on the front-end (photo-injector and first linac) while the later stages are being procured and assembled. Start-to-end (S2E) simulations of the full facility are presented, including optimisation of the accelerator setup to deliver the required properties of one of the electron beam modes specified for FEL operation. FEL simulations are performed using the Genesis 1.3 and Puffin codes and the results are compared.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK060  
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THPMK061 Isolated Few-Cycle Pulse Generation in X-Ray Free-Electron Lasers electron, bunching, FEL, free-electron-laser 4434
 
  • D.J. Dunning, L.T. Campbell, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • L.T. Campbell, B.W.J. MᶜNeil
    USTRAT/SUPA, Glasgow, United Kingdom
  • D.J. Dunning, B.W.J. MᶜNeil, N. Thompson
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • J.D.A. Smith
    TXUK, Warrington, United Kingdom
 
  X-ray free-electron lasers are promising candidates to deliver high-brightness radiation pulses with duration significantly shorter than the present leading technique, high harmonic generation (HHG). This would extend attosecond science to probe ultrafast dynamics with even finer resolution. To do so requires breaking below a characteristic FEL timescale of typically a few hundred optical cycles, dictated by the relative slippage of the radiation and electrons during amplification. The concept of mode-locking enables this, with the mode-locked afterburner configuration predicted to deliver few-cycle pulses (~ 1 attosecond at hard X-ray). However such techniques would produce a train of closely separated pulses, while an isolated pulse would be preferable for some types of experiment. Building on previous techniques, a new concept has been developed for isolated few-cycle pulse generation and it is presented alongside simulation studies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK061  
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THPMK063 Photocathode Preparation and Characteristics of the Electron Source for the VELA/CLARA Facility cathode, plasma, electron, operation 4442
 
  • T.C.Q. Noakes, D. Angal-Kalinin, L.S. Cowie, F. Jackson, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, M.D. Roper, E.W. Snedden, R. Valizadeh, D.A. Walsh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • D. Angal-Kalinin, L.S. Cowie, F. Jackson, J.W. McKenzie, K.J. Middleman, B.L. Militsyn, R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  The VELA and CLARA front end accelerators at Daresbury are test facilities with a focus on FEL research and industrial applications of electron beams. Recently the CLARA injector has been commissioned with acceleration of beam to 50 MeV. For several years a normal conducting 2.5 cell S-band cavity RF gun operated at up to 80 MV/m has been used as the electron source for both VELA and CLARA. For further beam acceleration an S-band travelling wave 2m long cavity has been used. The gun has used several different copper cathodes throughout its operational life, employing different preparation techniques. Oxygen plasma treatment is a well-known procedure for removing hydrocarbon contamination from surfaces whereas Argon plasma treatment also removes contaminants and typically leaves a thinner oxide at the surface. In this study we compare dark current (from field emission), as measured directly after the gun, for these alternate surface preparations and also present results from post-use electron microscopy analysis of the photocathodes. Electromagnetic simulations are used to help explain the results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK063  
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THPMK068 High degree circular polarization at x-ray self-seeding FELs with crossed-planar undulators undulator, polarization, FEL, electron 4453
 
  • K. Li, H.X. Deng, Z.F. Gao, B. Liu, D. Wang
    SINAP, Shanghai, People's Republic of China
 
  Funding: Work was supported by the National Natural Science Foundation of China (11775293), the National Key Research and Development Program of China (2016YFA0401900).
The crossed undulator configuration for a high-gain free-electron laser (FEL) is well-known for the ability of versatile polarization control. However, the degree of polarization is very sensitive to power and phase between the two stages of crossed undulators. In this poster, we introduce the generation of high degree circular polarization hard x-ray FEL with crossed-planar undulator seeded by self-seeding. The reverse taper and taper undulator technology are employed for improving its performance. With the combination of high degree (>95%) circular polarization and flexibility of polarization switching, this scheme might be useful for some scientific research in the future.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK068  
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THPMK072 X-Band RF System as Linearizer for SXFEL FEL, electron, free-electron-laser, cavity 4467
 
  • J.H. Tan, W. Fang, Q. Gu, X.X. Huang, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
 
  High gradient accelerating structure is the core technology of compact linear collider facilities and compact free electron laser facilities. Meanwhile the important limitation of improving brightness in free electron laser facility is the non-linear energy spread, and the X-band accelerating structure can provide harmonic compensation in linac to linearize the bunch compression process. In this paper, a special X-band traveling-wave accelerating structure is primary designed for compact hard x-ray free electron laser facility. Then the structure is processed manufacturing, and realize high power experiment and linear bunch compression at Shanghai soft x-ray free electron laser facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK072  
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THPMK073 Multi FEL Lines with Compact Undulator Layout undulator, FEL, electron, photon 4470
 
  • D. Wang
    SINAP, Shanghai, People's Republic of China
 
  Today the high repetition rate X-ray Free Electron Lasers based on superconducting radiofrequency technologies have come to their age. Such kind of facilities are able to serve many FEL photon beamlines simultaneously with each of which have large flexibilities in selecting wavelength, intensity, polarization, coherence and other properties through independent tuning of the undulator magnets. In reality the space needed to accommodate many undulator lines could be a limiting factor of user capacity, especially for the high rep rate XFELs that tend to utilize the underground tunnel to host long superconducting accelerator machines. In this paper we present a concept of compact undulator layout for more FEL lines in the precious tunnel spaces or similar environment. Shanghai Coherent Light Facility(SCLF) is a high repe-tition rate X-ray Free Electron Lasers installed in under-ground tunnels with an overall length of more than 3 km. The concept described in this paper could be applied to the SCLF or similar FEL facilities. The design and R&D progress will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK073  
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THPMK075 A Possible Scheme for Generating High-harmonic Coherent Radiation in Storage Rings electron, bunching, radiation, storage-ring 4473
 
  • X.F. Wang, C. Feng, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
 
  A possible scheme for storage ring FEL which can introduce small energy dispersion and emittance simultaneously to generate intense coherent light in the storage rings is described. Based on a modified version of echo-enabled harmonic generation from free-electron lasers, the technique uses a dogleg and a wave-front tilted seed laser, one normal seed laser and two chicanes to make three-dimensional manipulation of the electron beam phase space, producing high-harmonic microbunching of a relativistic electron beam. Due to small energy dispersion and emittance growth, the storage rings do not need long damping time to recover the quality of the electron beams, so this scheme will significantly improve the performance of FELs based on rings. Theoretical analysis and numerical simulations demonstrate the capability of the proposed technique in Shanghai Synchrotron Radiation Facility.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK075  
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THPMK078 Corrugated Structure as a Linearizer in High Repetition Rate X-Ray Free Electron Laser Source electron, FEL, linac, simulation 4485
 
  • Z. Wang, C. Feng, D. Huang, K.Q. Zhang, M. Zhang
    SINAP, Shanghai, People's Republic of China
 
  A feasible method is proposed to compensate the high order mode (HOM) of the RF field, linearize the bunch compression process in the high repetition rate x-ray free electron laser source. In the proposed scheme, the corrugated structure is used in the superconducting linac to linearize the longitudinal phase space of the electron beam. The results show that the peak current of the electron beam will be increased from about 1 kA to over 2 kA with the charge of 100 pC.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK078  
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THPMK083 Self-Modulation of a Relativistic Electron Beam in a Wiggler electron, wiggler, radiation, free-electron-laser 4492
 
  • J.P. MacArthur
    Stanford University, Stanford, California, USA
  • J.P. Duris, Z. Huang, A. Marinelli, Z. Zhang
    SLAC, Menlo Park, California, USA
 
  Users at x-ray free-electron laser (FEL) facilities have shown strong interest in using single spike, coherent x-ray pulses to probe attosceond dynamics in atoms and molecules. Sub-femtosecond soft x-ray pulses may be obtained from an electron beam that has been modulated in a wiggler resonant with an external laser, the enhanced-SASE technique. We discuss a new way to produce this energy modulation, wherein the external laser is replaced by coherent radiation from the current spike on the tail of the electron beam. We calculate the modulation expected in a wiggler from both a single frequency perspective and a coherent synchrotron radiation (CSR) perspective.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK083  
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THPMK097 First Conceptual Design Studies of an Electron Source for Ultrafast Electron Diffraction at DELTA electron, cavity, space-charge, gun 4530
 
  • D. Krieg, S. Khan
    DELTA, Dortmund, Germany
  • K. Sokolowski-Tinten
    Universität Duisburg-Essen, Duisburg, Germany
 
  Funding: MERCUR Pr-2017-0002
Ultrafast electron diffraction (UED) is a technique to study the structural dynamics of matter, combining diffraction of electrons with sub-angstrom De-Broglie wavelength with femtosecond time resolution. The method is complementary to X-ray scattering at free-electron lasers. UED pump-probe experiments require ultrashort laser pulses to pump a sample, electron bunches with small emittance and ultrashort length to analyze the state of the sample by diffraction, as well as excellent control of the delay between them. While most UED systems are based on electrostatic electron sources in the keV regime, electrons accelerated to a few MeV in a radiofrequency photocathode gun offer significant advantages regarding emittance and bunch length due to the reduction of space charge effects. Furthermore, the longer mean free path of MeV electrons allows for thicker samples and hence a broader range of possible materials. In this paper, a first conceptual design and simulation results for a university-based UED facility with ultrashort and low-emittance MeV electron bunches are presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK097  
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THPMK098 A Tunable Narrowband Source in the Sub-THz and THz Range at DELTA radiation, electron, detector, storage-ring 4534
 
  • C. Mai, B. Büsing, S. Khan, A. Meyer auf der Heide, B. Riemann, B. Sawadski, P. Ungelenk
    DELTA, Dortmund, Germany
  • M. Brosi, J.L. Steinmann
    KIT, Karlsruhe, Germany
  • F. Frei
    PSI, Villigen PSI, Switzerland
  • C. Gerth
    DESY, Hamburg, Germany
  • M. Laabs, N. Neumann
    TU Dresden, Dresden, Germany
  • N.M. Lockmann
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Funding: Work supported by the DFG (INST 212/236-1 FUGG), the BMBF (05K13PEC, 05K16PEB) and the state of NRW.
At DELTA, a 1.5-GeV electron storage ring operated as a synchrotron light source by the TU Dortmund University, an interaction of ultrashort laser pulses with electron bunches is used to generate broadband as well as tunable narrowband radiation in the frequency range between 75 GHz and 5.6 THz. The performance of the source was studied using two different Fourier-transform spectrometers. It was demonstrated that the source can be used for the characterization and comparison of Schottky-diode based detectors, e.g., an on-chip spectrometer enabling single-shot applications.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK098  
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THPMK099 Measurement of the Laser-Induced Energy Modulation Amplitude at the Short-Pulse Facility at DELTA electron, radiation, synchrotron, experiment 4538
 
  • A. Meyer auf der Heide, B. Büsing, S. Khan, N.M. Lockmann, C. Mai, B. Riemann, B. Sawadski
    DELTA, Dortmund, Germany
 
  The short-pulse facility at the synchrotron light source DELTA operated by the TU Dortmund University employs coherent harmonic generation (CHG) to provide ultrashort pulses in the vacuum ultraviolet and terahertz regime. Here, a laser-electron interaction results in a modulation of the electron energy which is transformed into a density modulation by a magnetic chicane. Measurements of the energy modulation amplitude with different techniques including an RF phase modulation are presented. A combination of the results allow to estimate the energy spread of the electron beam.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK099  
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THPMK108 Production of Magnetized Electron Beam from a DC High Voltage Photogun cathode, solenoid, gun, electron 4567
 
  • M.A. Mamun, P.A. Adderley, J. F. Benesch, D.B. Bullard, J.R. Delayen, J.M. Grames, J. Guo, F.E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, G.A. Krafft, M. Poelker, R. Suleiman, M.G. Tiefenback, Y.W. Wang, S. Zhang
    JLab, Newport News, Virginia, USA
  • S.A.K. Wijethunga
    ODU, Norfolk, Virginia, USA
 
  Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development funding, under contract DE-AC05-06OR23177
Bunched-beam electron cooling is a key feature of all proposed designs of the future electron-ion collider, and a requirement for achieving the highest promised collision luminosity. At the Jefferson Lab Electron Ion Collider (JLEIC), fast cooling of ion beams will be accomplished via so-called 'magnetized cooling' implemented using a recirculator ring that employs an energy recovery linac. In this contribution, we describe the production of magnetized electron beam using a compact 300 kV DC high voltage photogun with an inverted insulator geometry, and using alkali-antimonide photocathodes. Beam magnetization was assessed using a modest diagnostic beamline that includes YAG view screens used to measure the rotation of the electron beamlet passing through a narrow upstream aperture. Magnetization results are presented for different gun bias voltages and for different laser spot sizes at the photocathode, using 532 nm lasers with DC and RF time structure. Photocathode lifetime was measured at currents up to 4.5 mA, with and without beam magnetization.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK108  
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THPMK110 300 kV DC High Voltage Photogun with Inverted Insulator Geometry and CsK2sb Photocathode cathode, gun, high-voltage, emittance 4571
 
  • Y.W. Wang, P.A. Adderley, J. F. Benesch, D.B. Bullard, J.M. Grames, F.E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, G.A. Krafft, G.A. Krafft, M.A. Mamun, G.G. Palacios Serrano, M. Poelker, R. Suleiman, M.G. Tiefenback, S. Zhang
    JLab, Newport News, Virginia, USA
  • G.A. Krafft, S.A.K. Wijethunga
    ODU, Norfolk, Virginia, USA
 
  Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development funding, under contract DE-AC05-06OR23177
A compact DC high voltage photogun with inverted-insulator geometry was designed, built and operated reliably at 300 kV bias voltage using alkali-antimonide photocathodes. This presentation describes key electrostatic design features of the photogun with accompanying emittance measurements obtained across the entire photocathode surface that speak to field non-uniformity within the cathode/anode gap. A summary of initial photocathode lifetime measurements at beam currents up to 4.5 mA is also presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK110  
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THPMK115 Optical Cavity R&D for Laser-Electron Interaction Applications cavity, HOM, electron, experiment 4587
 
  • X. Liu, W.-H. Huang, C.-X. Tang, L.X. Yan
    TUB, Beijing, People's Republic of China
  • R. Chiche, K. Dupraz, P. Favier, A. Martens, H. Monard, Z.F. Zomer
    LAL, Orsay, France
  • D. Nutarelli
    LAC, Orsay, France
 
  Laser-electron Inverse Compton Scattering X-ray source based on optical enhancement cavity is expected to produce higher-flux and better-quality X-rays than conventional sources, in addition, to become more compact, much cheaper than Free Electron Laser and Synchrotron Radiation. One X-ray source named ThomX is under construction at LAL, France. An electron storage ring with 50 MeV, 16.7 MHz electron beam will collide with a few picosecond pulsed laser to produce 1013 photons per second. A prototype cavity with a high finesse (F=25,100) in the picosecond regime is used to perform R & D for ThomX. We obtained 380 kW power stored in the optical cavity and mode instabilities were observed. The EOM-based frequency modulation to measure the finesse, the influence of dust on finesse, high-power experiments and other related issues are mentioned briefly. We will also describe the TTX2 (Tsinghua Thomson Scattering X-ray source) at Tsinghua University which is in design process. TTX2 prefers using an electron storage ring and an optical cavity in order to get high X-ray flux.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK115  
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THPMK123 Initial Design on the High Quality Electron Beam for the Hefei Advanced Light Source electron, emittance, bunching, solenoid 4605
 
  • R. Huang, Z.G. He, Q.K. Jia, Y. Lu, L. Wang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  Funding: Work is supported by China Postdoctoral Science Foundation (Grant No. 51627901) and Chinese Universities Scientific Fund (Contract WK2310000063)
The Hefei Advanced Light Source (HALS) was proposed as a future soft X-ray diffraction-limited storage ring with a Free Electron Laser (FEL) at National Synchrotron Radiation Laboratory (NSRL). We present a design for a high brightness electron source as an injector of a 2.4 GeV linac-based diffraction limited storage ring and a free electron laser. The electron beams with low emittance and high peak current will be generated from a photoinjector and designed to fulfill the requirement of the HALS. To compress the bunch length and enhance the pulse current, velocity bunching scenario by a deceleration injection phase is designed. Owing to a linear compression, the electron beam is expected to be extremely short with a further magnetic compression.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK123  
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THPMK124 The Radiation Source for a Pre-Bunched THz Free Electron Laser radiation, electron, undulator, FEL 4608
 
  • R. Huang, Z.G. He, Q.K. Jia, H.T. Li, W.W. Li, Y. Lu, L. Wang, Z. Zhao
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  Funding: Work is supported by National Natural Science Foundation of China (Grant No. 51627901)
Electron beam, generated in a photoinjector and bunched at terahertz (THz) frequency, will excite the coherent THz radiation when entering an undulator. We present a scheme of the radiation source for the pre-bunched THz free electron laser (FEL). The physical design of electron source is described in detail. The radiation frequency is widely tunable by both the pulse train tuning and the undulator gap tuning. It is simulation proved that the radiation power is greatly enhanced in our scheme.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK124  
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THPMK132 Generation of Terahertz Synchrotron Radiation Using Laser-Bunch Slicing at Hefei Light Source undulator, radiation, electron, synchrotron 4626
 
  • W. Xu, S.W. Wang, S.C. Zhang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  Hefei Light Source is a second-generation low-energy synchrotron light source. The low energy machine is ca- pable of generating intense Terahertz radiation through co- herent synchrotron radiation. To realize this, one method is to shorten the bunch length to the same level of its radi- ation wavelength, e.g. by adopting low-α lattice. Another method is to modulate the electron bunch to produce mi- costructure at picosecond scale and intense Terahertz co- herent synchrotron radiation can be obtained due to the in- crease ofthebunchformfactor. This techniqueis calledthe laser bunch slicing method which introduces a laser beam into an undulator to interact with the electron bunches. In this paper we report our work on the simulation of the laser bunch slicing at Hefei Light Source.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK132  
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THPMK146 Enhancement of Laser-Compton X-ray by Crab Crossing electron, luminosity, photon, scattering 4645
 
  • Y. Koshiba, R. Morita, S. Ota, M. Washio
    Waseda University, Tokyo, Japan
  • T. Higashiguchi
    Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan
  • K. Sakaue
    Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
  • J. Urakawa
    KEK, Ibaraki, Japan
 
  Funding: This work is supported by JSPS Research Fellowships for Young Scientists (17J04371).
We are going to apply crab crossing of electrons and laser photons for the enhancement of laser-Compton X-ray flux. Crab crossing will enable quasi-head-on collision and increase the luminosity. Therefore, it could be combined with an optical enhancement cavity without the interference of beams and cavity mirrors, leading to the generation of intense X-ray pulses. Calculation show more than fourfold luminosity will be achievable in our system, and could be larger depending on beam parameters. Although crab crossing in laser-Compton scattering has been already proposed*, it has not been demonstrated yet anywhere. This will be the proof-of-principle study of the crab crossing laser-Compton scattering. In this conference, we will report our laser system based on thin-disk technology, and results of crab crossing laser-Compton scattering.
*Variola Alessandro, et al. "Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators." Physical Review Special Topics-Accelerators and Beams 14.3 (2011): 031001.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK146  
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THPMK148 Design Study on Linac-bsed Laser-cmpton Scattering X-Ray Source cavity, electron, linac, photon 4651
 
  • K. Sakaue
    Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
  • M.K. Fukuda, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • Y. Koshiba
    RISE, Tokyo, Japan
  • M. Washio
    Waseda University, Tokyo, Japan
 
  We have been developing a laser-Compton scattering X-ray source using multi-bunch linac and optical enhancement cavity. This combination have a possibility to realize a high brightness compact X-ray source. A key issue of the system is around interaction point. Compatibility of electron focusing, optical cavity and X-ray path is difficult in the current setup. Thus we propose to use rf transverse deflecting cavity for crab crossing of laser and electron. In this conference, design study of the whole laser-Compton X-ray source consist of electron linac and optical enhancement cavity will be reported. The system configuration, resulting flux and brightness, and its applications will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK148  
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THPML007 An Investigation of Electron Beam Divergence from a Single DFEA Emitter Tip cathode, experiment, electron, emittance 4662
 
  • H.L. Andrews, B.K. Choi, R.L. Fleming, D. Kim, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov
    LANL, Los Alamos, New Mexico, USA
 
  Funding: We gratefully acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program for this work.
Diamond Field-Emitter Array (DFEA) cathodes are arrays of micron-scale diamond pyramids with nanometer-scale tips. DFEAs can produce high emission currents with small emittance and energy spread. At LANL, we have an ongoing program to test DFEA cathodes for the purpose of using them to generate high-current, low-emittance electron beams for dielectric laser accelerators. We have recently upgraded our cathode test chamber to use a mesh anode in place of a solid luminescent anode. In addition to allowing for downstream beam transport, this arrangement may eliminate earlier problems with reduced cathode performance due to ion back-bombardment. We are measuring divergence of the electron beam past the mesh in an effort to characterize the inherent beam divergence off the diamond tip and divergence contribution from the mesh. We will compare these observations with theoretical and modeled values.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML007  
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THPML009 Polarized Deuteron Negative Ion Source for Nuclear Physics Applications plasma, polarization, ion-source, electron 4665
 
  • V.G. Dudnikov, M.A. Cummings, R.P. Johnson
    Muons, Inc, Illinois, USA
  • A.V. Sy
    JLab, Newport News, Virginia, USA
 
  The proposed U.S. Electron-Ion Collider (EIC) provides a unique tool to explore the next frontier in Quantum Chromodynamics, the dependence of hadron structure on the dynamics of gluons and sea quarks. Polarized beams are essential to these studies; understanding of the hadron structure cannot be achieved without knowledge of the spin. The existing EIC concepts utilize both polarized electrons and polarized protons/light ion species to probe the sea quark and gluon distributions. Polarized deuterons provide an especially unique system for study by essentially providing a combination of quark and nuclear physics. We note that there are currently no operational polarized deuteron beam sources in the United States. This polarized deuteron source can serve as a polarized deuteron injector for a future EIC, with additional applications in polarimetry and polarized gas targets for experiments at CEBAF or RHIC and would be very useful for our future facilities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML009  
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THPML011 Possibilities for Fabricating Polymer Dielectric Laser Accelerator Structures with Additive Manufacturing site, acceleration, electron, lattice 4671
 
  • E.I. Simakov, R.D. Gilbertson, M.J. Herman, G. Pilania, D.Y. Shchegolkov, E.M. Walker, E. Weis
    LANL, Los Alamos, New Mexico, USA
  • R.J. England, K.P. Wootton
    SLAC, Menlo Park, California, USA
 
  Funding: Los Alamos National Laboratory LDRD Program
We present results of recent studies of new materials designed for the additive manufacturing of accelerating structures for dielectric laser accelerators (DLAs). Demonstration of a stand-alone practical DLA requires innovation in design and fabrication of efficient laser accelerator structures and couplers. Many complicated three-dimensional structures for laser acceleration (such as a long woodpile structure with couplers) are difficult to manufacture with conventional microfabrication technologies. LANL has a large effort focused on developing new materials and techniques for additive manufacturing. The materials for DLA structures must have high dielectric constant (larger than 4), low loss in the infrared regime, high laser damage threshold, and be able to withstand the electron beam damage. This presentation will discuss the development of novel infrared dielectric materials that are of interest for laser acceleration and are compatible with additive manufacturing, as well as recent advances in additive manufacturing of dielectric woodpile structures using a Nanoscribe direct laser-writing 3D printer.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML011  
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THPML018 Modeling of Self-Modulated Laser Wakefield Acceleration Driven by Sub-Terawatt Laser Pulses electron, plasma, focusing, target 4690
 
  • C.-Y. Hsieh, S.-H. Chen
    NCU, Chung Li, Taiwan
  • M.W. Lin
    National Tsing-Hua University (NTHU), Hsinchu, Taiwan
 
  Funding: This work has been supported by the Ministry of Science and Technology in Taiwan by grant MOST104-2112-M-008-013-MY3 and by grant MOST105-2112-M-007-036-MY3.
Laser wakefield accelerator (LWFA) can be achieved in a scheme in which a sub-terawatt (TW) laser pulse is introduced into a thin, high-density target*. As a result, the self-focusing and the self-modulation can greatly enhance the peak intensity of the laser pulse capable of exciting a nonlinear plasma wave to accelerate electrons. A particle-in-cell model was developed to study the sub-TW LWFA, in which a 0.6-TW laser pulse is injected into a hydrogen gas cell with a flat-top density profile. In addition to using 800-nm laser pulses, laser pulses of 1030 nm were used in simulations as they represent a viable approach to realize the sub-TW LWFA driven by high-frequency, diode-pumped laser systems**. Process of the electron injection is complicated in such a high-density plasma; however, the simulation results show that the appropriate injection and acceleration of electrons can be achieved by optimizing the length of the gas cell. When a 340-micrometer long gas cell is introduced, energetic electrons (> 1 MeV) are produced with a relatively low emittance of 3.5 pi-mm-mrad and a total charge of 0.32 nC accordingly.
* A. J. Goers et al., Phys. Rev. Lett. 115, 194802 (2015).
** E. Kaksis et al., Opt. Express 24, 25, 28915 (2016).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML018  
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THPML024 Monoenergetic Beam Generated by Laser Accelerator at Peking University proton, quadrupole, experiment, acceleration 4702
 
  • K. Zhu, J.E. Chen, Y.X. Geng, C. Li, D.Y. Li, Q. Liao, C. Lin, H.Y. Lu, W.J. Ma, Y.R. Shou, Wu,M.J. Wu, X.H. Xu, X.Q. Yan, J.Q. Yu, Y.Y. Zhao, J.G. Zhu
    PKU, Beijing, People's Republic of China
 
  An ultrahigh-intensity laser incident on a target sets up a very strong electrostatic field exceeding 100 GV/m, it will few orders magnitude shrink down the traditional radio frequency accelerators. Whereas, to build a real accelerator for routine operation, many scientific and technical challenges for laser acceleration need to overcome before they could be applied to these applications. Recently A laser accelerator− Compact Laser Plasma Accelerator (CLAPA) is being built with a beam line to deliver proton beam with the energy of 1~15MeV, energy spread of ¡À1% and 107-8 protons per pulse. The very high current proton beam is accelerated in laser ultrathin-foil interaction and transported by a beam line consisting of the electric quadruple and analyzing magnets. It makes sure the good beam qualities such as energy spread, charge, repeatability and availability of different energy, which means that for the first laser acceleration becomes a real laser accelerator. With the development of high-rep rate PW laser technology, we can now envision a compact beam therapeutic machine of cancer treatment in the near future soon.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML024  
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THPML031 Collective Acceleration of Laser Plasma in Non-stationary and Non-uniform Magnetic Field plasma, acceleration, target, experiment 4716
 
  • A.A. Isaev, C.I. Kozlovskij, E.D. Vovchenko
    MEPhI, Moscow, Russia
 
  This paper presents the new experimental results concerning acceleration of deuterium ions extracted from laser plasma in the rapid-growing nonuniform magnetic field in order to initiate the nuclear reactions D(d, n)3He and Т (d,n)4He. In order to obtain plasma a laser that generates in Q-switched mode the pulses of infrared radiation (λ = 1.06 μm) with the energy W ≤ 0.85 J and duration of ≈10 ns. In the present study, the velocity of a bunch of a laser plasma at a magnetic field induction rate of 3-108 T/s was experimentally measured, and angular distributions of accelerated particle fluxes were measured in the range from 0 to 30 degrees. The maximum and mean ion velocities were determined by the time-of-flight technique. The proposed system allows the generation of neutrons, including possibly thermonuclear ones, on counterflows using two similar magnetic accelerators located coaxially, facing each other. In this case the problem related to degradation of solid neutron-generating targets is resolved. There also occurs a possibility of fast accumulated running time of packed solid targets at using of deuteron-tritium laser targets.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML031  
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THPML033 Towards a Free Electron Laser Using Laser Plasma Acceleration electron, plasma, free-electron-laser, FEL 4723
 
  • A. Loulergue, T. André, I.A. Andriyash, C. Benabderrahmane, P. Berteaud, F. Blache, C. Bourassin-Bouchet, F. Bouvet, F. Briquez, L. Chapuis, M.-E. Couprie, D. Dennetière, Y. Dietrich, J.P. Duval, M. El Ajjouri, T.K. El Ajjouri, A. Ghaith, C. Herbeaux, N. Hubert, M. Khojoyan, C.A. Kitegi, M. Labat, N. Leclercq, A. Lestrade, O. Marcouillé, F. Marteau, P. N'gotta, D. Oumbarek, F. Polack, P. Rommeluère, M. Sebdaoui, K.T. Tavakoli, M. Valléau, J. Vétéran, C. de Oliveira
    SOLEIL, Gif-sur-Yvette, France
  • S. Bielawski, C. Evain, E. Roussel, C. Szwaj
    PhLAM/CERLA, Villeneuve d'Ascq, France
  • S. Corde, J. Gautier, J.-P. Goddet, G. Lambert, B. Mahieu, V. Malka, J.P. Rousseau, S. Sebban, K. Ta Phuoc, A. Tafzi, C. Thaury
    LOA, Palaiseau, France
  • O. S. Kononenko
    DESY, Hamburg, Germany
  • S. Smartzev
    Weizmann Institute of Science, Physics, Rehovot, Israel
 
  Since the laser invention, the advent of X-ray Free Electron Lasers (FEL) half a century later, opens new areas for matter investigation. In parallel, the spectacular development of laser plasma acceleration (LPA) with several GeV beam acceleration in an extremely short distance appears very promising. As a first step, the qualification of the LPA with a FEL application sets a first challenge. Still, energy spread and beam divergence do not meet the state-of-the-art performance of the conventional accelerators and have to be manipulated to fulfill the FEL requirement. We report here on the undulator spontaneous emission measured after a transport manipulation electron beam line, using variable permanent magnet quadrupoles of variable strength for emittance handing and a demixing chicane equipped with a slit for the energy spread. Strategies of control electron beam position and dispersion have been elaborated. The measured undulator radiation provides an insight on the electron beam properties.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML033  
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THPML042 Integrating the Lorentz Force Law for Highly-Relativistic Particle-in-Cell Simulations plasma, simulation, acceleration, radiation 4734
 
  • A.V. Higuera, J.R. Cary
    Tech-X, Boulder, Colorado, USA
  • J.R. Cary
    CIPS, Boulder, Colorado, USA
 
  Funding: This work is supported by the DOE under Grants No. DE-SC0011617 and DE-SC0012444, and by DOE/NSF Grant No. DE-SC0012584
Integrating the Relativistic Lorentz Force Law for plasma simulations is an area of current research (*, **, ***). In particular, recent research indicates that interaction with highly-relativistic laser fields is particularly problematic for current integration techniques (****). Here is presented a special-purpose integrator yielding improved accuracy for highly-relativistic laser-particle interactions. This integrator has been implemented in the particle-in-cell code VSim, and the authors present an accuracy and performance comparison with several particle push methods.
* http://aip.scitation.org/doi/abs/10.1063/1.4979989
** https://arxiv.org/abs/1702.04486
*** https://arxiv.org/abs/1710.09164
**** http://aip.scitation.org/doi/abs/10.1063/1.4905523
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML042  
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THPML043 Optimization of Dielectric Laser-Driven Accelerators electron, simulation, acceleration, plasma 4737
 
  • C.P. Welsch, M.G. Ibison, Y. Wei
    The University of Liverpool, Liverpool, United Kingdom
  • M.G. Ibison, Y. Wei, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • J.D.A. Smith
    TXUK, Warrington, United Kingdom
  • G.X. Xia
    UMAN, Manchester, United Kingdom
 
  Funding: This project has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289191.
Dielectric laser-driven accelerators (DLAs) utilizing large electric field from commercial laser system to accelerate particles with high gradients in the range of GV/m have the potential to realize a first particle accelerator ‘on a chip'. Dual-grating structures are one of the candidates for DLAs. They can be mass-produced using available nanofabrication techniques due to their simpler structural geometry compared to other types of DLAs. Apart from the results from optimization studies that indicate the best structures, this contribution also introduces two new schemes that can help further improve the accelerating efficiency in dual-grating structures. One is to introduce a Bragg reflector that can boost the accelerating field in the channel, the other applies pulse-front-tilt operation for a laser beam to help extend the interaction length.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML043  
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THPML051 Electron Acceleration by Plasma Wave in the Presence of a Transversely Propagated Laser with Magnetic Field electron, plasma, acceleration, wakefield 4749
 
  • M. Yadav, S. C. Sharma
    DELTECH, New Delhi, India
  • D.N. Gupta, M. Kaur
    University of Delhi, Delhi, India
 
  It has been revealed that a relativistic plasma wave, having an extremely large electric field, may be utilized for the acceleration of plasma particles. The large accelerating field gradient driven by a plasma wave is the basic motivation behind the acceleration mechanism. Such a plasma wave can be excited by a single laser in the form wakefield in laser-plasma interactions. In this paper, we study the enhancement of electron acceleration by plasma wave in presence of a laser* propagated perpendicular to the propagation of the wake wave. Electrons trapped in the plasma wave are effectively accelerated by the additional field of the laser combined with wakefield. The additional resonance provided by the laser field contributes to the large energy gain of electrons during acceleration. The resonant enhancement of electron acceleration has been validated by single particle simulations**. The dependence of energy gain on laser intensity, laser spot size, initial electron energy, and electron trajectories have been investigated.
* G. D. Tsakiris, C. Gahn, and V. K. Tripathi, Phys. Plasmas 7, 3017 (2000)
** Maninder Kaur, and D. N. Gupta, IEEE, 45, p 2841 - 2847, (2017)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML051  
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THPML052 Excitation of Plasma Wave by Lasers Beating in a Collisional and Mild-Relativistic Plasma plasma, electron, damping, ECR 4752
 
  • M. Kaur, D.N. Gupta
    University of Delhi, Delhi, India
 
  Funding: Work supported by Department of Science and Technology (DST), Government of India.
Excitation of plasma wave by two lasers beating in a collisional dominated relativistic plasma is investigated. We study the energy exchange between a plasma wave and two co-propagating lasers in plasma including the effect of relativistic mass change and electron-ion collisions. Two lasers, having frequency difference equal to the plasma frequency, excite a plasma beat wave resonantly by the ponderomotive force, which obeys the energy and momentum conservation*. The relativistic effect and the electron-ion collision both contribute in energy exchange between the interacting waves in the beat-wave acceleration mechanism. Our study shows that the initial phase difference between interacting waves generates a phase mismatch between lasers and plasma wave, which alters the rate of amplitude variations of the interacting waves and, hence, affects the energy exchange between the interacting waves**. This study may be crucial to design a compact plasma accelerator in low-intensity regime***.
*T. Tajima, and J. Dawson, Phys. Rev.Lett. 43, 267(1979)
**D. N. Gupta, M. S. Hur, and H. Suk, J.Appl. Phys. 100, 103101 (2006)
***M. Kaur and D. N. Gupta, EuroPhysics letter 116, 35001 (2016).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML052  
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THPML065 Preliminary Results of the Bunch Arrival-Time Monitor at SXFEL electron, pick-up, FEL, cavity 4787
 
  • J.G. Wang, B. Liu
    SINAP, Shanghai, People's Republic of China
 
  Based on an electro-optical intensity modulation detection scheme, a Bunch Arrival-time Monitor (BAM) is under study at Shanghai soft X-ray Free Electron Laser (SXFEL) to meet the high-resolution requirements of the measurement of bunch arrival time. The first BAM is installed and is being tested at the SXFEL upstream of the first short undulator (modulator) near the seed laser injection point. In this paper, we present the basic working principle, the design of the BAM system and report the preliminary test results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML065  
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THPML092 Electromagnetic and Mechanical Design of High Gradient S-Band Accelerator in TTX scattering, HOM, cavity, linac 4876
 
  • D.Z. Cao, H.B. Chen, Y. C. Du, W. Gai, W.-H. Huang, J. Shi, C.-X. Tang, P. Wang, H. Zha
    TUB, Beijing, People's Republic of China
 
  Thomson scattering x-ray source is an essential scien-tific research tool in x-ray imaging technology for vari-ous fields. Upgrading plan of replacing the 3-meter S-band linac with a shorter structure operating at higher gradient in Tsinghua Thomson scattering X-ray source (TTX) is undergoing so far, aiming to enhance the accel-erating gradient from 15 MV/m to 30 MV/m. Detailed parameters of couplers and mechanical design of acceler-ation structure are presented in this work.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML092  
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THPML099 Phase Extraction and Stabilization for Coherent Pulse Stacking cavity, controls, FPGA, feedback 4895
 
  • Y.L. Xu, W.-H. Huang, C.-X. Tang, L.X. Yan
    TUB, Beijing, People's Republic of China
  • L.R. Doolittle, Q. Du, G. Huang, W. Leemans, D. Li, R.B. Wilcox, Y. Yang, T. Zhou
    LBNL, Berkeley, California, USA
  • A. Galvanauskas
    University of Michigan, Ann Arbor, Michigan, USA
 
  Funding: This work was supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under Contract DE-AC02-05CH11231.
Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy and high average power. We model the CPS as a digital filter in the Z domain, and implement two deterministic algorithms extracting the cavity phase from limited data where only the pulse intensity is available. In a 2-stage 15-pulse CPS system, each optical cavity is stabilized at an individually-prescribed round-trip phase with 0.7 deg and 2.1 deg RMS phase errors for Stage 1 and Stage 2 respectively. Optical cavity phase control with nm accuracy ensures 1.2% intensity stability of the stacked pulse over 12 hours.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML099  
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THPML101 A Novel Double Sideband-Based Phase Averaging Line for Phase Reference Distribution System LLRF, experiment, FPGA, pick-up 4901
 
  • Z.Y. Lin, Y.-C. Du, W.-H. Huang, Z. Pan, C.-X. Tang, C.-X. Tang, Y.L. Xu, J. Yang
    TUB, Beijing, People's Republic of China
  • G. Huang
    LBNL, Berkeley, California, USA
 
  Coaxial cable based solution is one of the most important scheme in Phase Reference Distribution System. A novel double sideband-based phase averaging line has been developed in Tsinghua accelerator lab. The sender chassis generates the 2856 MHz signal as the forward signal and receives the 2856 MHz signal and the reflected double sideband signal from the receiver. The forward signal is phase-locked with the reference signal, and the forward signal and the sideband signal are adjusted by the FPGA virtual delay line. The preliminary experiments result shows the phase stability can achieve about 1% by signal distorted by the phase shifter.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML101  
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THPML115 Introduction of the Laser Intensity Measurement System for the FELiChEM detector, FEL, electron, electronics 4936
 
  • F.L. Gao, L.T. Huang, P. Lu, B.G. Sun, J.G. Wang, F.F. Wu, Y.L. Yang, T.Y. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  The FELiChEM is a new infrared free electron laser (IR-FEL) facility, which is being built in the National Synchrotron Radiation Laboratory (NSRL) in Heifei, China. The facility will provide continuously tunable pulsed laser radiation covering the mid-infrared (MIR) wavelength range from 2.5 to 50μm and the far-infrared (FIR) range from 40 to 200μm. The output macro pulsed laser width is 5-10μs and pulsed laser power is 2-10kW. In order to evaluate pulsed laser saturation time and FEL optical cavity losses, the rise time and fall time of macro pulsed laser need to be measured. Laser intensity measurement system for the FELiChEM is being designed. This system is composed of optical system, pyroelectric detector and electronics. Each module will be described in detail in this paper. The laser intensity measurement system was tested under offline and online conditions. The results showed that pulsed laser of 10μs width can be measured and the design requirement can be met with this system.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML115  
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THPML127 Alignment and Installation for the FELiChEM project alignment, FEL, network, controls 4977
 
  • W. Wang, Zhang, H.T. H.T, X.Y. He, D.R. Xu
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  Funding: Work supported by National Natural Science Foundation of China (11705199) and China Postdoctoral Science Foundation (2017M622024)
FELiChEM is a new experimental facility under construction at the University of Science and Technology of China. There are more than one hundred important devices to construct it, which core device is two free electron laser oscillators generating middle-infrared and far-infrared laser and covering the spectral range of 25-200μm. The optical cavity is an important component of oscillator which very sensitive to misalignment errors of the mirror, due to its near-concentric and symmetric structure. High precision alignment and installation is necessary to ensure the smooth implementation of the FELiChEM project. Laser tracker and Level are used to install this devices according to the alignment control network. An efficient and high-precision alignment method based on autocollimator and photoelectric auto-collimator is used to align optical cavity of oscillator. This methods is proven to be effective and meet the tolerances by multiple means.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML127  
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