TUPML —  MC3 Poster Session   (01-May-18   16:00—17:30)
Paper Title Page
TUPML003 Design of an L-band Accelerating Structure for the Argonne Wakefield Accelerator Facility Witness Beam Line Energy Upgrade 1533
 
  • J.H. Shao, M.E. Conde, D.S. Doran, J.F. Power
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  The Argonne Wakefield Accelerator (AWA) facility has been devoting much effort to the fundamental R&D of two-beam acceleration (TBA) technology with two parallel L-band beam lines. Beginning from the 70 MeV drive beam line, the high frequency (C-band and above) rf power is extracted from the beam by a decelerating structure (a.k.a. power extractor), transferred to an accelerating structure in the witness beam line, and used to accelerate the 15 MeV main beam. These high frequency accelerating structures usually have a small aperture to obtain high gradient and high efficiency, making it difficult for the low energy main beam to pass. To address this issue, one proposal is to increase the main beam energy to above 30 MeV by replacing the current witness linac. A 9-cell 𝜋-mode L-band standing-wave accelerating structure has therefore been designed to meet the high shunt impedance and low cost requirements. In addition, the single-feed coupling cell has been optimized with additional symmetrical ports to eliminate field distortion. The detailed design of the new accelerating structure will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML003  
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TUPML004 Correction of Emittance Growth Due to Quad Components in Solenoids With Quad Correctors at AWA 1536
 
  • L.M. Zheng, C.-X. Tang
    TUB, Beijing, People's Republic of China
  • M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.G. Power, J.H. Shaopresenter, C. Whiteford, E.E. Wisniewski
    ANL, Argonne, Illinois, USA
 
  An asymmetrical electron beam is observed on the drive beamline at Argonne Wakefield Accelerator (AWA) due to the quad components in the solenoids. An ASTRA simulation shows that the emittance will increase when the electron beam passes through solenoids with quad errors. We use two quad correctors to correct this emittance growth. A preliminary emittance correction result is presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML004  
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TUPML005 Study of a Dielectric Disk Structure for Short Pulse Two-Beam Acceleration 1539
 
  • J.H. Shao, M.E. Conde, D.S. Doran, J.F. Power
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  Argonne Flexible Linear Collider (AFLC), a proposed 3 TeV electron-positron linear collider based on two-beam acceleration (TBA) scheme, applies a short pulse length (∼20 ns) to obtain a high accelerating gradient (267 MV/m) and a compact footprint (∼18 km). The baseline design of the main accelerator section adopts 26 GHz K-band traveling-wave dielectric-loaded accelerators (DLA) with an rf to beam efficiency 𝜂𝑟𝑓 −𝑏𝑒𝑎𝑚 of 27%. Recently, an alternative structure which is similar to a metallic disk-loaded one but with dielectric disks, noted as dielectric disk accelerator (DDA), has been investigated and optimized, leading to ∼45% improvement in 𝜂𝑟𝑓 −𝑏𝑒𝑎𝑚. To demonstrate the key technologies, an X-band prototype structure has been designed and will be tested at Argonne Wakefield Accelerator (AWA) facility with a 300 MW metallic power extractor. Detailed comparison between K-band DLA and DDA for AFLC main accelerator as well as the preliminary design of the X-band DDA prototype will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML005  
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TUPML006 Updates of the Argonne Cathode Test-stand 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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TUPML007 Short Pulse High Power RF Generation with an X-Band Dielectric Power Extractor 1546
 
  • J.H. Shao, M.E. Conde, D.S. Doran, W. Gai, W. Liu, N.R. Neveu, J.F. Power, C. Whiteford, E.E. Wisniewski, L.M. Zheng
    ANL, Argonne, Illinois, USA
  • C.-J. Jing
    Euclid TechLabs, LLC, Solon, Ohio, USA
 
  Short pulse high power rf generation is one of the key technologies for the Argonne Flexible Linear Collider (AFLC), a proposed 3 TeV electron-positron linear collider based on two-beam acceleration (TBA) scheme. Compared with metallic power extractors, dielectric structures have the potential to achieve lower fabrication cost and to withstand higher gradient. Recently, an X-band dielectric power extractor (a.k.a, DPETS) has been developed at the Argonne Wakefield Accelerator (AWA) facility and achieved 105 MW output power when driven by a high charge 8-bunch train separated by 770 ps. The design, the cold test measurement, the preliminary high power test results, and the structure inspection will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML007  
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TUPML009 Design and Test Plan for a Prototype Corrugated Waveguide 1550
 
  • G.J. Waldschmidt, D.S. Doran, G. Ha, R. Kustom, A. Nassiri, J.G. Power, A. Zholentspresenter
    ANL, Argonne, Illinois, USA
  • A.E. Siy
    UW-Madison/PD, Madison, Wisconsin, USA
 
  A cylindrical, corrugated wakefield accelerating structure with a 1 mm radius bore is being designed to facilitate sub-terahertz Čerenkov radiation produced by an elec-tron bunch propagating along the waveguide. A 220 GHz axial mode for the wakefield is being considered. The waveguide is being optimized to maximize the trailing wakefield potential while maintaining a ratio of the trail-ing potential to the peak decelerating voltage in the bunch, or transformer ratio, of approximately 5 for the door step peak current distribution [1]. In order to evalu-ate the manufacturing tolerances and perform rf and electron beam testing of the waveguide, a 21 GHz proto-type waveguide structure will be built consisting of re-configurable parts allowing modelling of various fabrica-tion errors. Measurements with an electron beam will be performed at the Argonne Wakefield Accelerator (AWA) test facility. Analysis of the experimental layout has been performed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML009  
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TUPML011 Experiments Producing Nanopatterned Electron Beams 1553
 
  • L.E. Malin, W.S. Graves, J. Spence, K. Weiss, C. Zhang
    Arizona State University, Tempe, USA
  • R.K. Li, E.A. Nanni, X. Shen, S.P. Weathersby, J. Yang
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by NSF awards 1632780 and 1231306, DOE award DE-AC02-76SF00515, and the SLAC UED/UEM Initiative Program Development Fund.
RF photoinjectors are increasingly used to image at the nanoscale in much the same way as a Transmission Electron Microscope (TEM), which are generally sub-MeV energy. We have conducted electron diffraction experiments through a thin membrane of single crystal silicon using both the TEM and photoinjector, and have been able to model and predict the diffraction patterns using the multislice method. A nanopatterned single crystal silicon grating was also imaged in the TEM in the bright field, where all but the direct beam of the diffraction pattern is blocked, giving high contrast spatial modulations corresponding to the 400 nm pitch grating lithographically etched into the silicon. Drawing from our previous multislice calculations, we determined the crystallographic orientation that maximized the contrast in this spatial modulation at the energy of the TEM, giving a bunching factor comparable to a saturated FEL. We report on these key steps toward control of radiation phase and temporal coherence in an FEL.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML011  
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TUPML014 CO2 CPA Laser Development for User Experiments in Advanced Accelerators and Radiation Sources 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 1560
 
  • P. Kumar, V. Samulyak
    SBU, Stony Brook, USA
  • V. Samulyak, K. Yupresenter
    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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TUPML016 High-Intensity Magnetron H Ion Sources and Injector Development at BNL Linac 1564
 
  • A. Zelenski, G. Atoian, T. Lehn, D. Raparia, J. Ritter
    BNL, Upton, Long Island, New York, USA
 
  The BNL magnetron-type H ion source and the injec-tor are being upgraded to higher duty-factor as a part of Linac intensity increase project [1]. The BNL magnetron source presently delivers 110 -120 mA H ion current with 650 us pulse duration and 7 Hz repetition rate. The pulse duration was increased to 1000 µs by modifications of the gas injector pulsed valve and the use of the new arc-discharge power supply (with the arc-current stabilization circuit) which improved current stability and reduced current noise. The Low Energy Beam Transport (LEBT) lines combine two beams. The first line is the polarized OPPIS (Optically Pumped Polarized H Ion Source) beam-line and the second is the high-intensity un-polarized beam-line from the magnetron source, which transports beam to the RFQ after the passage of 45 degree bending magnet. The second magnetron source was installed in the straight LEBT section in 2017, in which the polarized OPPIS beam was not planned. In this, optimal for H beam transport configuration, the beam intensity was increased to 80 mA after the RFQ. The experience of the two sources layout operation (one source in operation the second source in standby) might be useful for facilities with the high downtime cost (like high-energy collider LHC or multi-user facilities like SNS).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML016  
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TUPML017 Longitudinal Phase Space Reconstruction at FLASHForward Using a Novel Transverse Deflection Cavity, PolariX-TDS 1567
 
  • R.T.P. D'Arcy, A. Aschikhin, P. González Caminal, V. Libov, J. Osterhoff
    DESY, Hamburg, Germany
 
  The FLASHForward project at DESY is an innovative beam-driven plasma-wakefield acceleration (PWFA) experiment, aiming to accelerate electron beams to GeV energies over a few centimeters of ionized gas. These accelerated beams are assessed for their capability to drive a free-electron laser. The ultra short, low emittance, and low energy spread properties of bunches produced from certain PWFA injection schemes naturally lend themselves to this task. However, these bunch lengths, typically in the few femtosecond range, are difficult to temporally resolve with traditional diagnostic methods. In order to longitudinally diagnose these bunches it is necessary to utilise the properties of a transverse RF deflecting cavity operating in a high-frequency regime. It is proposed that this type of X-band transverse deflection system, styled the PolariX-TDS due to its novel variable polarisation feature, will be introduced to the FLASHForward beam line in order to perform these single-shot longitudinal phase space measurements. This paper will concern itself with the efficacy of longitudinally reconstructing PWFA-bunches expected at FLASHForward with this TDS, with a focus on the variable bunch properties expected from early commissioning of the experiment.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML017  
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TUPML019 Design of Multi-Alkali Photocathode Preparation System for CTFEL Facility 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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TUPML020 Beamline Design of EMuS - the First Experimental Muon Source in China 1574
 
  • Y. Bao, Y.K. Chen, Z.L. Hou, Y.P. Song, J.Y. Tang, N. Vassilopoulos, Y. Yuan, G. Zhao, L. Zhou
    IHEP, Beijing, People's Republic of China
  • H.T. Jing
    IHEP CSNS, Dongguan, People's Republic of China
 
  Funding: This work is supported by National Natural Science Foundation of China under Grants 11575217 and 11527811. Yu Bao thanks Hundred Talents Program of Chinese Academy of Science.
We report the beamline design of the Experimental Muon Source (EMuS) project in China. Based on the 1.6 GeV/100 kW proton accelerator at the Chinese Spallation Neutron Source (CSNS), EMuS will extract one bunch from every 10 double-bunch proton pulses to hit a stand-alone target sitting in a superconducting solenoid, and the secondary muons/pions are guided to the experimental area. The beamline is designed to provide both a surface muon beam and a decay muon beam, so that various experiments such as muSR applications and particle/nuclear physics experiments can be conducted. In this work we present the conceptual design and simulation of the beamlines, and discuss the future aspects of the project.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML020  
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TUPML021 A Beamline Design to Transport Laser Wakefield Electrons to a Transverse Gradient Undulator 1577
SUSPF041   use link to see paper's listing under its alternate paper code  
 
  • 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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TUPML022 Assessment of Transverse Instabilities in Proton Driven Hollow Plasma Wakefield Acceleration 1581
 
  • Y. M. Li, G.X. Xia, Y. Zhao
    UMAN, Manchester, United Kingdom
  • S.J. Gessnerpresenter
    CERN, Geneva, Switzerland
 
  Hollow plasma has been introduced into the proton-driven plasma wakefield accelerators to overcome the issue of beam quality degradation caused by the nonlinear transverse wakefields varying in radius and time in uniform plasma. It has been demonstrated in simulations that the electrons can be accelerated to energy frontier with well-preserved beam quality in a long hollow plasma channel. However, this scheme imposes tight requirements on the beam-channel alignment. Otherwise asymmetric transverse wakefields along the axis are induced, which could distort the driving bunch and deteriorate the witness beam quality. In this paper, by means of the 2D cartesian particle-in-cell simulations, we examine the potentially detrimental effects induced by the driving beam-channel offset and initial driver tilt, and then propose and assess the solutions to these driver inaccuracy issues.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML022  
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TUPML023 Amplitude Enhancement of the Self-Modulated Plasma Wakefields 1585
SUSPF042   use link to see paper's listing under its alternate paper code  
 
  • Y. M. Li, G.X. Xia, Y. Zhao
    UMAN, Manchester, United Kingdom
  • K.V. Lotov, A. Sosedkin
    Budker INP & NSU, Novosibirsk, Russia
 
  Seeded Self-modulation (SSM) has been demonstrated to transform a long proton bunch into many equidistant micro-bunches (e.g., the AWAKE case), which then resonantly excite strong wakefields. However, the wakefields in a uniform plasma suffer from a quick amplitude drop after reaching the peak. This is caused by a significant decrease of the wake phase velocity during self-modulation. A large number of protons slip out of focusing and decelerating regions and get lost, and thus cannot contribute to the wakefield growth. Previously suggested solutions incorporate a sharp or a linear plasma longitudinal density increase which can compensate the backward phase shift and therefore enhance the wakefields. In this paper, we propose a new plasma density profile, which can further boost the wakefield amplitude by 30%. More importantly, almost 24% of protons initially located along one plasma period survive in a micro-bunch after modulation. The underlying physics is discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML023  
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TUPML025 Long Lifetime Spin-Polarized GaAs Photocathode Activated by Cs2Te 1589
SUSPF049   use link to see paper's listing under its alternate paper code  
 
  • J. Bae, L. Cultrera, P. Digiacomo
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • I.V. Bazarov
    Cornell University, Ithaca, New York, USA
 
  Funding: This work was supported by the Department of Energy Grant Nos. DE-SC0016203 and NSF PHY-1461111.
High intensity and highly spin-polarized electron source is of great interest to the next generation Electron Ion Colliders. GaAs prepared by the standard activation method, which is the most widely used spin-polarized photocathode, is notorious for its vacuum sensitivity and short operational lifetime. To improve the lifetime of GaAs photocathodes, we activated GaAs by Cs2Te, a material well known for its robustness. We confirmed the Cs2Te layer forms negative electron affinity on GaAs with a factor of 5 improvement in lifetime. Furthermore, the new activation method had no adverse effect on spin-polarization. Considering Cs2Te forms much thicker activation layer (~ 2 nm) compared to the standard activation layer (~ monolayer), our results trigger a paradigm shift on new activation methods with other robust materials that were avoided for their thickness.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML025  
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TUPML026 Multi-photon Photoemission and Ultrafast Electron Heating in Cu Photocathodes at Threshold 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 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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TUPML028 Photocathodes R&D for High Brightness and Highly Polarized Electron Beams at Cornell University 1601
 
  • L. Cultrera, J. Bae, A.C. Bartnik, I.V. Bazarov, R. Doane, A. Galdipresenter, C.M. Gulliford, W. H. Li, J.M. Maxson, S.A. McBride, T.P. Moore, C. M. Pierce, C. Xu
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Cornell University is a leader in the development of photocathode materials for the production of high brightness electron beam sources for applications in large scale accelerators and small scale electron scattering experiments. During the last year we have also included Mott polarimetry to investigate long lifetime spin-polarized photocathodes materials. Another thrust of our laboratory is the exploration of ultra low emittance photocathodes at cryogenic temperatures, for which we are building a novel LHe cryogenic electron source. We will review updates from our lab across each of these areas.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML028  
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TUPML029 Novel Photocathode Geometry Optimization: Field Enhancing Photoemission Tips 1605
 
  • W. H. Li, I.V. Bazarov, C.M. Gulliford, J.M. Maxson
    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.
For photoemission sources, the extraction electric field defines the maximum achievable emission current, and hence the maximum achievable beam brightness. Recently, interest has been growing in studying photocathodes with non-flat geometries to produce local field enhancements in excess of what can be achieved with large area flat cathodes. However, such geometries cause image charge effects which require self-consistent field solvers to correctly simulate. We present a novel simulation framework which combines a full particle in cell field solver (WARP) with a fast adaptive mesh space charge particle tracker (GPT) and a parallel multi-objective genetic optimizer to explore photocathode geometries for ultra high brightnesses. A first application of this technique is also shown, namely the use of field enhanced photoemission tips to create bright beams for ultra-fast electron diffraction.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML029  
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TUPML030 Optimisation of D- Ion Production in a Multicusp Ion Source 1609
 
  • A.M. George, M.P. Dehnel, S.V. Melanson, D.E. Potkins
    D-Pace, Nelson, British Columbia, Canada
  • N. Broderick
    University of Auckland, Auckland, New Zealand
  • H.C. McDonald, C. Philpott
    BSL, Auckland, New Zealand
 
  D-Pace's multicusp ion source achieves high beam cur-rents for negative hydrogen ions in both the TRIUMF-licensed filament-powered ion source (~18 mA) and the University of Jyväskylä-licensed RF-powered ion source (~8 mA) [1]. It is well known that ion sources producing negative deuterium ions achieve lower beam currents compared to similar negative hydrogen ion sources and indeed we have found that negative deuterium ion beam currents in our sources are typically 1/3 that of negative hydrogen beam currents. The reasons behind this are not completely understood, but factors such as the magnetic field strength and the electron temperature are believed to play a major role and offer the potential for significant optimisation. In this paper, we look into the issues surrounding swapping of deuterium for hydrogen in our ion source by studying the properties of plasmas and extracted currents with different magnetic field strengths and gas flows.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML030  
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TUPML031 Characterization of Polarization-Dependent Emittance From an Array of Au Nanorods using Velocity Map Imaging Spectrometer 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 1615
 
  • F. Jafarinia, R.W. Aßmann, F. Burkartpresenter, 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 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 1622
SUSPF037   use link to see paper's listing under its alternate paper code  
 
  • 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.
 
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TUPML039 First Order Sensitivity Analysis of Electron Acceleration in Dual Grating Type Dielectric Laser Accelerator Structures 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.
 
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TUPML040 Status of the Transverse Diagnostics at FLASHForward 1630
 
  • P. Niknejadi, R.T.P. D'Arcy, A. Knetsch, V. Libovpresenter, 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.
 
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TUPML041 Two-Stage Laser-Driven Plasma Acceleration With External Injection for EuPRAXIA 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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TUPML042 Accurate Modeling of the Hose Instability in Plasma Based Accelerators 1638
 
  • T.J. Mehrling, C. Benedetti, E. Esarey, W. Leemans, C.B. Schroeder
    LBNL, Berkeley, USA
 
  Funding: US Department of Energy Contract No. DE-AC02-05CH11231
The hose instability is a long standing challenge for plasma-based accelerators. It is seeded by initial transverse asymmetries of the beam or plasma phase space distributions. The beam centroid displacement is thereby amplified during the propagation in the plasma, which can lead to an unstable acceleration process. A witness beam can itself cause hosing and/or may be affected by the hosing of the drive beam. The accurate study of hosing including a witness beam is of utmost importance to facilitate stable plasma-based accelerators. In this contribution, we discuss novel methods for the mitigation of hosing and present a new model for the evolution of the plasma centroid, which enables the accurate investigation of the hose instability of drive and witness beam pair in the nonlinear blowout regime. This work enables more precise and comprehensive studies of hosing and hence, for the potential stabilization of future compact plasma-based accelerators.
 
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TUPML045 Segmented Terahertz Driven Device for Electron Acceleration 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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TUPML046 Characterization of Self-Modulated Electron Bunches in an Argon Plasma 1645
 
  • M. Groß, P. Boonpornprasert, Y. Chen, J. Engel, J.D. Good, H. Huck, I.I. Isaev, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, R. Niemczyk, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan, Q.T. Zhao
    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
  • T.J. Mehrling, C.B. Schroeder
    LBNL, Berkeley, USA
  • I. Will
    MBI, Berlin, Germany
 
  The self-modulation instability is fundamental for the plasma wakefield acceleration experiment of the AWAKE (Advanced Wakefield Experiment) collaboration at CERN where this effect is used to generate proton bunches for the resonant excitation of high acceleration fields. Utilizing the availability of flexible electron beam shaping together with excellent diagnostics including an RF deflector, a supporting experiment was set up at the electron accelerator PITZ (Photo Injector Test facility at DESY, Zeuthen site), given that the underlying physics is the same. After demonstrating the effect* the next goal is to investigate in detail the self-modulation of long (with respect to the plasma wavelength) electron beams. In this contribution we describe parameter studies on self-modulation of a long electron bunch in an argon plasma. The plasma was generated with a discharge cell with densities in the 1013 cm-3 to 1015 cm-3 range. The plasma density was deduced from the plasma wavelength as indicated by the self-modulation period. Parameter scans were conducted with variable plasma density and electron bunch focusing.
* M. Gross et al., "Observation of the self-modulation instabil-ity via time-resolved measurements", accepted for publication at Phys. Rev. Lett.
 
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TUPML047 Optimisation of High Transformer Ratio Plasma Wakefield Acceleration at PITZ 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.  
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TUPML049 Comparison of Fourier Signal and Error Analysis Techniques for Identifying the Self-Modulation Frequency of a Proton Bunch 1651
 
  • S.J. Gessner
    CERN, Geneva, Switzerland
 
  The AWAKE experiment uses an ultra-high energy proton beam to create large amplitude wakefields for accelerating electrons in plasma. The proton beam is much longer than the plasma wavelength, and must be formed into small, sub- wavelength sized beamlets before it can effectively drive the wake. These beamlets are referred to as micro-bunches and are formed by the plasma self-modulation instability. An im- portant aspect of AWAKE is to measure the depth, frequency, and stability of the modulation, as this provides critical in- formation for establishing the presence of a high-amplitude wakefield driven by a self-modulation proton bunch. This paper discusses Fourier Analysis techniques for measuring the modulation frequency and compares error estimation techniques that work for both small and large datasets.
On behalf of the AWAKE Collaboration.
 
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TUPML051 Studies of Collision and Compression of Pulsed Plasmas Generated by Coaxial Accelerators 1653
 
  • T. Manegold, C. Benzing, M. Iberler, J. Jacoby, P. Mahmoodi Tavana, A. Müller-Münster, B. Podßus
    IAP, Frankfurt am Main, Germany
 
  This contribution is about our recent studies of collision and compression of plasma sheaths, generated by coaxial plasma accelerators. One application is the development of a pulsed ion source producing high ion currents, coming along with high electron densities. The experiment is built up of an energy storage with up to 1,35kJ with a 2% Hydrogen in Helium gas mixture as working gas. The small fraction of Hydrogen is necessary to use the linear Stark-broadening of the H-line to determine the electron density, which is in the range up to 1015cm-3. By the collision of two plasma sheaths in an angle of 180°, the electron density has been increased by a factor of 2.5 compared to the single plasma sheath. As an alternative, the compression of the plasma by funnel geometries has been studied. As has been found, the achieved electron densities are more than a magnitude higher, compared to the values of the plasma collision. Thus, the H-line is broadened too high to be used. Alternatively, the broadening of a copper line by the quadratic Stark-effect has been calibrated and used to determine those high electron densities of about 1018cm-3.  
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TUPML052 Characterisation of the Second Stable Orbit Generated by Transverse Resonance Island Buckets (TRIBs) 1656
 
  • F. Kramer, P. Goslawski, A. Jankowiak, M. Ries, M. Ruprecht, A. Schälicke
    HZB, Berlin, Germany
 
  Funding: Federal Ministry of Education and Research
Operating the storage ring near a transverse tune resonance can generate TRIBs in the corresponding phase space, providing a second orbit twisting around the standard orbit. TRIBs as a bunch separation scheme in combination with the proposed variable bunch length storage ring BESSY VSR* represent a promising alternative to dedicated single or few bunch operation modes. The injection efficiency and stability of the two orbits at BESSY II and MLS are almost on par with and the lifetime at about 70 % of the standard user mode. Results from simulations and measurements of our present island optics will be presented. Beam parameters like the betatron motion, dispersion and emittance of both the core and island orbit will be discussed as well as the separation between the island and the core orbit. At BESSY II a dedicated test week together with the friendly users took place in the first week of February, 2018.
* A. Jankowiak et al., eds., BESSY VSR Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, June 2015. DOI: 10.5442/R0001
 
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TUPML053 The BERLinPro SRF Photoinjector System - From First RF Commissioning to First Beam 1660
 
  • A. Neumann, D. Böhlick, M. Bürger, P. Echevarria, A. Frahm, H.-W. Glock, F. Göbel, S. Heling, K. Janke, A. Jankowiak, T. Kamps, S. Klauke, G. Klemz, J. Knobloch, G. Kourkafas, J. Kühn, O. Kugeler, N. Leuschner, N. Ohm, E. Panofski, H. Plötz, S. Rotterdam, M.A.H. Schmeißer, M. Schuster, H. Stein, Y. Tamashevich, J. Ullrich, A. Ushakovpresenter, J. Völker
    HZB, Berlin, Germany
 
  Funding: The work is funded by the Helmholtz-Association, BMBF, the state of Berlin and HZB.
Helmholtz-Zentrum Berlin (HZB) is currently constructing a high average current superconducting (SC) ERL as a prototype to demonstrate low normalized beam emittance of 1 mm-mrad at 100 mA and short pulses of about 2 ps. To attain the required beam properties, an SRF based photo-injector system was developed and during the past year underwent RF commissioning and was setup within a dedicated diagnostics beamline called Gunlab to analyze beam dynamics of both, a copper cathode and a Cs2KSb cathode as well as their quantum efficiency at UV and green light respectively. The medium power prototype - a first stage towards the final high power 100 mA design - presented here features a 1.4 x λ/2 cell SRF cavity with a normal-conducting, high quantum efficiency CsK2Sb cathode, implementing a modified HZDR-style cathode insert. This injector potentially allows for 6 mA beam current and up to 3.5 MeV kinetic energy, limited by the modified twin TTF-III fundamental power couplers. In this contribution, the first RF commissioning results of the photo-injector module will be presented including dark current analysis as well as measured beam properties with an initially installed Copper cathode.
 
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TUPML054 Microbeam Irradiation System with a Dielectric Laser Accelerator for Radiobiology Research 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.
 
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TUPML055 Beam Optics Designs of a Strecher Ring and a Transfer Line for J-PARC Slow Extraction 1667
 
  • M. Tomizawa, R. Muto, T. Ogitsu
    KEK, Ibaraki, Japan
  • A. Konaka
    TRIUMF, Vancouver, Canada
 
  The J-PARC main ring (MR) provides 30 GeV high intensity beams for neutrino experimental facility (NU) by fast extraction and hadron experimental facility (HD) by slow extraction. It is a serious issue to ensure sufficient integrated proton number on target (POT) for each facility. A stretcher ring (ST) can solve this serious problem. A beam accelerated by the MR is transferred to the ST and is slowly extracted over several second. While the beam is slowly extracted in the ST, the MR can accelerate and deliver a beam to the NU. The ST is put above the MR and fitted in the MR tunnel. Arc sections in the ST consist of superconducting combined function magnets (dipole, quadrupole and sextupole components), and separated function quadruple and sextupole magnets (hybrid lattice). A 30 GeV beam transfer line (BT) from the MR to the ST uses superconducting combined magnets with dipole and quadrupole functions to shorten the BT. The transferred beam is injected into an arc section in the ST. The adoption of the superconducting magnets in the ST and the BT saves operation cost drastically. Beam optics designs for the ST and the BT will be described in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML055  
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TUPML059 Slice Energy Spread Optimization for a 5 GeV Laser-Plasma Accelerator 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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TUPML060 Three-Dimentional Spiral Beam Injection for a Compact Storage Ring 1673
 
  • H. Iinuma
    Ibaraki University, Hitachi, Ibaraki, Japan
  • M.R. Abdul
    Sokendai, Ibaraki, Japan
  • Y. Fukao, K. Furukawa, H. Hisamatsu, T. Mibe, H. Nakayama, S. Ohsawa, K. Oide, K. Sasaki
    KEK, Tsukuba, Japan
 
  Funding: This work is supported by JSPS KAKENHI Grant Numbers JP26287055 and JP 23740216.
A newly developed three-dimensional spiral injection scheme for beam insertion into a compact (medical MRI size) solenoidal storage ring is introduced. This is a one of key R&D items for a new planned muon g-2/EDM experiment at J-PARC, which aims to measure g-2 to a factor 5 better statistical precision and a factor of 100 better sensitivity for the electric dipole moment measurement (EDM) compared to the previous experiments. The new scheme provides a smooth injection utilizing a radial solenoidal fringe field, without causing any error field in the storage volume. Magnetic pulsed kicker will guide and set the beam in the storage field volume. The strongest point of this new scheme is that any source of the electric field is removed in this scheme to perform ideal EDM measurement. We have performed a test bench experimental work to demonstrate a feasibility of this new injection scheme. Instead of the muon beam, we inject electron beam, from an electron-gun, into the solenoid magnet, and detect three-dimensional spiral beam trajectory inside of the storage chamber by CCD camera. We will discuss outline of a new injection scheme and the latest results from the test bench works.
*H. Iinuma et al.,Nuclear Instruments and Methods in Physics Research A, 832, 51-62 (2016)
 
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TUPML061 Study of Mean Transverse Energy of (N)UNCD with Tunable Laser Source 1677
SUSPF050   use link to see paper's listing under its alternate paper code  
 
  • 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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TUPML062 A Wedge Test in MICE 1680
 
  • T.A. Mohayai
    IIT, Chicago, Illinois, USA
  • D.V. Neuffer
    Fermilab, Batavia, Illinois, USA
  • P. Snopok
    Illinois Institute of Technology, Chicago, Illlinois, USA
  • D.J. Summers
    UMiss, University, Mississippi, USA
 
  Emittance exchange mediated by wedge absorbers is required for longitudinal ionization cooling and for final transverse emittance minimization for a muon collider. A wedge absorber within the MICE cooling channel could serve as a demonstration of the type of emittance exchange needed for 6-D cooling, including the configurations needed for muon colliders. Parameters for this test have been explored in simulation and applied to experimental configurations using a wedge absorber in the MICE beam. A wedge absorber has been constructed and placed in MICE and data has been collected for both direct emittance exchange, where the longitudinal emittance decreases, and reverse emittance exchange, where the transverse emittance decreases. The simulation studies that led to the magnet configurations and beam configurations are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML062  
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TUPML063 A Non-parameteric Density Estimation Approach to Measuring Beam Cooling in MICE 1684
SUSPF033   use link to see paper's listing under its alternate paper code  
 
  • T.A. Mohayai
    IIT, Chicago, Illinois, USA
  • D.V. Neuffer
    Fermilab, Batavia, Illinois, USA
  • P. Snopok
    Illinois Institute of Technology, Chicago, Illlinois, USA
 
  The goal of the international Muon Ionization Cooling Experiment (MICE) is to demonstrate muon beam ionization cooling for the first time. It constitutes a key part of the R&D towards a future neutrino factory or muon collider. The intended MICE precision requires development of analysis tools that can account for any effects (e.g., nonlinearities) which may lead to inaccurate cooling measurements. Non-parametric density estimation techniques, in particular, kernel density estimation (KDE), allow very precise calculations of the muon beam phase-space density and its increase as a result of cooling. In this study, these density estimation techniques and their application to measuring the reduction in muon beam phase-space volume and amplitude in MICE are investigated.  
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TUPML064 Staged Two Beam Acceleration Beam Line Design for the AWA Facility 1688
SUSPF040   use link to see paper's listing under its alternate paper code  
 
  • 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.
 
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TUPML065 Phase Space Density Evolution in MICE 1692
 
  • D. Rajaram
    Illinois Institute of Technology, Chicago, Illinois, USA
  • V. Blackmore
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
 
  Funding: STFC, DOE, NSF, INFN, and CHIPP
The Muon Ionization Cooling Experiment (MICE) collaboration will demonstrate the feasibility of ionization cooling, the technique proposed to cool the muon beam at a future neutrino factory or muon collider. The muon beam parameters are measured before and after the cooling cell using high precision scintillating-fibre trackers in a solenoidal magnetic field. Position and momentum reconstruction of each muon in MICE allows the development of several alternative figures of merit in addition to emittance. Contraction of the phase-space volume of the sample, or equivalently the increase in phases-pace density at its core, is an unequivocal cooling signature. Single-particle amplitude, defined as a weighted distance to the sample centroid, can be used to probe the change in density in the core of the beam. Alternatively, non-parametric statistics provide reliable methods to estimate the entire phase-space density distribution and reconstruct probability contours. The aforementioned techniques, robust to transmission losses and sample non linearities, are ideal candidates for a cooling measurement in MICE. Preliminary results are presented here*.
*Submitted by the MICE Speakers bureau, to be prepared and presented by a MICE member to be selected in due course
 
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TUPML066 Progress on Beam-Plasma Effect Simulations in Muon Ionization Cooling Lattices 1696
 
  • P. Snopok
    Illinois Institute of Technology, Chicago, Illinois, USA
  • J.S. Ellison
    IIT, Chicago, Illinois, USA
 
  Funding: Work supported by the Department of Energy.
New computational tools are essential for accurate modeling and simulation of the next generation of muon-based accelerators. One of the crucial physics processes specific to muon accelerators that has not yet been simulated in detail is beam-induced plasma effect in liquid, solid, and gaseous absorbers. We report here on the development of required simulation tools and their applications to studying the properties of plasma and its effects on the beam in muon ionization cooling channels.
 
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TUPML067 Recent Results from the Study of Emittance Evolution in MICE 1699
 
  • V. Blackmore
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
 
  Funding: STFC, DOE, NSF, INFN, and CHIPP
The Muon Ionization Cooling Experiment (MICE) has measured the evolution of emittance due to ionization energy loss. Muons were focused onto an absorber using a large aperture solenoid. Lithium-hydride and liquid hydrogen-absorbers have been studied. Diagnostic devices were placed upstream and downstream of the focus, enabling the phase-space coordinates of individual muons to be reconstructed. By observing the properties of ensembles of muons, the change in beam emittance was measured. Data taken during 2016 and 2017 are currently under study to evaluate the change in emittance due to the absorber for muon beams with various initial emittance, momenta, and settings of the magnetic lattice. The current status and the most recent results of these analyses will be presented.
 
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TUPML068 The European Spallation Source Neutrino Super Beam Design Study 1702
 
  • M. Dracos
    IPHC, Strasbourg Cedex 2, France
 
  Funding: This project is now supported by the COST Action CA15139/EuroNuNet and EU/H2020 innovation programme ESSnuSB under grant agreement No 777419.
ESSnuSB proposes to use the proton linac of the European Spallation Source (ESS) currently in construction in Lund (Sweden) to produce a very intense neutrino super beam, in parallel with the spallation neutron production. The ESS linac is expected to be operational by 2023 delivering 5 MW average power, 2 GeV proton beam, with 2.86 ms long pulses at a rate of 14 Hz. The primary proton beam-line completing the linac will consist of an accumulator ring to compress the beam pulses to 1.3 µs and a switchyard to distribute the protons onto the target station. The secondary beam-line producing neutrinos will consist of a four-horn/target station, a decay tunnel and a beam dump. A megaton scale water Cherenkov detector will be located at a baseline of about 500 km in one of the existing mines in Sweden and it will measure the neutrino oscillations. ESSnuSB was recently granted by the European H2020-INFRADEV program to start beginning of 2018 a 4-year design study on the feasibility of such facility. This paper presents the objectives, the steps and the organization of the ESSnuSB DS.
 
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TUPML070 Laser Ablation Plasma with Solenoid Field Confinement 1706
SUSPF048   use link to see paper's listing under its alternate paper code  
 
  • 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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TUPML071 Experimental Performance of the Chopper for the ESS Linac 1709
 
  • G. Torrisi, L. Allegra, A.C. Carusopresenter, G. Castro, L. Celona, G. Gallo, S. Gammino, O. Leonardi, A. Longhitano, D. Mascali, L. Neri, S. Passarello, G. Sorbello
    INFN/LNS, Catania, Italy
 
  At the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud (INFN-LNS) the beam commissioning of the high intensity Proton Source for the European Spallation Source (PS-ESS) was completed in November 2017. The ESS requires a high intensity proton beam (74 mA pulsed at 14 Hz of repetition rate), with fast Beam pulse rise/fall time (< 20 µs). In order to meet the project requirement, an electrostatic chopping system has been used in the Low Energy Beam Transport (LEBT). The design of the control system was done also to be the main element of the fast beam abort system and taking into account the radiation issue in the accelerator tunnel. This paper describes the performances of the chopper. The experimentally-achieved rise/fall times of the beam pulses measured by using an AC Current Transformer (ACCT) at the end of the LEBT collimator, are presented. An experimental investigation of the effects of different amounts and types of gas injected into the LEBT (for the sake of space charge compensation) has been carried out with respect to the beam and chopper parameters.  
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TUPML073 Ion Source and Low Energy Beam Transport Line Final Commissioning Step and Transfer from INFN to ESS 1712
 
  • L. Celona, A. Amato, G. Calabrese, A.C. Caruso, G. Castro, F. Chines, S. Gamminopresenter, O. Leonardi, A. Longhitano, G. Manno, S. Marletta, D. Mascali, A. Maugeri, M. Mazzaglia, A. Miraglia, L. Neri, S. Passarello, A. Seminara, D. Siliato, A. Spartà, G. Torrisi
    INFN/LNS, Catania, Italy
 
  At the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud (INFN-LNS), the beam commissioning of the high intensity Proton Source for the European Spallation Source (PS-ESS) was completed in November 2017. All requirements have been satisfied and certified by the European Spallation Source (ESS). In the last step of the commissioning a complete characterization of the source has been carried out and some results are hereinafter reported. The shipment of the source was done in December 2017, followed by the installation in January while the beam commissioning is foreseen during summer 2018. The paper describes the final commissioning steps at INFN-LNS, the procedure adopted for a safe transfer of the equipment, the transfer of knowledge needed for the operation and the maintenance.  
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TUPML074 Resonant Excitation of Accelerating Field in Dielectric Corrugated Waveguide 1715
 
  • A. Lyapin, S.T. Boogert, K. Lekomtsev
    JAI, Egham, Surrey, United Kingdom
  • A. Aryshev
    KEK, Ibaraki, Japan
  • A.A. Tishchenko
    MEPhI, Moscow, Russia
 
  Funding: This project has received funding from the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 655179.
Beam driven dielectric wakefield accelerators (DWAs) [*] typically operate in the terahertz frequency range, which pushes the plasma breakdown threshold for surface electric fields into the multi GV/m range. DWA technique allows one to accommodate a significant amount of charge per bunch, and opens access to conventional fabrication techniques for the accelerating structures. Resonant excitation of coherent Cherenkov radiation in DWA by a multi-bunch beam was used for selective resonant mode excitation [**] and enhancement of accelerating wakefield [***]. We investigate the resonant excitation of Cherenkov Smith-Purcell radiation [****] in a corrugated cylindrical waveguide by a multi-bunch electron beam. The accelerating field is calculated using Particle in Cell simulations and some basic post-processing is done in order to estimate the possible enhancement of the accelerating field. The aim of this work is to investigate regimes of the resonant excitation that can potentially produce accelerating gradients above 1 GV/m.
* C. Jing, Rev. Acc. Phys. and Tech. 9, 127 (2016).
** G. Andonian, APL 98, 202901 (2011).
*** J.G. Power, PRSTAB 3, 101302 (2000).
**** A.A. Ponomarenko, A.A. Tishchenko, NIMB 309, 223 (2013).
 
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TUPML075 Development of Target/ion Source for Li-8 Beam at KOMAC* 1718
 
  • J.J. Dang, Y.-S. Cho, H.S. Kim, H.-J. Kwon, P. Lee, S. Lee, Y.G. Song
    Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea
 
  Funding: This work has been supported through KOMAC operation fund of KAERI by MSIT and the NRF of Korea grant funded by the Korea government (MSIT) (No. NRF-2017M2A2A6A02071070).
A target/ion source (TIS) for Li-8 isotope beam has been developed at Korea Multi-purpose Accelerator Complex (KOMAC). The TIS was designed based on various numerical studies such as Monte Carlo simulation for Li-8 yield estimation, an ionization efficiency calculation of a surface ionization ion source and thermal analysis by a power balance model. Then, it was fabricated that a prototype of the TIS which consists of a beryllium oxide (BeO) target, a graphite target container, a tantalum target heater and a rhenium surface ion source. Also, the target heater and the surface ion source were heated to designed operation temperatures. In addition, it has been designed and constructed that an online test facility including Li-8 beam optics and diagnostics.
 
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TUPML076 Installation, Commissioning and Characterization of EBIS-SC as a Short Pulsed Proton Source at KOMAC 1721
 
  • S. Lee, Y.-S. Cho, H.S. Kim, H.-J. Kwonpresenter
    Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea
 
  Funding: This work has been supported through KOMAC operation fund of KAERI by MSIT (Ministry of Science and ICT)
Neutron source is applicable to various fields in basic/applied science and industries. There are several neutron sources in the world such LENS, SNS, J-PARC, ISIS and ESS either for short or long pulsed neutron. At Korea Multipurpose Accelerator Complex (KOMAC), to provide wide ranges of research opportunities to beam user, a 100 MeV proton linac based pulsed neutron source is planned for both long and short pulses of neutron source. Currently, the 100 MeV proton linac is operational with a 2 ms long pulsed proton injector, i.e. a microwave ion source. We will upgrade our injector by combining the already existing microwave ion source with a EBIS-SC (Superconducting Electron Beam Ion Source from Dreebit GmbH) for short pulses (< 1 us) of proton. This planned injector will work one at the time and provide long/short pulses of accelerated proton hitting a target to emit correspondingly long/short neutron pulses. Main modification on the proton injector is the EBIS-SC, so in this paper we report the installation, and commission of the EBIS-SC test bench at KOMAC. And the characterization of the EBIS-SC is described in detail.
 
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TUPML077 Development of Physical Processes in Geant4 for Simulation of ISOL Target-Ion-Source System 1724
 
  • P. Lee, Y.-S. Cho, J.J. Dang, H.S. Kim, H.-J. Kwon, S. Lee, Y.G. Song, S.P. Yun
    Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea
 
  Funding: This work has been supported through KOMAC operation fund of KAERI and the NRF of Korea grant funded by the Korea government (MSIT) (No. NRF-2017M2A2A6A02071070).
Geant4 physical processes for simulating diffusion and effusion of radioactive ions in matter have been developed for optimizing ISOL target-ion-source (TIS) system. The developed processes simulate motions of radioactive ions with sub-eV kinetic energy in the TIS geometry. The processes consist of diffusion, effusion, and radioactive decay modules, and they are designed to work seamlessly with other implemented physics lists, extending capability of the Geant4 toolkit to more complicated applications in the field of nuclear physics. The diffusion probability is analytically calculated by using the well-known Fick's formula. The effusive flow of neutral atoms is interpreted in terms of kinetic molecular theory of gases, where the interaction between atoms and the wall of a target container is described by employing Lorentz-Lambert model. By the help of newly implemented processes, it is able to simulate the release of radioactive ions from the irradiation of a proton beam on the TIS system with different geometrical parameters in a single environment. Here, we present the status of the development and plans for further improvements.
 
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TUPML078 Fast Quadrupole Beam Based Alignment Using AC Corrector Excitations 1727
 
  • Z. Martí, G. Benedetti, U. Irisopresenter
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
 
  A novel method to perform Beam Based Alignment has been tested at ALBA using the 10kHz fast acquisition BPMs together with an AC excitation of the corrector magnets allowing to speed up the beam based alignment process. The former approach relies on software synchronization and tango device servers to execute a series of DC corrector magnets and quadrupoles settings designed to avoid the quadrupole hysteresis effects. The approach that we present here is simpler, gives the same level of accuracy and precision and speeds up the measurement by a factor 10. The total measurement time has changed from 5 hours to 10 minutes.  
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TUPML079 A Start to End Simulation of the Laser Plasma Wakefield Acceleration Experiment at ESCULAP 1731
SUSPF043   use link to see paper's listing under its alternate paper code  
 
  • K. Wang, C. Bruni, K. Cassou, V. Chaumat, N. Deleruepresenter, 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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