TUPMF —  MC2 Poster Session   (01-May-18   16:00—17:30)
Paper Title Page
TUPMF002 A Cu Photocathode for the Superconducting RF Photoinjector of BERLinPro 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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TUPMF003 Dynamic Tuning of the APS-U Booster 5-cell Cavities 1251
 
  • G.J. Waldschmidt, M. Abliz, T.G. Berenc, D. Horanpresenter, U. Wienands
    ANL, Argonne, Illinois, USA
 
  The booster synchrotron for the APS-U is being upgraded to accommodate high-charge bunches, up to 20 nC, for extraction into the MBA lattice. The booster is required to operate at 85% efficiency in order to achieve bunch swap-out into the storage ring. In order to compensate for significant beam-loading effects as well as support a frequency ramp to achieve higher efficiency, a ferrite tuner is being considered to dynamically adjust the cavity frequency. A tuner design will be presented that spans 60 kHz and utilizes a low-loss YIG garnet similar to that used in the Recycler Ring at Fermilab.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF003  
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TUPMF005 Simulation of Inverse Compton Scattering and Its Implications on the Scattered Linewidth 1254
SUSPF014   use link to see paper's listing under its alternate paper code  
 
  • 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 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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TUPMF007 Cryogenic Testing and Initial Performance of a Helical Superconducting Undulator at the APS 1260
 
  • J.D. Fuerst, E. Gluskin, Q.B. Hasse, Y. Ivanyushenkov, M. Kasapresenter, I. Kesgin, Y. Shiroyanagi
    ANL, Argonne, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science under Contract No. DE-AC02-06CH11357.
A helical superconducting undulator (HSCU) has been installed and is presently operational at the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). We describe the final assembly and cryogenic test program which led to successful operation, representing the culmination of a two-year development effort. Details of the cryostat and cryogenic system design are presented along with as-installed performance data and a comparison with design expectations.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF007  
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TUPMF008 Design, Construction, and Magnetic Field Measurements of a Helical Superconducting Undulator for the Advanced Photon Source 1263
 
  • M. Kasa, S.J. Bettenhausen, J.D. Fuerst, E. Gluskin, Q.B. Hasse, Y. Ivanyushenkov, I. Kesgin, Y. Shiroyanagi, E. Trakhtenberg
    ANL, Argonne, Illinois, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
A helical superconducting undulator (HSCU) was developed and installed at the Advanced Photon Source (APS). Implementation of a unique design of the helical coil former allowed for a compact turn around scheme of the conductor at the ends of the device during winding. Inherent to the coil winding design was the gradual reduction of the magnitude of the magnetic field at the ends of the device. The coil former design along with the magnetic measurement results will be described.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF008  
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TUPMF010 A Conceptual Design of a Compact Wakefield Accelerator for a High Repetition Rate Multi User X-ray Free-Electron Laser Facility 1266
 
  • A. Zholents, D.S. Doran, W.G. Jansma, M. Kasa, R. Kustom, J.G. Power, N.O. Strelnikov, K.J. Suthar, E. Trakhtenberg, I. Vasserman, G.J. Waldschmidt, J.Z. Xu
    ANL, Argonne, Illinois, USA
  • S. Baturin
    Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
  • H. Perez
    IIT, Chicago, Illinois, USA
 
  Funding: Supported by U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357
A preliminary design of a collinear wakefield accelerator is described. It is assumed that the array of such accelerators will play a central role in a free-electron laser-based x-ray user facility under consideration at Argonne National Laborator [1].
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF010  
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TUPMF011 Calculation of Expected Orbit Motion Due to Girder Resonant Vibration at the APS Upgrade 1269
 
  • V. Sajaev, Z. Liu, J. Nudell, C.A. Preissner
    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.
The Advanced Photon Source (APS) is pursuing an upgrade to the storage ring that will provide electron beam with extremely low emittance. To allow users to take advantage of this small beam size, the beam orbit motion has to be kept stable to within a fraction of the beam size. To keep the beam orbit stable on a sub-micron level, one needs to carefully design magnet supports/girders so that the ground motion does not lead to excessive orbit motion due to resonant modes of magnet supports. In this paper, we will describe the process of calculating the expected orbit motion due to girder resonant vibration. First, we will present the simulation results for the girder resonant modes, then we will calculate the orbit amplification factors for the girder deformation modes, then calculate the expected orbit motion using measured ground motion spectrum. This process can be used to evaluate the design of the magnet supports.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF011  
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TUPMF012 Determination of the Ground Motion Orbit Amplification Factors Dependence on the Frequency for the APS Upgrade Storage Ring 1272
 
  • V. Sajaev, C.A. Preissner
    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.
The Advanced Photon Source (APS) is pursuing an upgrade to the storage ring that will provide electron beam with extremely low emittance. To allow users to take advantage of this small beam size, the beam orbit motion has to be kept stable to within a fraction of the beam size, which translates to sub-micron orbit stability requirement. Ground motion provides significant contribution to the overall expected beam motion, especially at lower frequencies where the ground motion has larger amplitudes. At the same time, the lattice amplification factors reduce when the ground motion becomes coherent at low frequencies. In this paper, we will present simulation of the lattice amplification factor dependence on the ground motion coherence length and show results of the ground motion coherence measurements at APS. After that, we will determine the lattice amplification factors dependence on the ground motion frequency, that can be used to calculate the expected effect of the ground motion on the orbit stability.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF012  
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TUPMF013 Optimizations of Nonlinear Beam Dynamics Performance on APS-U Lattice 1276
 
  • Y.P. Sun, M. Borland
    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.
For next-generation storage ring light sources, such as the Advanced Photon Source (APS) Multi-Bend Achromat (MBA) upgrade, the strong nonlinearities introduced by the strong chromaticity sextupoles plus the small physical apertures make it challenging to achieve large dynamic acceptance (DA) and long Touschek lifetime, even when using the on-axis swap-out injection scheme. Several different methods have been explored for nonlinear dynamics optimization. The optimization objectives variously include the chromaticities up to third order, resonance driving and detuning terms, on- and off-momentum dynamic acceptance, chromatic and geometric tune footprint, local momentum acceptance (LMA), variation of betatron oscillation invariant, Touschek lifetime, etc. In addition, optimization can be performed without errors, with selected random errors, and with sets of errors that reflect post-commissioning conditions. In this paper, these different optimization methods are compared for the nonlinear beam dynamics performance of the Advanced Photon Source upgrade (APS-U) lattice, in terms of the dynamic acceptance, local momentum acceptance, and other performance measures. The impact from different error sources is also studied.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF013  
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TUPMF014 Synchrotron Accumulation on Off-Energy Closed-Orbit with Anti-Septum or Nonlinear Kicker 1280
 
  • Y.P. Sun
    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.
Off-axis accumulation on off-energy closed-orbit (so-called synchrotron injection/accumulation) was studied and implemented in the 1990s for LEP at CERN. The idea of using pulsed multipole injection on off-energy closed-orbit was first proposed in 2014 and then developed for Swiss Light Source (SLS) upgrade in 2015. In 2017, the anti-septum was proposed for SLS upgrade injection. In this paper, two similar injection schemes are proposed which combine off-axis accumulation on off-energy closed-orbit (no betatron oscillations), with the anti-septum or pulsed nonlinear kicker schemes. Preliminary lattice solutions are developed for Advanced Photon Source upgrade (APS-U) where a special injection straight (with length of 5.8 m) is designed with horizontal dispersion of 0.15m. The impact on the ring emittance is relatively small. The injection elements are all placed in this injection straight, including 1 thin septum and 3 slow kickers (or 1 pulsed nonlinear kicker). No fast kickers are needed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF014  
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TUPMF016 Application of SVD Analysis to Deflecting Cavitiy Space Harmonics 1283
 
  • C. Yao, L. Emery, D. Hui, H. Shang, Y.P. Sunpresenter
    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.
Singular value decomposition (SVD) analysis is a powerful tool for identifying different spatial and timing variation patterns in many fields of researches. Recently we applied complex SVD method to space harmonic analysis of a 13-cell defecting cavity that is built and installed in the APS linac injector for beam phase space characterization and emittance exchange experiments. Real and imaginary space harmonics components are extracted from CST simulated data. Fields inside the iris were expressed in analytic forms and produced good agreement. Work is underway to implement the results into elegant simulation model.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF016  
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TUPMF017 Transport Line Design and Injection Configuration Optimization for the Advanced Photon Source Upgrade 1287
 
  • A. Xiao, M. Borland
    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.
On-axis swap-out injection was chosen for the Advanced Photon Source Upgrade (APS-U) to allow pushing the beam emittance to an extremely low value. The injection section configuration was optimized within a multi-dimensional parameter space and made consistent with up-to-date technical developments. The booster-to-storage ring (BTS) transport line was designed to bring the electron beam from the existing Booster to the new storage ring (SR). Due to various limitations, this new BTS line is twisted both horizontally and vertically when approaching the injection point, which introduces challenges in both geometrical and optical matching. This paper presents our simple solution to these issues. The coupling effect caused by the twisted BTS line is also discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF017  
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TUPMF018 Simulation Studies of the Helical Superconducting Undulator Installed at APS 1290
 
  • A. Xiao, V. Sajaev, Y.P. Sun
    ANL, Argonne, Illinois, USA
 
  A multi-year project at APS has resulted in construction of a helical superconducting undulator (HSCU) for installation in the ring. Before installation, simulation studies were done to ensure that APS performance will not be compromised. This paper describes the method used for calculating the HSCU's perturbation effects and the simulation results for both calculated and measured field map.
Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF018  
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TUPMF020 Demonstration of Fast, Single-shot Photocathode QE Mapping Method Using MLA Pattern Beam 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. Halavanaupresenter, 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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TUPMF021 Investigation of Options for Damping Trapped IVU Resonances 1296
 
  • R.T. Dowd
    AS - ANSTO, Clayton, Australia
  • W.J. Chi, D. Pelz
    RFS, Kilsyth, Australia
 
  Trapped resonances have been observed within the three In-Vacuum Undulators (IVUs) insertion devices at the Australian Synchrotron. These resonances can create vertical beam instability if not controlled through transverse feedback systems. Similar resonances have been observed at other synchrotron light sources around the world. Under certain conditions of undulator gap, these resonances can couple quite strongly to the beam, requiring high feedback gain. An investigation of the resonances has been carried out using 3D eigenmode and wakefield simulations to understand the resonances and determine the effectiveness of various schemes for modifying the damping the resonances.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF021  
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TUPMF022 Electron Beam Scanning in the Delta-Type Undulators for Sirius 1300
 
  • A. B. da Cruz, L. Liupresenter
    LNLS, Campinas, Brazil
 
  We report on simulation studies to analyze the possibility of scanning the electron beam, and not scanning the sample, in CDI experiments using a Delta-Type undulator in the 3GeV Sirius electron storage ring presently under construction at LNLS. This would allow much faster scans in diffraction limited storage rings such as Sirius. We study displaced beam trajectories through the undulators and analyze the effects on the emitted radiation. It is possible to show that displacements on the order of ± 500 micrometers around the center will introduce variations in the radiation spectrum that are less that 1 per cent and thus acceptable for Coherent Diffraction Imaging experiments.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF022  
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TUPMF024 Validation of the Halbach FFAG Cell of Cornell-BNL Energy Recovery Linac 1304
 
  • F. Méot, S.J. Brookspresenter, D. Trbojevic, N. Tsoupas
    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.
The optical properties of the Halbach technology based CBETA ERL return FFAG arc cell are investigated, using its 3-D OPERA field map model. This includes paraxial and large amplitude motion, tune path, study of resonances, dynamic acceptance, effects of various defects, 300-cell 10k-particle bunches 6D transmission trials. These investigations, a 2~3 year investment, have validated the Halbach technology in the linear FFAG cell application, from the point of view of the beam dynamics, so supporting its approval as the required technology for CBETA, in December 2016.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF024  
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TUPMF025 LEReC Photocathode DC Gun Beam Test Results 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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TUPMF027 Impedance Modeling for eRHIC 1309
 
  • A. Blednykh, G. Bassi, M. Blaskiewicz, C. Hetzel, V. Ptitsynpresenter, V.V. Smaluk, F.J. Willeke
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by the US DOE under contract number DE-SC0012704
The impedance budget for the eRHIC project is discussed at its earlier stage of development. As a first step, with the eRHIC lattice and beam parameters , we use the geometric impedances of the vacuum chamber components simulated for the NSLS-II project. The impedance budged will be updated next with more impedance data simulated for the optimized eRHIC vacuum components. It will allows us to keep track on the collective effects changes with more realistic components added to the ring.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF027  
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TUPMF030 Operation and Performance of NSLS-II 1312
 
  • G.M. Wang
    BNL, Upton, Long Island, New York, USA
 
  NSLS-II facility hosts 23 operating beamlines with 2 more under commissioning. The radiation sources varies, including damping wiggler, IVU, EPU, 3PW, and bending magnets. Over the past year, the storage ring performance continuously improved, including frequency feedback and photon local feedback. Machine reliability reached 96.9% for 4500 hrs operation with beam current upto 350 mA. Beam orbit short and long term stability has been significantly improved. Operation beam emittance were optimized with beamlines.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF030  
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TUPMF032 RF Conceptual Design of Normal Conducting Cavity for an eRHIC Rapid Cycling Synchrotron 1316
 
  • B. P. Xiao, M. Blaskiewicz, J.M. Brennan, D. Holmes, K.S. Smith, T. Xin, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
The Rapid Cycling Synchrotron (RCS) for the eRHIC Ring-Ring design will provide on energy injection (up to 18 GeV) of high charge, polarized electron bunches to the eRHIC electron storage ring. The RF system comprises a large number of 563MHz fundamental cavities, providing up to 45MV per turn. The cavities will operate in pulsed mode with <20% duty factor, at a repetition rate of 1 Hz. In this paper we report the conceptual RF design of the cavity.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF032  
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TUPMF034 Measuring the Electrical Center and Field Flatness of 704 MHz Deflecting Cavity for LEReC with Wire Stretching System 1320
 
  • T. Xin, J.M. Brennan, J.C.B. Brutus, K. Mernick, K.S. Smith, B. P. Xiaopresenter, A. Zaltsman
    BNL, Upton, Long Island, New York, USA
  • W. Johnson
    SBU, Stony Brook, New York, USA
  • H. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
704 MHz deflecting cavity was designed for the Low Energy RHIC electron Cooling (LEReC) project. The cavity will serve as a major component in diagnostic line. In LEReC project the requirement on the energy spread of the electron beam is extremely high (better than 10-4) and the diagnostic system has to to be designed accordingly. The 704 MHz transverse deflecting cavity provides the vertical kick to the beam after it passes through the dispersion dipole so that we can measure the energy spread of the core of the bunch. Traditional way of determining the electrical center of the cavity involves the needle pulling and integration of the signal which is prone to the cumulative error. We present the measurement result from a wire stretching system that is much more efficient and accurate compared to the bead/needle pulling method. Both simulation and experimental results are shown in this paper and the potential in further application is discussed at the end.
 
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TUPMF035 First Demonstration of the Transparent Fast-to-slow Corrector Current Shift in the NSLS-II Storage Ring 1323
 
  • X. Yang, V.V. Smaluk, Y. Tian, L. Yu
    BNL, Upton, Long Island, New York, USA
 
  To realize the full benefits of the high brightness and ultra-small beam sizes of NSLS-II, it is essential that the photon beams are exceedingly stable (a level of 10% beam size). In the circumstances of implementing local bumps, changing ID gaps, and long-term drifting, the fast orbit feedback (FOFB) requires shifting the fast corrector strengths to the slow correctors to prevent the fast corrector saturation and to make the beam orbit stable in the sub-micron level. As the result, a reliable and precise technique of fast-to-slow corrector strength shift has been developed and tested at NSLS-II. This technique is based on the fast corrector response to the slow corrector change when the FOFB is on. In this article, the shift technique is described and the result of proof-of-principle experiment carried out at NSLS-II is presented. The maximum fast corrector current was reduced from greater than 0.45 A to less than 0.04 A with the orbit perturbation within ±1 μm. Especially when the step size of the shift was below 0.012 A, the amount of noise being added to the beam was none.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF035  
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TUPMF036 Top Off of NSLS-II with Inefficient Injector 1327
 
  • R.P. Fliller, A.A. Derbenev, V.V. Smaluk, X. Yangpresenter
    BNL, Upton, Long Island, New York, USA
 
  Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy
The NSLS-II is a 3 GeV storage with a full energy injector capable of top off injection. The injector consists of a 200 MeV linac injecting a 3 GeV booster. Recent operational events have caused us to investigate 100 MeV injection into the booster. As the booster was not designed for injection at this low energy, beam loss is observed with this low energy booster injection. This beam loss not only results of overall charge loss from the train, but a change in the overall charge distribution in the bunch train. In this paper we discuss the performance of injecting into the storage ring with the inefficient charge transfer through the injector. The changes to the top off method are discussed, as well as the achieved storage ring current stability and fill pattern.
 
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TUPMF037 Development of New Operational Mode for NSLS-II Injector: Low Energy 100MeV Linac-to-Booster Injection 1330
 
  • X. Yang, A.A. Derbenev, R.P. Fliller, T.V. Shaftan, V.V. Smaluk
    BNL, Upton, Long Island, New York, USA
 
  The NSLS-II injector consists of a 200 MeV linac and a 3 GeV full-energy booster synchrotron. The linac contains five traveling-wave S-band accelerating structures driven by two high-power klystrons, with a third klystron as spare. In the event that the spare klystron is not available, the failure of one klystron will prohibit the linac from injecting into the booster as the energy is too low. Therefore, we wish to develop a new operational mode that the NSLS-II injector can operate with a single klystron providing 100 MeV beam from the linac. A decremented approach with intermediate energies 170 MeV, 150 MeV, etc., takes advantages of pre-calculated booster ramps and beam based online optimization. By lowering the booster injection energy in a small step and online optimizing at each step, we were able to achieve 100 MeV booster injection. 170 MeV operation mode of the NSLS-II injector has been implemented since May 31, 2017, with a similar overall performance compared to the standard 200 MeV operation but fewer klystron trips. 100 MeV single-klystron operation has been successfully demonstrated with 20-30% overall efficiency, which is limited by booster acceptance.  
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TUPMF038 Design Considerations for an Ultralow Emittance Storage Ring for the Canadian Light Source 1334
 
  • L.O. Dallin
    CLS, Saskatoon, Saskatchewan, Canada
 
  Demands from light source scientists for more brilliant xray beams have resulted in the emergence of 4th generation storage rings. These demands include photon beams that are highly focussed and beams with high transverse coherence. Both these requirements are achieved with ultralow electron beam emittance. The practical development of the multi-bend achromat (MBA) concept by MAX IV has spurred many synchrotron light sources around the world to develop similar machines. For existing facilities two options are available: upgrading existing machines or building a new structure. The Canadian Light Source (CLS) has explored both options and has determined a new storage ring is required. Several design options for a 3.0 GeV ring have been developed. Best results are achieved when tracking is used to optimize the phase advance through the MBA structure to reduce the impact of the sextupoles on the dynamic aperture. Structures where no geometric sextupoles are required have been achieved while producing ultralow emittances.  
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TUPMF039 Recommissioning of the Canadian Light Source Booster Synchrotron 1338
 
  • W.A. Wurtz, D. Bertwistle, L.O. Dallin, X. Shen, J.M. Vogt
    CLS, Saskatoon, Saskatchewan, Canada
 
  The Canadian Light Source booster synchrotron was originally commissioned in 2002 and has worked reliably for many years. However, the operating point was not the design operating point and the booster suffered from poor quantum lifetime at the extraction energy. The low quantum lifetime caused current loss of approximately 25% in the microseconds before extraction. We have recommissioned the booster using the design optics, and the current loss before extraction is now only 6%. In this paper, we discuss the measurements and simulations involved in our recommissioning work.  
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TUPMF040 Alignment of Current Strips at the Canadian Light Source 1342
 
  • W.A. Wurtz
    CLS, Saskatoon, Saskatchewan, Canada
  • Q.L. Zhang
    SINAP, Shanghai, People's Republic of China
 
  The Quantum Materials Spectroscopy Centre beamline at the Canadian Light Source will employ a 180 mm period elliptically polarizing undulator (EPU180), which will have significant impacts on beam dynamics with large tune shifts and reductions in dynamic aperture. Current strips mounted to the vacuum chamber are intended to mitigate the effects of EPU180 with each strip powered by an independent power supply. It is important to accurately model the current strips in order to calculate the required compensation. We model the current strips as straight wires, parallel to the electron beam, with small horizontal and vertical displacements from their nominal positions. As the real current strips are not completely straight, this is an effective model, but justified as we are mostly interested in the magnetic field integrated along the strips. By activating two strips and measuring the ratio of the two currents needed to minimize closed orbit distortion in the horizontal and vertical planes, we can find the effective horizontal and vertical displacements of the straight wires in the model. Our goal is to create an effective model of the strips from beam-based measurements.  
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TUPMF042 Design of a High Dose Rate Micro-Focused X-Ray Source 1346
 
  • X. He, S.Q. Liao, J. Long, J. Shi, W. Wang, L. Yang
    CAEP/IFP, Mainyang, Sichuan, People's Republic of China
 
  High energy X-ray computer tomography has wide application in industry, especially in quality control of complicated high-tech equipment. In many applications, higher spatial resolution is needed to discover smaller defects. Decreasing the spot size of the X-Ray source is a promising way to get higher spatial resolution. Rhodotron have been used to produce high power CW electron beam in hundreds of kilowatts level. In this paper, we propose to use an improved Rhodotron to generate high brightness electron beam with high average power. Beam dynamics study shows that when producing tens of kilowatts electron beam, the normalized RMS emittance can be lower than 10 μm, and the relative RMS energy spread can be lower than 0.2%. The beam can be focused to a spot size of about 100μm by using a series of quadruple, and converted to X-Ray by using a rotating target within several kilowatts beam power. Improved Rhodotron proposed in this paper is a good candidate of X-ray source for high resolution high energy industrial CT systems.  
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TUPMF044 First Lasing of the CAEP THz FEL Facility Driven by a Superconducting Accelerator 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.
 
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TUPMF045 Performance Optimization of a Prototype Undulator U38 Using Multi-Objective Genetic Algorithm 1353
 
  • L.G. Yan, D.R. Deng, P. Li, D. Wupresenter
    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°.
 
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TUPMF046 The Injection and Extraction Design of the Booster for the HEPS Project 1356
 
  • Y.Y. Guo, J. Chen, Z. Duanpresenter, Y. Jiao, Y.M. Peng, G. Xu
    IHEP, Beijing, People's Republic of China
 
  The HEPS booster is a 1Hz electron synchrotron. It accelerates electron bunches from 500 MeV to final energy of 6 GeV. The vertical scheme was chosen for the injection and extraction system of the booster. What's more, an injection system from storage ring is required. The layout of the injection and extraction system were introduced in this paper. The parameter optimization and other considerations are presented in detail.  
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TUPMF048 On-Axis Beam Accumulation Based on a Triple-Frequency RF System for Diffraction-Limited Storage Rings 1359
SUSPF029   use link to see paper's listing under its alternate paper code  
 
  • S.C. Jiang, Z. Duan, G. Xu
    IHEP, Beijing, People's Republic of China
 
  Since the multi-bend achromats have been applied to lattice design in the future light source to achieve ultralow emittance, strong sextupoles and concomitant nonlinearities restrict its performance to a certain extent. The empirical understanding is the exclusion of conventional off-axis injection scheme on these light sources. In this paper, we will present a new on-axis beam accumulation scheme, which is based on the triple-frequency RF system. By means of delicate superposition of RF voltage with fundamental and two other harmonic frequencies, a commodious and steady main bucket is able to be formed. The electron bunch from the injector will be kicked into the main bucket on-axis with a reasonable time offset to the circular bunch, and this process may make the minimal disturbance to the experiment users while operating on the top-up mode. The application of this scheme to the High Energy Photon Source (HEPS) will be discussed in the paper, corresponding simulation results are also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF048  
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TUPMF049 Evolution of the Lattice Design for the High Energy Photon Source 1363
 
  • G. Xu, S.Y. Chen, Y. Jiaopresenter, J.L. Li, Y.M. Peng, Q. Qin, J.Q. Wang, C.H. Yu
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is a high-energy, ultralow-emittance, kilometer-scale storage ring light source to be built in China. The HEPS lattice design has been started since 2008. In this paper we will review the evolution of the HEPS lattice design over the past ten years, focusing mainly on the linear optics design and nonlinear optimization.  
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TUPMF050 DA Optimization Experiences in the Heps Lattice Design 1367
 
  • Y. Jiao, G. Xu
    IHEP, Beijing, People's Republic of China
 
  In the past decade, the so-called diffraction-limited storage ring (DLSR) light sources were proposed, promising much better radiation performance than available in the existing third generation light sources. Regarding the very strong focusing and chromatic sextupoles that required for reaching an ultralow emittance, to optimize the nonlinear dynamics and achieve an adequate dynamic aperture is an important topic in a DLSR design. In this paper we will present some tips distilled from the DA optimization experience of the High Energy Photon Source over the past ten years, hoping it could provide some aids to other ultralow-emittance designs.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF050  
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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 1371
 
  • W. Liu, Y. Jiaopresenter
    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.  
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TUPMF052 Progress of Lattice Design and Physics Studies on the High Energy Photon Source 1375
 
  • G. Xu, X. Cui, Z. Duan, Z. Duan, Y.Y. Guo, D. Ji, Y. Jiaopresenter, J.L. Li, X.Y. Li, C. Meng, Y.M. Peng, Q. Qin, S.K. Tian, J.Q. Wang, N. Wang, Y. Wei, H.S. Xu, F. Yan, C.H. Yu, Y.L. Zhao
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is an ultralow-emittance, kilometer-scale storage ring light source to be built in China. In this paper we will introduce the progress of the physical design and studies on HEPS over the past one year, covering issues of storage lattice design and optimization, booster design, injection design, collective effects, error study, insertion device effects, beam lifetime, etc.  
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TUPMF053 Longitudinal Impedance Measurement of the Strip-Line Kicker for High Energy Photon Source (HEPS) 1379
 
  • S.K. Tian, J. Chen, Y. Jiaopresenter, H. Shi, L. Wang, N. Wang
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is a 6-GeV, kilometer-scale storage ring light source to be built in China. One of the main design challenges of the storage ring is to minimize collective instabilities associated with the impedance of small-aperture vacuum components. In this paper we present beam coupling impedance measurements obtained by the well known coaxial wire method, for the HEPS Strip-Line kicker. The frequency dependent real and imaginary parts of the distributed impedance are obtained from the measured S-parameters.  
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TUPMF054 Performance Comparison of Different Ultralow Emittance Unit Cells 1382
 
  • Y. Jiao, X.Y. Li, G. Xu
    IHEP, Beijing, People's Republic of China
 
  The available minimum emittance of a storage ring and the ring performance is closely related to the unit cell of the lattice. Up to now, several ultralow-emittance unit cells have been proposed and applied in the lattice design of the diffraction-limited storage ring light sources. In this study we quantitatively compared the performance of three typical unit cells, based on mainly the parameters of the High Energy Photon Source. The results indicate that the modified-TME unit cell with antibend and longitudinal gradient dipole allows the lowest possible emittance, given a long enough cell length.  
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TUPMF055 Phase Matching Application in Hard X-Ray Region of HEPS 1386
 
  • X.Y. Li, Z. Duan, Y. Jiaopresenter, S.K. Tian
    IHEP, Beijing, People's Republic of China
 
  For the 6 meters long straight-section of HEPS, a double collinear double-cryogenic permanent magnet undulator(CPMU) structure is designed for high energy photon users to achieve higher brightness. Angular profiles of radiation produced by the double undulator configuration has been derived analytically. The efficiency of phase shifter on improving the brightness of double-CPMU is therefore evaluated with the beam energy spread is taken into account.  
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TUPMF056 Brightness Dependence Investigation and Optimizaiton for the Heps 1390
 
  • Y. Jiao, M. Li, X.Y. Li
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is an ultralow-emittance, kilometer-scale storage ring light source to be built in China. To maximize the photon spectral brightness, one of the most important performance parameters of the light source, we investigated the dependence of brightness on different parameters, such as the natural emittance, coupling, beta functions of the undulator section, and length of the undulator section. Based on this study, we optimized the HEPS lattice by using brightness as an optimizing objective.  
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TUPMF058 Conceptual Design of HEPS Injector 1394
 
  • J.L. Li, H. Dong, Z. Duan, Y.Y. Guo, D.Y. He, Y. Jiao, W. Kang, C. Meng, S. Pei, Y.M. Peng, J.R. Zhang, P. Zhang, Z.S. Zhou
    IHEP, Beijing, People's Republic of China
 
  Abstract The High Energy Photon Source (HEPS) will be constructed in the following few years. The light source is comprised of an ultra-low emittance storage ring and a full energy injector. The energy of the storage ring is 6 GeV. The injector is comprised of a 500 MeV linac, a 500 MeV to 6 GeV booster synchrotron and transport lines connecting the machines. In the present design, the linac uses normal conducting S-band bunching and accelerating structures. The booster adopts FODO cells, has a circumference of about 454 m and an emittance lower than 40 nmrad. The injector can provide a single-bunch charge up to 2 nC at 6 GeV for the storage ring. This paper briefly introduces the conceptual design of the injector of the HEPS.  
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TUPMF059 Error Study of HEPS Booster 1398
 
  • C. Meng, D. Ji, J.L. Lipresenter, Y.M. Peng
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is a 6-GeV, ultralow-emittance light source to be built in China. The injector is composed of a 500-MeV linac and a full energy booster with 1 Hz repetition frequency. The detailed error study of the booster will be presented, including misalignment errors and closed orbit correc-tion, magnetic field errors and power supply errors. The effect of errors on closed orbit, tune, chromaticity and dynamic aperture will be discussed. The dynamic aperture with multipole errors will be presented also.  
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TUPMF060 Design of Bunch Lengthening System in Electron Linac 1401
 
  • C. Meng, Y. Jiao, J.L. Lipresenter, S. Pei, Y.M. Peng, H.S. Xu
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is a 6-GeV, ultralow-emittance light source to be built in China. The injector is composed of a linac and a full energy booster. To increase the threshold of TMCI in the booster, the HEPS linac design has been evolved with several iterations. The important middle-version design is a 300 MeV linac with rms bunch length larger than 20 ps. One bunch lengthening system is proposed and discussed in this paper.  
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TUPMF061 Physical Design of the 500 MeV Electron Linac for the High Energy Photon Source 1404
 
  • S. Pei, D.Y. He, X. Hepresenter, J.L. Li, J. Liu, X. Ma, C. Meng, X. Wang, O. Xiao, J.R. Zhang, Z.S. Zhou
    IHEP, Beijing, People's Republic of China
  • S. Shu
    Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China
 
  Funding: Work supported by the HEPS project and the National Natural Science Foundation of China (11475201). peisl@ihep.ac.cn
The High Energy Photon Source (HEPS) is a 6 GeV light source with ultra-low emittance, it is proposed to be built at Huairou district, northeast suburb of Beijing, China. A 500 MeV electron linac will be used to generate the electron beam for injection into the booster. Here the preliminary physical design of the electron linac is presented.
 
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TUPMF062 Status of HEPS Booster Lattice Design and Physics Studies 1407
 
  • Y.M. Peng, Z. Duan, Y.Y. Guo, D. Ji, Y. Jiao, J.L. Lipresenter, C. Meng, S.K. Tian, H.S. Xu
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) with an ul-tralow emittance is proposed to be built in Beijing, Chi-na. It will utilize a booster as its full energy injector. On-axis swap-out injection is chosen as the baseline injec-tion scheme for the storage ring. As required by the stor-age ring, a beam with a bunch charge up to 2.5 nC is needed to be injected in the booster. However, limited by the transverse mode coupling instability (TMCI), such a high bunch charge is challenging. To overcome this problem, a lattice with a considerable large momentum compaction factor is designed. This paper reports the lattice design and physics studies of the HEPS booster, including injection and extraction design, error studies, eddy current effects, collective effects, and so on.  
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TUPMF063 The Considerations of Improving TMCI Threshhold on HEPS Booster 1411
 
  • Y.M. Peng, J.L. Lipresenter, C. Meng, S. Pei, H.S. Xu
    IHEP, Beijing, People's Republic of China
 
  The High Energy Photon Source (HEPS) is proposed in Beijing, China. The on-axis swap-out injection scheme will be used in the storage ring mainly because of the small dynamic aperture. Therefore, the booster needs to store more than 2.5 nC bunch charge. Under this requirement, the transverse mode coupling instability (TMCI) at the injection energy becomes the bunch charge restriction in the booster. Several changes in booster and linac for improving bunch charge threshold limited by TMCI are considered. The details will be expressed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF063  
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TUPMF065 The Role of Electron-Phonon Scattering in Transverse Momentum Conservation in PbTe(111) Photocathodes 1414
SUSPF027   use link to see paper's listing under its alternate paper code  
 
  • J. K. Nangoi, T.A. Arias
    Cornell University, Ithaca, New York, USA
  • S.S. Karkare, H.A. Padmore
    LBNL, Berkeley, California, USA
  • W.A. Schroeder
    UIC, Chicago, Illinois, USA
 
  Funding: The U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams.
The state of the art in creating high quality electron beams for particle accelerator applications and next generation ultrafast electron diffraction and microscopy involves laser-generated photoemission. A high quality beam requires that electrons emerge from the surface with low mean transverse energy (MTE). Recent density-functional theory calculations by T. Li and W. A. S. [arXiv:1704.00194v1 [physics.acc-ph] (2017)] suggest that PbTe(111) will produce low-MTE photoelectrons due to the low effective electron mass associated with its electronic band structure. Based on this, we measured the distribution of photoelectrons from PbTe(111) and found the MTE to be about 20x larger than expected. To explain the apparent lack of transverse momentum conservation, we carried out many-body photoemission calculations including electron-phonon scattering. Our results are in far better agreement with the experiment, underscoring the importance of electron-phonon scattering in photoemission from PbTe(111), and suggest that cooling could mitigate the phonon effects on the MTE for this material.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF065  
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TUPMF068 Beam Dynamics on a Coupling Resonance at PETRA III 1417
 
  • I.V. Agapov, J. Keil, G. Kube, G.K. Sahoo, R. Wanzenberg
    DESY, Hamburg, Germany
  • Y.-C. Chae
    ANL, Argonne, Illinois, USA
  • A.I. Novokshonov
    TPU, Tomsk, Russia
 
  Working on a coupling resonance is a usual way of producing round beams in a synchrotron. The beam dynamics in this regime is however more complicated, and the emittance is sensitive to the working point, coupling correction, and bunch current drop with time, which complicates the operation. We present experience with optics setup for working on a coupling resonance in PETRA III, including linear and nonlinear beam optics characteristics, and the measurement of the horizontal and vertical beam emittances with a 2D interferometer. Beam dynamics on a coupling resonance for PETRA IV, the MBA upgrade of PETRA III currently under consideration, is also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF068  
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TUPMF069 Low Gain FEL Oscillator Option for PETRA IV 1420
 
  • I.V. Agapov
    DESY, Hamburg, Germany
  • Y.-C. Chae
    ANL, Argonne, Illinois, USA
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Next generation synchrotron storage rings will have electron beam density approaching that necessary for driving an XFEL. It falls short of the quality required for the high-gain x-ray regime above 1 keV, mainly due to the large energy spread and small peak current, bit is sufficient to reach low-gain regime. Here we explore the parameter space of a low gain XFEL oscillator, to establish the feasibility range of such a device for the Petra upgrade project.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF069  
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TUPMF071 Status of Impedance Modeling for the PETRA IV 1423
 
  • Y.-C. Chae, R. Wanzenberg
    DESY, Hamburg, Germany
 
  The diffraction limited synchrotron light source envisioned for the PETRA IV project will require strong focusing to produce the small emittances in both planes. The large natural chromaticity together with small dispersion will require very strong sextupoles. In order to cope with high gradient magnets the radius of vacuum chamber tends to be in the range of 10 mm, which is very small compared to the current 40-mm wide elliptic chamber. The impedance element in the PETRA III was scaled down to fit into the smaller aperture so that the short range wakepotential can be computed numerically. For instance the beam position monitor (BPM) was reduced to 60% in dimension so that it can be used in PETRA IV. Even if the actual design of hardware does not exist yet, we assume that generic feature of PETRA III model is still valid. In this paper we report the up-to-date information on impedance model of PETRA IV together with the preliminary impedance budget based on the analytical formula. We also report the specific studies carried out to understand the kickfactor scaling with the chamber aperture whose radius is in the range of 8-12 mm.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF071  
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TUPMF072 Microwave Instability and Energy Spread Measurement via Vertical Dispersion Bump in PETRA III 1427
 
  • Y.-C. Chae, D. Dzhingaev, M. Ebert, G. Falkenberg, J. Keil, G. Kube, G.K. Sahoo, M. Sprung, R. Wanzenberg, F. Westermeier
    DESY, Hamburg, Germany
  • A.I. Novokshonov
    TPU, Tomsk, Russia
 
  The recent measurement of bunch length versus current indicated that the longitudinal impedance (Z/n) is 0.15 Ω in close agreement with the impedance model*. Naive application of Keil-Schnell criteria predicts the threshold of microwave instability at 0.25 mA. Since the single bunch intensity is in the range of 0.2-2.5 mA depending on the fill-pattern of PETRA III, we expect to observe the fill-pattern dependent energy spread according to the theory. However, the 3rd generation light sources comparable to PETRA III often reported the observation which was much greater than the theoretical one. In order to induce the beam size variation we had used skew quadrupoles to generate the dispersion in vertical plane. In particular we made dispersion bump at the undulator sector so that we were able to use the X-ray optics for the precise determination of small vertical beam size. In this paper we report the experimental setup and measurement data with the estimate on the instability threshold. We also report the vertical emittance and energy spread based on the X-ray beam size measurement as well as the RF signal which was excited by the beam at the longitudinal feedback cavity.
* K. Balewski, R. Wanzenberg, "OBSERVATION OF INTENSITY DEPENDENT SINGLE BUNCH EFFECTS AT THE SYNCHROTRON LIGHT SOURCE PETRA III", Proc. of IPAC2011, p. 730.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF072  
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TUPMF073 Impedance Optimization of Small Gap Chambers for the High Single Bunch Current Operation at the Undulator Based Light Sources 1430
 
  • Y.-C. Chae
    DESY, Hamburg, Germany
 
  In the undulator based light sources the intensity limit of single bunch is often determined by the strong vertical instability caused by the wakefield in the ring, where the undulator itself is large impedance source. The optimization of transition from the large aperture to undulator's small-gap chamber is on-going research topic in an effort to reduce the vertical impedance; at the same time, the demand on single-bunch current is high from the timing-mode x-ray user community. In this paper, after showing the results obtained by exploring the parameter space guided by Stupakov's formula, we propose the linearly-segmented transition which can reduce the impedance down to 60% or less of the original linear taper. The reduction can be utilized either to increase the bunch current substantially or to install a smaller gap chamber without impacting the bunch current limit. For the definite result we considered the transition between two ellipses, namely, (a, b) = (42 mm, 21 mm) and (18 mm, 4 mm) over the length 15-30 cm in beam direction.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF073  
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TUPMF074 Control of Collective Effects by Active Harmonic Cavity in an MBA-based Light Source with Application to the PETRA Upgrade 1433
 
  • Y.-C. Chae, J. Keil
    DESY, Hamburg, Germany
 
  Based on the reference lattice for PETRA IV* we investigated collective effects with non-zero current. Out of many possibilities we firstly computed the intrabeam-scattering (IBS) effects on the emittance as well as lifetime as a function of current. The result indicated that PETRA IV would benefit from the reduced peak current when the harmonic cavity lengthens the bunch. The operating point of harmonic cavity was explored by tracking simulations as well as analytic formula. In order to compute the energy spread and bunch length we had used the known impedance function of the APS**. In this way more realistic estimation of IBS effects was expected. However, because of the complex nature of PETRA IV lattice, which includes achromatic cells for undulators, arc cells of octants and straight sectors for damping wigglers, we simplify the longitudinal dynamics by assuming the ring made of 92 multi-bend-achromat (MBA) cells. The optics is approximated as a linear-chromatic transfer map enabling fast tracking and the ring impedance is concatenated into the one location. The detailed collective effects with and without harmonic cavities are presented in the paper.
* J. Keil, "A PETRA IV Lattice Based on Hybrid Seven Bend Achromats", these proceedings.
** Y.-C. Chae and Y. Wang, "Impedance Database II for the Advanced Photon Source Storage Ring", Proc. PAC2007.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF074  
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TUPMF075 Lattice Studies of a Booster Synchrotron for PETRA IV 1436
 
  • H.C. Chao
    DESY, Hamburg, Germany
 
  Associated with an upgrade study of the PETRA III light source toward ultra low-emittance is an upgrade study of the booster synchrotron. One possible solution obtained from a scaling of the ALBA booster to a circumference of 300 m is considered. It is based on a modified FODO lattice with combined function magnets and achromat straights. In this paper a method utilizing piecewise matchings supervised and optimized with evolutionary algorithm (PMSOEA) was devised to search the lattice. Some preliminary results are shown and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF075  
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TUPMF076 Temporal X-ray Reconstruction Using Temporal and Spectral Measurements 1440
SUSPF010   use link to see paper's listing under its alternate paper code  
 
  • 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 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 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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TUPMF080 Progress on Multibunch FEL Performance at FLASH 1452
 
  • T. Hellert, Ch. Schmidt
    DESY, Hamburg, Germany
 
  At the SASE-FEL user facility FLASH, superconducting TESLA-type cavities are used for acceleration. The high achievable duty cycle allows for operating with long bunch-trains, hence considerably increasing the efficiency of the machine. However, RF induced intra-bunch-train trajectory variations were found to be responsible for significant variations of the SASE intensity within one bunch train. This work presents the latest achievements in improving the multi-bunch FEL performance by reducing the intra-bunch-train variation of RF parameters. Particular attention is given to the static and dynamic detuning of the cavities. It will be shown that the current level of LLRF control is suitable to limit the variation of RF parameters considerably.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF080  
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TUPMF081 Microphonic Detuning Induced Coupler Kick Variation at LCLS-II 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 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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TUPMF083 Influence of Intrabeam Scattering on the Emittance of PETRA III 1463
 
  • J. Keil, G. Kube, G.K. Sahoo, R. Wanzenberg
    DESY, Hamburg, Germany
 
  PETRA~III is a 6 GeV hard X-ray synchrotron radiation source at DESY in Hamburg (Germany) and is in user operation since~2010. The natural emittance of PETRA III is extremely low with 1.3 nm*rad and the coupling is typically less than 1%. PETRA III is operated with a beam current of 100 mA using two different filling modes: a continuous mode with 960 bunches and a timing mode with 40 bunches. It has been observed that the horizontal emittance depends on the filling pattern and is in timing mode slightly larger compared to the emittance in the continuous mode. Despite the high energy of 6 GeV intrabeam scattering contributes for a slight emittance growth due to the small natural emittance and coupling of the machine. The increase of the emittance as a function of the single bunch current has been measured by using different filling patterns at a fixed beam current of 100 mA. The measurements of the emittance and the lifetime as a function of the single bunch current will be compared with theoretical expectations of the emittance growth due to intrabeam scattering and the Touschek lifetime.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF083  
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TUPMF084 Optimization of the Injection Kicker Bump Leakage at PETRA III 1467
 
  • J. Keil, G. Kube, F. Obier, G.K. Sahoo, R. Wanzenberg
    DESY, Hamburg, Germany
 
  PETRA III is a third generation synchrotron light source at DESY delivering high brightness photon beams for users at 21 beam lines. It is operated at 6 GeV with a beam current of 100 mA in top-up mode and is in operation for users since 2010. An off-axis injection scheme is used to accumulate beam from the booster synchrotron DESY II in PETRA III. Three fast injection kicker magnets generate a closed orbit bump for one turn to move the stored beam near to the injection septum magnet. Ideally the orbit bump generated by the 10 µs long half-sine pulses of the kickers should be closed. Due to differences in pulse shape as well as timing and amplitude errors of the pulses there is some leakage of the injection bump which disturbs the closed orbit and affects the beam quality during top-up operation. Turn-by-turn data from the beam position monitor (BPM) system of PETRA III have been used to measure the bump leakage for different bucket positions in the filling pattern. The procedure to reduce the injection kicker bump leakage and the achieved improvement will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF084  
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TUPMF085 Status of the sFLASH Experiment 1471
 
  • C. Lechner, R.W. Aßmann, J. Bödewadt, V. Grattonipresenter, 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.
 
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TUPMF086 Status of the ARES RF Gun at SINBAD: From its Characterization and Installation towards Commissioning 1474
 
  • B. Marchetti, R.W. Aßmann, S. Baark, F. Burkart, U. Dorda, K. Flöttmann, I. Hartl, J. Hauser, J. Herrmann, M. Hüning, K. Knebel, O. Krebs, G. Kube, W. Kuropka, S. Lederer, F. Lemery, F. Ludwig, D. Marx, F. Mayet, M. Pelzer, I. Peperkorn, F. Poblotzki, S. Pumpe, J. Rothenburg, H. Schlarb, M. Titberidze, G. Vashchenko, T. Vinatier, P.A. Walker, L. Winkelmann, K. Wittenburg, S. Yamin, J. Zhu
    DESY, Hamburg, Germany
 
  The SINBAD facility (Short and INnovative Bunches and Accelerators at DESY) is foreseen to host multiple experiments relating to the production of ultra-short electron bunches and novel high gradient acceleration techniques. The SINBAD-ARES linac will be a conventional S-band linear RF accelerator allowing the production of low charge (0.5 pC - tens pC) ultra-short electron bunches (FWHM length =< 1 fs - few fs) with 100 MeV energy. The installation of the linac will proceed in stages. In this paper we report on the status of the characterization of the ARES RF gun and the installations of the related infrastructure.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF086  
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TUPMF089 Possible Upgrades of FLASH –- A View from the Accelerator-Perspective 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 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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