Keyword: FEL
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MOPAB018 SASE Gain-Curve Measurements with MCP-Based Detectors at the European XFEL detector, photon, undulator, radiation 96
 
  • E. Syresin, O.I. Brovko, A.Yu. Grebentsov
    JINR, Dubna, Moscow Region, Russia
  • W. Freund, J. Grünert, J. Liu, Th. Maltezopoulos, D. Mamchyk
    EuXFEL, Schenefeld, Germany
  • M.V. Yurkov
    DESY, Hamburg, Germany
  
  Radiation detectors based on microchannel plates (MCP) are used for characterization of the Free-Electron Laser (FEL) radiation and measurements of the Self-amplified spontaneous emission (SASE) gain curve at the European XFEL. Photon pulse energies are measured by the MCPs with an anode and by a photodiode. There is one MCP-based detector unit installed in each of the three photon beamlines downstream of the SASE1, SASE2, and SASE3 undulators. MCP detectors operate in a wide dynamic range of pulse energies, from the level of spontaneous emission up to FEL saturation. Their wavelength operation range overlaps with the whole range of radiation wavelengths of SASE1 and SASE2 (from 0.05 nm to 0.4 nm), and SASE3 (from 0.4 nm to 5 nm). In this paper we present results of SASE gain-curve measurements by the MCP-based detectors.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB018  
About • paper received ※ 18 May 2021       paper accepted ※ 17 August 2021       issue date ※ 23 August 2021  
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MOPAB040 Gain of Hard X-Ray Fel at 3 GeV and Required Parameters electron, undulator, laser, focusing 178
 
  • L.H. Yu
    BNL, Upton, New York, USA
  
  We develop a tool for the calculation to study the conditions for a hard x-ray FEL oscillator based on an electron beam in the medium energy range from 3 to 4.5 GeV. We show that the approach developed by K.J. Kim et al. for the small-signal low gain formula can be modified so that the gain can be derived without taking the "no focusing approximation" adopted in the approach so that a strong focusing can be applied. We also derive the formula to allow for the gain calculation of harmonic lasing. The gain in this formula can be cast in the form of a product of two factors with one of them only depends on the harmonic number, undulator period, and gap. Thus this factor can be used to show that it is favorable to use harmonic lasing to achieve hard x-ray FEL working in the medium energy range and in the small-signal low gain regime.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB040  
About • paper received ※ 09 May 2021       paper accepted ※ 26 May 2021       issue date ※ 10 August 2021  
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MOPAB056 Optimization of a TBA with Stable Optics and Minimal Longitudinal Dispersion and CSR-Induced Emittance Growth emittance, bunching, synchrotron, quadrupole 241
 
  • C. Zhang, Y. Jiao
    IHEP, Beijing, People’s Republic of China
  • C.-Y. Tsai
    HUST, Wuhan, People’s Republic of China
  
  Funding: National Natural Science Foundation of China (No. 11922512), Youth Innovation Promotion Association of Chinese Academy of Sciences (No. Y201904), National Key R&D Program of China (No. 2016YFA0401900)
In the beam transfer line which often consists of dipoles to deflect the beam trajectory, longitudinal dispersion effect and emission of coherent synchrotron radiation (CSR) will lead to beam phase space distortion, thus degrading the machine performance. In this study, optimizations of a triple-bend achromat (TBA) cell are conducted using the multi-objective particle swarm optimization (MOPSO) method to suppress the CSR-induced emittance growth and minimize the longitudinal dispersion functions up to high orders, simultaneously. For the longitudinal dispersion function, results of three optimization settings are reported, which makes the TBA design first-order, second-order, and higher-order isochronous. Furthermore, we study the shortest possible beamline length of the higher-order isochronous TBA design, which may pave the way to designing a more compact beam transfer line. 		 
poster icon Poster MOPAB056 [0.366 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB056  
About • paper received ※ 12 May 2021       paper accepted ※ 28 May 2021       issue date ※ 15 August 2021  
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MOPAB066 Dual Octupole Emittance Growth Correction of the CompactLight XFEL Bunch Compressors octupole, emittance, lattice, linac 272
 
  • R. Auchettl, R.T. Dowd
    AS - ANSTO, Clayton, Australia
  
  An optimized CompactLight X-Ray Free Electron Laser (FEL) bunch compressor design is presented. In this work, we insert an octupole into the center of the two sequential bunch compressors. We show how this scheme can adjust the compression, while correcting the undesirable peak current profile and emittance growth.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB066  
About • paper received ※ 24 May 2021       paper accepted ※ 28 May 2021       issue date ※ 24 August 2021  
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MOPAB097 Two Color Grating design for Soft X-Ray Self-Seeding at LCLS-II electron, simulation, laser, photon 361
 
  • A. Halavanau, D. Cocco, E. Hemsing, G. Marcus, D.S. Morton
    SLAC, Menlo Park, California, USA
  • G.R. Wilcox
    Cornell University, Ithaca, New York, USA
  
  A new grating design is examined for the soft x-ray self-seeding system (SXRSS) at LCLS-II to ultimately produce stable two-color XFEL pulses. The grating performance is analyzed with Fourier optics methods. The final XFEL performance is assessed via full numerical XFEL simulations that substantiate the feasibility of the proposed design.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB097  
About • paper received ※ 19 May 2021       paper accepted ※ 27 July 2021       issue date ※ 21 August 2021  
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MOPAB098 LCLS Multi-Bunch Improvement Plan laser, linac, electron, experiment 365
 
  • A. Halavanau, S. Carbajo, F.-J. Decker, A.K. Krasnykh, A.A. Lutman, A. Marinelli, C.E. Mayes, D.C. Nguyen
    SLAC, Menlo Park, California, USA
  
  Current and future experiments at LCLS require XFEL pulse trains of variable time separation. The cavity based XFEL (CBXFEL) project requires multiple pulses separated by 220 ns, the X-ray Laser Oscillator (XLO) uses 15 ns spaced pulse trains and Matter under Extreme Conditions (MEC) experiments need a shortly spaced (less than 5 ns) pulse trains. In this proceeding, we discuss the LCLS multi-bunch improvement plan and report on its recently status and progress.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB098  
About • paper received ※ 19 May 2021       paper accepted ※ 27 July 2021       issue date ※ 20 August 2021  
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MOPAB099 Intensity Fluctuations Reduction in the Double-Bunch FEL at LCLS electron, laser, free-electron-laser, undulator 369
 
  • G. Zhou, A. Halavanau, C. Pellegrini
    SLAC, Menlo Park, California, USA
  
  In this paper we explore the possibility of reducing the intensity fluctuations of a hard X-ray double-bunch free-electron laser (DBFEL) by using an ultra-short, high peak current electron bunch to generate the seed signal, as studied recently for soft X-ray single bunch self-seeding. The ultra-short, nearly single-spike, SASE pulse is amplified to saturation, where a four-crystal monochromator selects a narrow bandwidth seed for the second bunch. Start-to-end simulation results for 7 keV photon energy are presented here for a DBFEL already studied for LCLS using the HXR undulator. We show that using this enhanced DBFEL (EDBFEL) system; the seed signal intensity fluctuations can be reduced from 85% to about 30%, and the second bunch intensity fluctuation at saturation to about 15%.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB099  
About • paper received ※ 24 May 2021       paper accepted ※ 16 July 2021       issue date ※ 31 August 2021  
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MOPAB100 Progress Report on Population Inversion-Based X-Ray Laser Oscillator laser, electron, experiment, radiation 373
 
  • A. Halavanau, R. Alonso-Mori, A. Aquila, U. Bergmann, D. DePonte, F.-J. Decker, F. Fuller, M. Liang, A.A. Lutman, C. Pellegrini
    SLAC, Menlo Park, California, USA
  • M. Doyle
    UCB, Berkeley, USA
  
  The population inversion X-ray Laser Oscillator (XLO) is a fully coherent, transform limited hard X-ray source. It operates by repetitively pumping inner-shell atomic transitions with an XFEL, in a closed Bragg cavity. XLO will produce very bright monochromatic X-ray pulses for applications in quantum optics, X-ray interferometry and metrology. We report the progress to build the first XLO operating at the copper alpha line, using LCLS 9 keV SASE X-ray pulses as a pump.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB100  
About • paper received ※ 20 May 2021       paper accepted ※ 29 July 2021       issue date ※ 02 September 2021  
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MOPAB150 Optimization of the Gain Medium Delivery System for an X-Ray Laser Oscillator laser, electron, target, free-electron-laser 524
 
  • M. Yadav, N. Majernik, P. Manwani, B. Naranjo, C. Pellegrini, J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • E.C. Galtier, A. Halavanau, C. Pellegrini
    SLAC, Menlo Park, California, USA
  • A. Malinouski
    ASC HMTI, Minsk, Belarus
  
  Funding: This work was supported by DE-SC0009914.
X-ray laser oscillator, dubbed XLO, is a recently proposed project at SLAC to build the first population inversion X-ray laser. XLO utilizes a train of XFEL SASE pulses to pump atomic core-states. The resulting amplified spontaneous emission radiation is recirculated in a backscattering Bragg cavity and subsequently amplified. XLO could provide fully coherent, transform-limited X-ray pulses with 50 meV bandwidth and 1e10 photons. Currently, XLO is being considered for operation at the copper K-alpha line at 8048 eV. In this work, we focus on the optimization of gain medium delivery in the XLO cavity. We consider a fast, subsonic jet of copper nitrate solution, moving through a cylindrical nozzle. We focus on the nozzle geometry optimization and possible diagnostics of the jet-XFEL interaction point. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB150  
About • paper received ※ 24 May 2021       paper accepted ※ 18 June 2021       issue date ※ 27 August 2021  
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MOPAB215 Using ICA for Retrieving Teng Parameters GUI, coupling, factory, optics 711
 
  • A. Lauterbach
    IAP, Frankfurt am Main, Germany
  • G. Franchetti
    GSI, Darmstadt, Germany
  
  The blind source separation (BSS) method of Independent Component Analysis (ICA) is explored as a new approach for the reconstruction of the transfer matrix of Linear Coupling Parameterization. ICA is a method to detangle independent signals out of several measurements of their mixtures. In BSS-calculations, it is usually not possible to retrieve the mixing matrix, for the source signals, as well as the matrix, are unknown. Combining the parameterization model of D.A. Edwards and L.C. Teng with the standard ICA approach, it is though possible to retrieve the mixing matrix, as the form of the original uncoupled motion is known. At the same time arises the possibility to recalculate the parameters of Edwards and Teng through a system of equations of the one turn map components. It can be shown as a proof of concept, that the parameters can be reconstructed up to high accuracy for a simulated, non-perturbed signal.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB215  
About • paper received ※ 10 May 2021       paper accepted ※ 31 May 2021       issue date ※ 23 August 2021  
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MOPAB266 Start-to-End Study on Laser and RF Jitter Effects for MAX-IV SXL laser, radiation, linac, simulation 844
 
  • S.P. Pirani, B.S. Kyle
    MAX IV Laboratory, Lund University, Lund, Sweden
  • F. Curbis, M.A. Pop, S. Werin
    Lund University, Lund, Sweden
  • W. Qin
    DESY, Hamburg, Germany
  
  A Soft X-ray free electron laser (FEL) for the MAX IV Laboratory is currently in the design phase and it will use the existing 3 GeV linac. Present stability limits in the RF and the photocathode laser will affect the performance of the FEL. One of the critical elements for the design of a FEL is to have an estimation on jitter effects of the accelerator parameters on the X-ray radiation. In this regard, we implemented a start-to-end study using Astra, Elegant and Genesis in order to assess possible variations in pulse energy, photon pulse length and spectral width in the Soft X-ray Laser (SXL) radiation. This investigation provides insights on the final SXL performance variation due to RF and laser related jitter affecting the electron beam.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB266  
About • paper received ※ 19 May 2021       paper accepted ※ 26 July 2021       issue date ※ 24 August 2021  
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MOPAB278 Prototype of the Bunch Arrival Time Monitor for SHINE pick-up, laser, electron, controls 881
 
  • X.Q. Liu, L.W. Lai
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • Y.B. Leng, R.X. Yuan, N. Zhang, Y.M. Zhou
    SSRF, Shanghai, People’s Republic of China
  
  Funding: Youth Innovation Promotion Association, CAS (Grant No. 2019290)
Bunch arrival time monitor (BAM) is an important tool to investigate the temporal characteristic of electron bunch in free electron lasers (FEL). Since the timing jitter of electron bunch will affect the FEL’s stability and the resolution of time-resolved experiment at FELs, it is nec-essary to precisely measure the electron bunch’s arrival time information to stabilize the electron bunch’s timing jitter using beam-based feedback. The BAM based on electro-optic modulator (EOM) is currently being devel-oping for Shanghai high-repetition-rate XFEL and Ex-treme light facility (SHINE). And the first BAM prototype has been installed on SXFEL for beam test. The beam test result shows that the estimated resolution of the pro-totype is about 27.5 fs rms. 		 
poster icon Poster MOPAB278 [1.166 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB278  
About • paper received ※ 20 May 2021       paper accepted ※ 23 June 2021       issue date ※ 30 August 2021  
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MOPAB281 Research on Resolution Evaluation of Stripline BPM at SXFEL-UF network, electron, linac, experiment 892
 
  • B. Gao, J. Chen, Y.B. Leng
    SSRF, Shanghai, People’s Republic of China
  
  48 stripline BPMs are installed in the injection section and linear acceleration section of Shanghai X-ray Free Electron Laser (SXFEL) for electron beam position measurement. These two sections require resolution of 20 µm@100pC. Resolution evaluation is an important step in BPM installation and commissioning. This paper presents BPM resolution evaluation methods based on correlation analysis. Experimental methods, data processing and result analysis will be discussed  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB281  
About • paper received ※ 19 May 2021       paper accepted ※ 27 May 2021       issue date ※ 02 September 2021  
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TUPAB046 Preliminary design of the Full Energy Linac Injector for the Southern Advanced Photon Source linac, gun, injection, photon 1454
 
  • X. Liu
    Institute of High Energy Physics, CAS, Guangdong, People’s Republic of China
  • Y. Jiao, B. Li, S. Wang
    IHEP, Beijing, People’s Republic of China
  
  A 4th generation mid-energy range diffraction limited storage ring, named as the Southern Advanced Photon Source (SAPS), is under consideration to be built at the same campus as China Spallation Neutron Source (CSNS), providing a charming one-stop solution for fundamental sciences and industrial applications. While the design of the ring is still under study, a full energy Linac has been proposed as one candidate option for its injector, with the capability of being used as an X-ray Free Electron Laser (XFEL) in the near future. In this paper, an overview of the preliminary design of the Linac is given and simulation results are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB046  
About • paper received ※ 18 May 2021       paper accepted ※ 10 June 2021       issue date ※ 10 August 2021  
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TUPAB064 Specifications and Performance of a Chicane Magnet for the cERL IR-FEL undulator, dipole, operation, operational-performance 1512
 
  • N. Nakamura, K. Harada, N. Higashi, Y. Honda, R. Kato, C. Mitsuda, S. Nagahashi, T. Obina, H. Sakai, M. Shimada, H. Takaki, O.A. Tanaka
    KEK, Ibaraki, Japan
  • Y. Lu
    Sokendai, Ibaraki, Japan
  
  Funding: Work supported by NEDO project "Development of advanced laser processing with intelligence based high-brightness and high-efficiency laser technologies (TACMI project)".
The IR-FEL was constructed in the Compact ERL (cERL) at KEK from October 2019 to May 2020 for the purpose of developing high-power mid-infrared lasers for high-efficiency laser processing utilizing molecular vibrational absorption. The chicane magnet was newly installed between two IR-FEL undulators in the cERL in order to increase the FEL gain and pulse energy by converting the energy modulation to the density modulation in an electron bunch. It consists of three dipole magnets with laminated yokes made of 0.1-mm-thick permalloy sheets and the coil currents of the three magnets are independently controlled by three power supplies with the maximum current of 10 A. The maximum closed orbit bump made by the chicane magnetic field has the longitudinal dispersion(R56) of -6 mm. The coil-current ratio of the three dipole magnets was tuned after installation to make its orbit bumps closed and then the chicane magnet was used in the FEL operation. We present specifications and operational performance of the chicane magnet. 		 
poster icon Poster TUPAB064 [4.053 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB064  
About • paper received ※ 18 May 2021       paper accepted ※ 25 May 2021       issue date ※ 25 August 2021  
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TUPAB067 Production of 120 MeV Gamma-ray Beams at Duke FEL and HIGS Facility operation, wiggler, radiation, diagnostics 1522
 
  • S.F. Mikhailov, V. Popov, G. Swift, P.W. Wallace, Y.K. Wu, J. Yan
    FEL/Duke University, Durham, North Carolina, USA
  • M.W. Ahmed, M. Sikora
    TUNL, Durham, North Carolina, USA
  • H. Ehlers, L.O. Jensen, L. Kochanneck
    Laser Zentrum Hannover, Hannover, Germany
  
  Funding: This work is supported by the US DoE grant #DE-FG02-97ER41033
In this paper we report extension of the operational energy of the gamma ray beams produced at Duke High Intensity Gamma-ray Source (HIGS) up to ~120MeV, opening up a new high energy region of gamma rays for photonuclear physics research. This achievement is based upon development of radiation robust, thermally stable, high-reflectivity fluoride (LaF3/MgF2) multilayer VUV FEL mirrors, enabling us to maintain stable high intensity FEL lasing at the wavelengths of around 175nm. We discuss the challenges of HIGS operation at high gamma and high electron beam energies with the downstream FEL mirror exposed to extremely hush radiation. The experience of the first HIGS user operation with high intensity, high gamma-ray beam energies (85 and ~120MeV) using these new mirrors is also discussed. 		 
poster icon Poster TUPAB067 [1.023 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB067  
About • paper received ※ 30 May 2021       paper accepted ※ 09 June 2021       issue date ※ 31 August 2021  
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TUPAB071 Beam Line Design and Instrumentation for THz@PITZ - the Proof-of-Principle Experiment on a THz SASE FEL at the PITZ Facility undulator, radiation, electron, experiment 1528
 
  • T. Weilbach, P. Boonpornprasert, G.Z. Georgiev, G. Koss, M. Krasilnikov, X. Li, A. Lueangaramwong, F. Mueller, A. Oppelt, S. Philipp, F. Stephan, L.V. Vu
    DESY Zeuthen, Zeuthen, Germany
  • H. Shaker
    CLS, Saskatoon, Saskatchewan, Canada
  
  In order to allow THz pump-X-ray probe experiments at full bunch repetition rate for users at the European XFEL, the Photo Injector Test Facility at DESY in Zeuthen (PITZ) is building a prototype of an accelerator-based THz source. The goal is to generate THz SASE FEL radiation with a mJ energy level per bunch using an LCLS-I undulator driven by the electron beam from PITZ. Therefore, the existing PITZ beam line is extended into a tunnel annex downstream of the existing accelerator tunnel. The beam line extension in the PITZ tunnel consists of three quadrupole magnets, a bunch compressor, a collimation system and a beam dump. In the second tunnel a dipole magnet allows to serve two beam lines, one of them the THz@PITZ beam line. It consists of one LCLS-I undulator for the production of the THz radiation, a quadrupole triplet in front of it and a quadrupole doublet behind it. For the electron beam diagnostic six new screen stations are built, three of them also allow for the observation of the THz radiation for measurements. In addition six BPMs and a new BLM system for machine protection and FEL gain curve measurement will be installed. The progress of this work will be presented.  
poster icon Poster TUPAB071 [1.978 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB071  
About • paper received ※ 18 May 2021       paper accepted ※ 14 June 2021       issue date ※ 13 August 2021  
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TUPAB072 The Status of a Grating Monochromator for Soft X-Ray Self-Seeding Experiment at SHINE electron, laser, free-electron-laser, cavity 1532
 
  • K.Q. Zhang
    SSRF, Shanghai, People’s Republic of China
  • H.X. Deng, C. Feng, B. Liu, T. Liu
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  
  The research status of a grating monochromator for soft X-ray self-seeding experiment at SHINE has been presented in this paper. The monochromator system includes the vacuum cavity, optical elements, and mechanical movement devices. Until now, the vacuum cavity has finished the manufactured process completely, the optical mirrors have finished machining and measured by the longitudinal trace profiler (LTP) and atomic force microscope (AFM). To make sure the monochromator system can achieve an optical resolution of 1/10000 at the photon energy of 700-1300eV, the system has been integrated and tested recently. In this year, the previous online experiment will be performed in the shanghai soft X-ray free-electron laser (FEL) user facility.  
poster icon Poster TUPAB072 [0.717 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB072  
About • paper received ※ 11 May 2021       paper accepted ※ 09 June 2021       issue date ※ 01 September 2021  
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TUPAB073 The Design of EEHG Cascaded Harmonic Lasing for SXFEL User Facility undulator, electron, laser, radiation 1536
 
  • K.Q. Zhang, C. Feng
    SSRF, Shanghai, People’s Republic of China
  • H.X. Deng, B. Liu, T. Liu
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  
  The preliminary design and simulation results of EEHG cascaded harmonic lasing for the SXFEL user facility have been presented in this paper. Using the basic seeded beamline of the SXFEL user facility, the designed parameters are optimized to obtain full coherent FEL output at the 90th harmonic of a 265 nm seed laser. According to the designed parameters and the layout of the SXFEL user facility, the detailed simulations are carried out, the results show that the seeded beamline of the SXFEL user facility can generate 2.93 nm full coherent radiation by the proposed method, which indicates that the method can extend the photon energy range of a seeded FEL and the method can be achieved at the SXFEL user facility.  
poster icon Poster TUPAB073 [0.955 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB073  
About • paper received ※ 11 May 2021       paper accepted ※ 10 June 2021       issue date ※ 27 August 2021  
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TUPAB074 S-Band Transverse Deflecting Structure Design for CompactLight klystron, cavity, operation, impedance 1540
 
  • X.W. Wu, W. Wuensch
    CERN, Meyrin, Switzerland
  • S. Di Mitri
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • N. Thompson
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  The CompactLight project is currently developing the design of a next generation hard X-ray FEL facility, which is based on high-gradient X-band (12 GHz) structures. However, to carry out pump-and-probe experiments in the project, two-bunch operation with a spacing of 10 X-band rf cycles is proposed. A sub-harmonic transverse deflecting structure working at S-band is proposed to direct the two bunches into two separate FEL lines. The two FEL pulses will have independently tunable wavelengths and can be combined in a single experiment with a temporal delay between pulses of ± 100 fs. The rf design of the transverse deflector is presented in this paper.  
poster icon Poster TUPAB074 [1.557 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB074  
About • paper received ※ 19 May 2021       paper accepted ※ 10 June 2021       issue date ※ 21 August 2021  
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TUPAB078 Relative Timing Jitter Effects on Two-stage Seeded FEL at SHINE laser, electron, timing, radiation 1551
 
  • H.X. Yang
    SINAP, Shanghai, People’s Republic of China
  • H.X. Deng, B. Liu, D. Wang, K.S. Zhou
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  
  Funding: The National Key Research and Development Program of China (Grants No. 2016YFA0401901, No. 2018YFE0103100) and the National Natural Science Foundation of China (Grants No. 11935020, No. 11775293).
The synchronization between the ultrashort electron beam and external seed laser is essential for seeded FELs, especially for a multi-stage one. In this paper, we demonstrate a simple method to obtain the correlations between the pulse energy and relative timing jitter for evaluating the corresponding effects. In this method, the sensitivity of the output FEL performance against electron beam properties is demonstrated by scanning the electron beam and seed lasers, and the fitted curve is used to predict the pulse energy in different timing jitter by random sampling. The results indicate that the pulse energy of the first-stage EEHG is more stable than the second-stage HGHG. Meanwhile, the rise of bunch charge from 100 pC to 300 pC can reduce the timing control requirement by a factor of least 3 for the RMS timing jitter in our numerical simulations based on the parameters of Shanghai High-Repetition-Rate XFEL and Extreme Light Facility. The timing jitter study can demonstrate the feasibility of the EEHG-HGHG cascading scheme in different current profiles for generating Fourier-transform-limited soft X-ray FEL. 		 
poster icon Poster TUPAB078 [0.866 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB078  
About • paper received ※ 11 May 2021       paper accepted ※ 11 June 2021       issue date ※ 21 August 2021  
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TUPAB079 Using ER@CEBAF to Show that a Multipass ERL Can Drive an XFEL operation, controls, electron, acceleration 1555
 
  • G. Perez-Segurana
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • I.R. Bailey, P.H. Williams
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • I.R. Bailey
    Lancaster University, Lancaster, United Kingdom
  • R.M. Bodenstein, S.A. Bogacz, D. Douglas, Y. Roblin, T. Satogata
    JLab, Newport News, Virginia, USA
  • T. Satogata
    ODU, Norfolk, Virginia, USA
  • P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  A multi-pass recirculating superconducting CW linac offers a cost effective path to a multi-user facility with unprecedented scientific and industrial reach over a wide range of disciplines. We propose such a facility as an option for a potential UK-XFEL. Energy Recovery enables multi-MHz FEL sources, for example, an X-ray FEL oscillator or regenerative amplifier FEL. Additionally, combining with external lasers and/or self-interaction would provide access to MeV and GeV gamma-rays via inverse Compton scattering at high average power for nuclear and particle physics applications. An opportunity exists to demonstrate the necessary point-to-parallel longitudinal matches to drive an XFEL and successfully energy recover at the upcoming 5-pass up, 5-pass down Energy Recovery experiment on CEBAF at JLab termed ER@CEBAF. We show candidate matches and simulations supporting the minimal necessary modifications to CEBAF this will require. This includes linearisation of the longitudinal phase space in the injector and a reduction in the dispersion of the arcs, both of which increase the energy acceptance of CEBAF. We expect to commence initial tests of these adaptations on CEBAF during 2021.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB079  
About • paper received ※ 17 May 2021       paper accepted ※ 27 July 2021       issue date ※ 17 August 2021  
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TUPAB080 Design and Status of the Beam Switchyard of the Shanghai Soft X-Ray FEL User Facility electron, kicker, undulator, linac 1559
 
  • S. Chen, R. Wang
    SSRF, Shanghai, People’s Republic of China
  • H.X. Deng, C. Feng, X. Fu, B. Liu
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  
  SXFEL-UF, a soft X-ray FEL user facility located in Shanghai, has been upgraded from the existing test facility. Electron energy increases from 840 MeV to 1.5 GeV and a SASE FEL line will be added besides the existing seeding FEL line. It has started commissioning since early this year. In order for simultaneous operation of the two FEL lines, a beam switchyard is built between the linac and the two FEL lines. In this paper, the physics design of the beam switchyard is described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB080  
About • paper received ※ 19 May 2021       paper accepted ※ 11 June 2021       issue date ※ 20 August 2021  
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TUPAB082 Analysis of the Effect of Energy Chirp in Implementing EEHG at SXL bunching, electron, simulation, linac 1566
 
  • M.A. Pop, F. Curbis, B.S. Kyle, S.P. Pirani, W. Qin, S. Werin
    MAX IV Laboratory, Lund University, Lund, Sweden
  • F. Curbis, S. Werin
    Lund University, Lund, Sweden
  • W. Qin
    DESY, Hamburg, Germany
  
  As a part of the efforts to improve the longitudinal coherence in the design of the Soft X-ray FEL (the SXL) at MAX IV, we present a possible implementation of the EEHG harmonic seeding scheme partly integrated into the second bunch compressor of the existing LINAC. A special focus is given to the effect of CSR on the resulting EEHG bunching and on how this unwanted effect might be controlled.  
poster icon Poster TUPAB082 [1.825 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB082  
About • paper received ※ 15 May 2021       paper accepted ※ 28 July 2021       issue date ※ 17 August 2021  
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TUPAB084 An Empirically-Derived ABCD Matrix for Transverse Dynamics Studies in Seeded Free-Electron Lasers radiation, electron, laser, free-electron-laser 1573
 
  • R. Robles
    Stanford University, Stanford, California, USA
  • Z. Huang, G. Marcus
    SLAC, Menlo Park, California, USA
  
  Funding: DOE Contract DE-AC02-76SF00515.
We present a simple empirical method for deriving an ABCD matrix for studying the transverse dynamics of the radiation field in seeded, high-gain free-electron lasers before saturation. In spite of the inherently nonlinear nature of FEL optical guiding, the ABCD matrix we find is able to predict the evolution of the FEL mode size and centroid to a high degree of accuracy across a large range of input mode characteristics. This scheme enables extremely fast simulation of transverse dynamics, which in turn greatly simplifies numerical studies of seeded FEL systems. Of particular interest in that regard is the x-ray regenerative amplifier free-electron laser, in which the x-ray beam propagates through an optical cavity many hundreds of times, thereby making traditional simulation methods cumbersome and time consuming. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB084  
About • paper received ※ 19 May 2021       paper accepted ※ 21 June 2021       issue date ※ 11 August 2021  
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TUPAB085 Three-Dimensional Radiative Effects in the Compression of Ultra-Short Electron Micro-Bunches emittance, electron, laser, simulation 1577
 
  • R. Robles, J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • S.B. van der Geer
    Pulsar Physics, Eindhoven, The Netherlands
  
  Funding: DOE Contract DE-SC0009914 DOE Contract DE-SC0020409 National Science Foundation Grant No. PHY-1549132
Micro-bunched current profiles have recently gained traction as an alternative to bulk compression in certain free-electron laser applications. The attraction of the micro-bunched structure is owed in part to its promise to minimize deleterious effects associated with coherent synchrotron radiation during compression. Simultaneously, these profiles push the boundaries of traditional one-dimensional CSR simulation models which assume the bunch length to far exceed the transverse beam size in the bunch rest frame - an assumption which may be violated by the sub-micron length micro-bunches. Here we present simulation studies of the impact of three-dimensional CSR effects on micro-bunching based compression schemes using the General Particle Tracer code. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB085  
About • paper received ※ 19 May 2021       paper accepted ※ 23 June 2021       issue date ※ 13 August 2021  
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TUPAB086 FLASH2020+ Plans for a New Coherent Source at DESY laser, electron, experiment, undulator 1581
 
  • E. Allaria, N. Baboi, K. Baev, M. Beye, G. Brenner, F. Christie, C. Gerth, I. Hartl, K. Honkavaara, B. Manschwetus, J. Mueller-Dieckmann, R. Pan, E. Plönjes-Palm, O. Rasmussen, J. Rönsch-Schulenburg, L. Schaper, E. Schneidmiller, S. Schreiber, K.I. Tiedtke, M. Tischer, S. Toleikis, R. Treusch, M. Vogt, L. Winkelmann, M.V. Yurkov, J. Zemella
    DESY, Hamburg, Germany
  
  With FLASH2020+, a major upgrade of the FLASH facility has started to meet the new requirements of the growing soft-x ray user community. The design of the FEL beamlines aims at photon properties suitable to the needs of future user experiments with high repetition rate XUV and soft X-ray radiation. By the end of the project, both existing FEL lines at FLASH will be equipped with fully tunable undulators capable of delivering photon pulses with variable polarization. The use of the external seeding at 1 MHz in burst mode is part of the design of the new FLASH1 beamline, while FLASH2 will exploit novel lasing concepts based on different undulator configurations. The new FLASH2020+ will rely on an electron beam energy of 1.35 GeV that will extend the accessible wavelength range to the oxygen K-edge with variable polarization. The facility will be completed with new laser sources for pump and probe experiment and new experimental stations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB086  
About • paper received ※ 19 May 2021       paper accepted ※ 27 May 2021       issue date ※ 23 August 2021  
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TUPAB089 Proof-of-Principle Experiment Design for PEHG-FEL in SXFEL User Facility laser, electron, radiation, experiment 1589
 
  • Z. Qi, H.X. Deng, C. Feng, B. Liu
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • S. Chen, Z.T. Zhao
    SSRF, Shanghai, People’s Republic of China
  
  In this paper, we demonstrate a proof-of-principle experimental design for phase-merging enhanced harmonic generation (PEHG) free electron laser (FEL) in Shanghai Soft X-ray Free Electron Laser (SXFEL) user facility. The simulation results indicate that, taking advantage of the beam switchyard, the normal modulator and the seeded FEL line in SXFEL user facility, together with an oblique incident seed laser, we can perform the phase-merging effect in PEHG and finally get an 8.86nm FEL radiation through the undulator, which is the 30th harmonic of the seed laser.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB089  
About • paper received ※ 19 May 2021       paper accepted ※ 17 June 2021       issue date ※ 02 September 2021  
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TUPAB092 Demonstration FELs Using UC-XFEL Technologies at the SAMURAI Laboratory undulator, cryogenics, electron, laser 1592
 
  • N. Majernik, G. Andonian, O. Camacho, A. Fukasawa, G.E. Lawler, W.J. Lynn, B. Naranjo, J.B. Rosenzweig, Y. Sakai, O. Williams
    UCLA, Los Angeles, California, USA
  • R. Robles
    SLAC, Menlo Park, California, USA
  
  Funding: DOE HEP Grant DE-SC0020409, National Science Foundation Grant No. PHY-1549132
The ultra-compact x-ray free-electron laser (UC-XFEL), described in [J. B. Rosenzweig, et al. 2020 New J. Phys. 22 093067], combines several cutting edge beam physics techniques and technologies to realize an x-ray free electron laser at a fraction of the cost and footprint of existing XFEL installations. These elements include cryogenic, normally conducting RF structures for both the gun and linac, IFEL bunch compression, and short-period undulators. In this work, several stepping-stone, demonstrator scenarios under discussion for the UCLA SAMURAI Laboratory are detailed and simulated, employing different subsets of these elements. The cost, footprint, and technology risk for these scenarios are considered in addition to the anticipated engineering and physics experience gained. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB092  
About • paper received ※ 19 May 2021       paper accepted ※ 11 August 2021       issue date ※ 02 September 2021  
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TUPAB099 Construction of an Infrared FEL at the Compact ERL undulator, laser, operation, electron 1608
 
  • R. Kato, M. Adachi, S. Eguchi, K. Harada, N. Higashi, Y. Honda, T. Miyajima, S. Nagahashi, N. Nakamura, K.N. Nigorikawa, T. Nogami, T. Obina, H. Sagehashi, H. Sakai, M. Shimada, T. Shioya, M. Tadano, R. Takai, O.A. Tanaka, Y. Tanimoto, K. Tsuchiya, T. Uchiyama, A. Ueda, M. Yamamoto
    KEK, Ibaraki, Japan
  • R. Hajima
    QST, Tokai, Japan
  • N.P. Norvell
    SLAC, Menlo Park, California, USA
  • F. Sakamoto
    Akita National College of Technology, Akita, Japan
  • M. Shimada
    HSRC, Higashi-Hiroshima, Japan
  
  Funding: Work supported by NEDO project "Development of advanced laser processing with intelligence based high-brightness and high-efficiency laser technologies (TACMI project)".
The compact Energy Recovery Linac (cERL) has been in operation at KEK since 2013 to demonstrate ERL performance and develop ERL technology. Recently KEK has launched an infrared FEL project with a competitive funding. The purpose of this project is to build a mid-infrared FEL at the cERL, and to use that FEL as a light source for construction of the processing database required for industrial lasers. The FEL system is composed of two 3-m undulators and a matching section between them, and generates light with a maximum pulse energy of 0.1 micro-J at the wavelength of 20 microns with an 81.25 MHz repetition rate. The FEL is also expected to become a proof-of-concept machine for ERL base FELs for future EUV lithography. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB099  
About • paper received ※ 20 May 2021       paper accepted ※ 14 June 2021       issue date ※ 29 August 2021  
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TUPAB100 FEL Design Elements of SABINA: A Free Electron Laser For THz-MIR Polarized Radiation Emission undulator, radiation, electron, simulation 1612
 
  • F. Dipace, E. Chiadroni, M. Ferrario, A. Ghigo, L. Giannessi, A. Giribono, L. Sabbatini, C. Vaccarezza
    INFN/LNF, Frascati, Italy
  • A. Doria, A. Petralia
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • S. Lupi
    Sapienza University of Rome, Roma, Italy
  • S. Macis
    La Sapienza University of Rome, Rome, Italy
  • V. Petrillo
    Universita’ degli Studi di Milano, Milano, Italy
  • V. Petrillo
    INFN-Milano, Milano, Italy
  
  Funding: SABINA is a project co-funded by Regione Lazio within POR-FESR 2014-2020 program.
SABINA, acronym of "Source of Advanced Beam Imaging for Novel Applications", will be a Self-Amplified Spontaneous Emission Free Electron Laser (SASE FEL) providing a wide spectral range (from THz to MIR) of intense, short and variable polarization pulses for investigation in physics, chemistry, biology, cultural heritage, and material science. In order to reach these goals high brightness electron beams within a 30-100 MeV energy range, produced at SPARC photo-injector, will be transported up to an APPLE-X undulator through a dogleg. Space charge effects and Coherent Synchrotron Radiation (CSR) effects must be held under control to preserve beam quality. Studies on beam transport along the undulator and of the properties of the radiation field have been performed with "Genesis 1.3" simulation code. A downstream THz optics photon delivery system has also been designed to transport radiation on the long path from the undulator exit up to user experimental area. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB100  
About • paper received ※ 19 May 2021       paper accepted ※ 11 June 2021       issue date ※ 02 September 2021  
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TUPAB102 A New 2nd Bunch Compression Chicane for the FLASH2020+ Project quadrupole, dipole, vacuum, focusing 1618
 
  • M. Vogt, J. Zemella
    DESY, Hamburg, Germany
  
  The first stage of the FLASH2020+ project is an upgrade of the FLASH injector beamline. Within this framework, the 2nd bunch compression chicane (BCC) will be completely redesigned. The old S-chicane will be replaced with a new C-chicane which is 3.5m shorter thereby generating space a new section for re-matching the beam from the injector into the linac. The new BCC will be equipped with quad/skew-quad units in both legs of the chicane to compensate correlations of the transverse degrees of freedom with the longitudinal ones. Since quadrupoles tend to have a circular bore, the chicane is designed with movable round vacuum chambers and movable dipoles for maintaining full flexibility in choosing the compression parameters. This article describes the technical details and introduces a thin-lens model of BCCs which allows analytical estimates on the effects of powering the quad/skew-quad units on optics parameters as well as estimates on the required strengths of these magnets in order to remove correlations of the magnitudes typically observed at FLASH.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB102  
About • paper received ※ 19 May 2021       paper accepted ※ 14 June 2021       issue date ※ 29 August 2021  
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TUPAB103 Discussion on CSR instability in EEHG Simulation electron, bunching, laser, simulation 1622
 
  • D. Samoilenko, W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • F. Curbis, M.A. Pop, S. Werin
    MAX IV Laboratory, Lund University, Lund, Sweden
  • P. Niknejadi, G. Paraskaki
    DESY, Hamburg, Germany
  • F. Pannek
    University of Hamburg, Hamburg, Germany
  
  Echo-Enabled Harmonic Generation (EEHG) is an external seeding technique for XUV and soft X-ray Free Electron Lasers (FEL). It has recently been experimentally demonstrated and currently many facilities worldwide intend to incorporate it in user operation. The EEHG process relies on very accurate and complex transformations of electron beam phase space by means of a series of undulators coupled to lasers and dispersive chicanes. As a result of the phase space manipulation, electrons are bunched at a high harmonic of the seed laser wavelength allowing coherent emission at few nm wavelength. Dispersion occurring in strong chicanes is imperative for implementation of this scheme and effective electron bunching generation. However, strong chicanes at the same time can be source of beam instability effects, such as Coherent Synchrotron Radiation (CSR), that can significantly grow in these conditions and suppress the bunching process. Therefore, there is a common need to investigate such effects in detail. Here, we discuss their treatment with simulation codes applied to a typical EEHG setup.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB103  
About • paper received ※ 19 May 2021       paper accepted ※ 17 June 2021       issue date ※ 12 August 2021  
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TUPAB107 Accelerator and Light Source Research Program at Duke University polarization, storage-ring, undulator, electron 1636
 
  • Y.K. Wu
    FEL/Duke University, Durham, North Carolina, USA
  
  Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
The accelerator and light source research program at Duke Free-Electron Laser Laboratory (DFELL), TUNL, is focused on the development of the storage ring based free-electron lasers (FELs) and a state-of-the-art Compton gamma-ray source, the High Intensity Gamma-ray Source (HIGS) driven by the storage ring FEL. With a maximum total flux of about 3·1010 gamma/s and a spectral flux of more than 1,000 gamma/s/eV around 10 MeV, the HIGS is the world’s highest-flux Compton gamma-ray source. Operated in the energy range from 1 to 100 MeV, the HIGS is a premier Compton gamma-ray facility in the world for a variety of nuclear physics research programs, both fundamental and applied. In this work, we will describe our recent light source development to enable the production of gamma rays in the higher energy range from 100 and 120 MeV. We will also provide a summary of our recent accelerator physics and FEL physics research activities. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB107  
About • paper received ※ 26 May 2021       paper accepted ※ 14 July 2021       issue date ※ 15 August 2021  
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TUPAB109 Characterization of the X-Ray Angular Pointing Jitter in the LCLS Hard X-ray Undulator Line undulator, electron, cavity, detector 1640
 
  • R.A. Margraf, Z. Huang, J.P. MacArthur, G. Marcus, T. Sato, D. Zhu
    SLAC, Menlo Park, California, USA
  • Z. Huang
    Stanford University, Stanford, California, USA
  
  Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
The angular pointing jitter of X-ray pulses produced by an X-ray Free-Electron Laser (XFEL) depends on both intrinsic properties of the SASE (Self-amplified spontaneous emission) process and jitters in beamline variables such as electron orbit. This jitter is of interest to the Cavity-Based XFEL (CBXFEL)* project at SLAC, which will lase seven undulators inside an X-ray cavity of four diamond Bragg mirrors. The CBXFEL cavity has a narrow angular bandwidth, thus large angular jitters cause X-rays to leak out of the cavity and degrade cavity efficiency. To understand contributors to angular pointing jitter, we studied the pointing jitter of the Linac Coherent Light Source (LCLS) Hard X-ray Undulator line (HXU). Monochromatic and pink X-rays were characterized at the X-ray Pump Probe (XPP) instrument. We found pulses with high monochromatized pulse energy and small electron beam orbit in the undulator have the lowest angular pointing jitter. We present here our measurement results, discuss why these factors correlate with pointing stability, and propose a strategy for CBXFEL to reduce angular pointing jitter and account for angular pointing jitter in cavity efficiency measurements.
*Gabriel Marcus et al. "CBXFEL Physics Requirements Document for the Optical cavity Based X-Ray Free Electron Lasers Research and Development Project." SLAC-I-120-103-121-00. Apr 2020. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB109  
About • paper received ※ 19 May 2021       paper accepted ※ 14 June 2021       issue date ※ 14 August 2021  
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TUPAB110 Measurement and Correction of RF Kicks in the LCLS Accelerator to Improve Two-Bunch Operation electron, klystron, cavity, experiment 1644
 
  • R.A. Margraf, F.-J. Decker, Z. Huang, G. Marcus
    SLAC, Menlo Park, California, USA
  • Z. Huang
    Stanford University, Stanford, California, USA
  
  Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
RF kicks, caused by a misalignment of an electron beam and acceleration structure, produce an electron orbit in the accelerator which decreases the final energy of the accelerated electron beam and is detrimental to lasing electron bunches in an X-ray Free Electron Laser (XFEL). RF kicks can depend on the RF waveform of the accelerating structure, so controlling this effect is particularly important when two or more electron bunches are accelerated within an RF fill time. Multibunch modes have been successfully developed for the Linac Coherent Light Source (LCLS) accelerator at SLAC,* and are being continually improved to accommodate new experiments. One such experiment, the Cavity-Based XFEL (CBXFEL)** project will require two electron bunches separated by 218.5 ns which must be identical in energy and orbit. To reduce variation in energy and orbit between the two bunches, we studied the RF kicks produced by each of 75 accelerator segments in the LCLS linac at several RF timings. Here, we discuss these measurements and propose a method to correct RF kicks in the LCLS accelerator using corrector dipoles and quadrupoles.
* F.-J. Decker, et al. Recent Developments and Plans for Two Bunch Operation, Proc. of FEL2017, TUP023.
** Gabriel Marcus et al. CBXFEL Physics Requirements Document. SLAC-I-120-103-121-00. 2020. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB110  
About • paper received ※ 19 May 2021       paper accepted ※ 15 June 2021       issue date ※ 29 August 2021  
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TUPAB111 Layout of the Laser Heater for FLASH2020+ electron, laser, undulator, free-electron-laser 1647
 
  • C. Gerth, E. Allaria, A. Choudhuri, L. Schaper, E. Schneidmiller, S. Schreiber, M. Tischer, P. Vagin, M. Vogt, L. Winkelmann, M.V. Yurkov, J. Zemella
    DESY, Hamburg, Germany
  
  The major upgrade FLASH2020+ of the FEL user facility FLASH includes an improved injector layout for the generation of the high-brightness electron beam as well as an externally seeded FEL beamline. Microbunching gain of initial modulations or shot-noise fluctuations degrade the electron beam quality, which is in particular harmful to the external seed process. To minimize the microbunching gain by a controlled increase of the uncorrelated energy spread, the installation of a laser heater is foreseen directly upstream of the first bunch compression chicane. In this paper, we present the layout of the laser heater section, which follows the original proposal published almost 20 years ago and differs in several aspects from the common layout implemented at many other FEL facilities. The considerations that have been made for the optimisation of the laser heater parameters are described in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB111  
About • paper received ※ 19 May 2021       paper accepted ※ 07 July 2021       issue date ※ 01 September 2021  
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TUPAB113 Highlights From the Conceptual Design Report of the Soft X-Ray Laser at MAX IV undulator, electron, laser, linac 1651
 
  • F. Curbis, J. Andersson, L. Isaksson, B.S. Kyle, F. Lindau, E. Mansten, H. Tarawneh, P.F. Tavares, S. Thorin, A.S. Vorozhtsov
    MAX IV Laboratory, Lund University, Lund, Sweden
  • S. Bonetti
    Stockholm University, Stockholm, Sweden
  • V.A. Goryashko, P.M. Salén
    Uppsala University, Uppsala, Sweden
  • P. Johnsson, S.P. Pirani, M.A. Pop, W. Qin, S. Werin
    Lund University, Lund, Sweden
  • M. Larsson
    Stockholm University, Department of Physics, Stockholm, Sweden
  • A. Nilsson
    FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
  • J.A. Sellberg
    KTH Physics, Stockholm, Sweden
  
  Funding: Knut and Alice Wallenberg Foundation
The SXL (Soft X-ray Laser) project developed a conceptual design for a soft X-ray Free Electron Laser in the 1–5 nm wavelength range, driven by the existing MAX IV 3 GeV linac. In this contribution we will focus on the FEL operation modes developed for the first phase of the project based on two different linac modes. The design work was supported by the Knut and Alice Wallenberg foundation and by several Swedish universities and organizations (Stockholm, Uppsala, KTH Royal Institute of Technology, Stockholm-Uppsala FEL center, MAX IV laboratory and Lund University). 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB113  
About • paper received ※ 19 May 2021       paper accepted ※ 17 June 2021       issue date ※ 19 August 2021  
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TUPAB114 FEL Performance and Beam Quality Assessment of Undulator Line for the CompactLight Facility. undulator, brilliance, photon, electron 1655
 
  • H.M. Castañeda Cortés, D.J. Dunning, N. Thompson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  Funding: H2020 CompactLight has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 777431
The H2020 CompactLight Project aims for the design of innovative, cost-effective, compact FEL facilities to generate higher peak brilliance radiation in the soft and hard X-ray. In this paper we assess via simulation studies the performance of a variably polarising APPLE-X afterburner positioned downstream of a helical Super Conducting Undulator (SCU). We discuss the optimum balance between the active SCU length and the afterburner length, considering the peak brilliance and pulse energy of the output. Our studies are complemented with analysis of the optical beam quality of the afterburner output to determine the design constraints of the photon beamline that delivers the FEL output to the experimental areas.
* Mak, A., Salen, P., Goryashko, V., Clarke, J., http://uu.diva-portal.org/smash/record.jsf?pid=diva2\%3A1280300&dswid=3236
** Lutman, A. et al. Nature Photonics 10, 468 		 
poster icon Poster TUPAB114 [1.210 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB114  
About • paper received ※ 11 May 2021       paper accepted ※ 10 June 2021       issue date ※ 27 August 2021  
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TUPAB115 Status Report of the Superconducting Free-Electron Laser FLASH at DESY experiment, electron, undulator, operation 1659
 
  • J. Rönsch-Schulenburg, F. Christie, K. Honkavaara, M. Kuhlmann, S. Schreiber, R. Treusch, M. Vogt, J. Zemella
    DESY, Hamburg, Germany
  
  The free-electron laser in Hamburg (FLASH) is a high brilliance XUV and soft X-ray SASE FEL user-facility at DESY. FLASH’s superconducting linac can accelerate several thousand electron bunches per second in 10 Hz bursts of up to 800 µs length. The long bunch trains can be split in two parts and shared between two undulator beamlines. During 2020, FLASH supplied, in standard operation, up to 500 bunches at 10 Hz in two bunch trains with independent fill patterns and compression schemes. The FLASH2 undulator beamline comprises variable gap undulators that allow different novel lasing schemes. A third beamline accommodates the FLASHForward plasma wakefield acceleration experiment. We report on the FLASH operation in 2019 - 2021 and present a few highlights.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB115  
About • paper received ※ 19 May 2021       paper accepted ※ 21 June 2021       issue date ※ 19 August 2021  
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TUPAB117 Eigenmode Decomposition for Free-Electron Lasers Using Bayesian Analysis optics, laser, simulation, distributed 1666
 
  • P. Liu, W. Li, Y.K. Wu, J. Yan
    FEL/Duke University, Durham, North Carolina, USA
  
  Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
Laser beams from an optical cavity, such as free-electron laser (FEL) resonators, are typically a mixture of the cavity’s eigenmodes, such as the Hermite-Gaussian (HG) modes or Laguerre-Gaussian (LG) modes. Robust evaluation of the eigenmode spectrum of a multimode laser beam has various applications in laser development, research, and utilization. In this work, a general eigenmode decomposition method for a multimode laser beam has been developed based on Bayesian analysis. This problem is transformed into a linear system and then solved using a Gaussian probabilistic model. Using Bayesian analysis, prior knowledge about the mode content is further incorporated into the solution to improve the results for laser beams contaminated with complex disturbances. The decomposition of the beam image from the incoherent intensity addition of HG modes is discussed with different types of noise or disturbances. The simulation results have been used to show the robustness of this method. This method can be straightforwardly extended into other cases such as the wavefront decomposition into the coherent superposition of HG and LG modes. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB117  
About • paper received ※ 18 May 2021       paper accepted ※ 15 June 2021       issue date ※ 01 September 2021  
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TUPAB119 Beam Loss Study for the Implementation of Dechirper at the European XFEL undulator, radiation, simulation, electron 1670
 
  • J.J. Guo
    University of Chinese Academy of Sciences, Beijing, People’s Republic of China
  • W. Decking, M.W. Guetg, J.J. Guo, S. Liu, W. Qin, I. Zagorodnov
    DESY, Hamburg, Germany
  • Q. Gu, J.J. Guo
    SINAP, Shanghai, People’s Republic of China
  • Q. Gu
    Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
  
  The European XFEL is a free-electron laser facility based on superconducting linac with high repetition rate up to 4.5 MHz. Wakefield structure (also called dechirper module) is planned to be installed in front of the SASE beam line at the European FEL, which can be used as a kicker for two-color scheme or a dechirper to control the bandwidth of SASE radiation. When the beam pass through the dechirper module, strong longitudinal and transverse wakefields can be excited to introduce a correlated energy chirp and a kick along the bunch. However, due to the relatively small gap of dechirper, beam halo particles hitting the dechirper module can lead to energy deposition and generate additional radiation, which can cause serious damage to the downstream undulators. For this reason, simulations have been performed using BDSIM to define the maximum acceptable beam halo, and the results are presented in this paper.  
poster icon Poster TUPAB119 [1.489 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB119  
About • paper received ※ 16 May 2021       paper accepted ※ 15 June 2021       issue date ※ 12 August 2021  
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TUPAB121 Photoinjector Drive Laser Temporal Shaping for Shanghai Soft X-Ray Free Electron Laser laser, electron, cathode, flattop 1674
 
  • C.L. Li, X.T. Wang, W.Y. Zhang
    Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
  • X.L. Dai
    SSRF, Shanghai, People’s Republic of China
  • H.X. Deng, L. Feng, B. Liu, J.G. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  
  Shanghai soft X ray free electron laser (SXFEL) initial designed shape of the photocathode driver laser is flattop produced by α-BBO stacking. The advantage of this design is attractive in producing electron bunch with low initial emittance and high uniformity along the electron bunch. However, some unavoidable modulations are generated along the laser pulse which trigger the electron bunch modulation generated at the source, which is due to the fast response time (tens of femtosecond) of copper cathode. In order to eliminate the modulation of electron bunch, temporal Gaussian driver laser was designed and tested, measurement results show the electron bunch longitudinal modulation was removed. In this paper, we present two kinds of driver laser pulse temporal shaping methods based on α-BBO stacking and UV grating pair shaping. Moreover, corresponding electron bunch temporal profile are also presented.  
poster icon Poster TUPAB121 [2.469 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB121  
About • paper received ※ 19 May 2021       paper accepted ※ 02 June 2021       issue date ※ 25 August 2021  
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TUPAB122 SASE3 Variable Polarization Project at the European XFEL undulator, polarization, vacuum, electron 1678
 
  • S.K. Karabekyan, S. Abeghyan, M. Bagha-Shanjani, S. Casalbuoni, U. Englisch, G. Geloni, J. Grünert, S. Hauf, C. Holz, D. La Civita, J. Laksman, D. Mamchyk, M.P. Planas, F. Preisskorn, S. Serkez, H. Sinn, A. Violante, G. Wellenreuther, M. Wuenschel, M. Yakopov, C. Youngman
    EuXFEL, Schenefeld, Germany
  • A. Block, W. Decking, N. Golubeva, K. Knebel, T. Ladwig, D.L. Lenz, D. Lipka, R. Mattusch, N. Mildner, E. Negodin, D. Nölle, J. Prenting, F. Saretzki, M. Schlösser, F. Schmidt-Föhre, E. Schneidmiller, D. Thoden, T. Wamsat, S. Wendt, T. Wilksen, T. Wohlenberg, M.V. Yurkov
    DESY, Hamburg, Germany
  • M. Brügger, M. Calvi, S. Danner, R. Ganter, L. Huber, A. Keller, M.S. Schmidt, T. Schmidt
    PSI, Villigen PSI, Switzerland
  • D.E. Kim
    PAL, Pohang, Republic of Korea
  • Y. Li
    IHEP, People’s Republic of China
  
  At the European XFEL, two undulator systems for hard and one for soft X-rays have been successfully put into operation. The SASE3 soft X-ray undulator system generates linearly polarized radiation in the horizontal plane. One of the requirements for extending the radiation characteristics is the ability to obtain different polarization modes. These include both right and left circular, elliptical polarization, or linear polarization at an arbitrary angle. For this purpose, a system consisting of four APPLE X helical undulators developed at the Paul Scherrer Institute (PSI) is used. This paper presents the design parameters of the SASE3 undulator system after modifying it with the helical afterburner. It also describes the methods and the design solutions different from those used at PSI. The status and schedule of the project are introduced.  
poster icon Poster TUPAB122 [0.553 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB122  
About • paper received ※ 19 May 2021       paper accepted ※ 31 May 2021       issue date ※ 27 August 2021  
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TUPAB125 Studies of Particle Losses From the Beam in the EU-XFEL Following Scattering by a Slotted Foil undulator, radiation, simulation, diagnostics 1681
 
  • A.T. Potter, A. Wolski
    The University of Liverpool, Liverpool, United Kingdom
  • W. Decking, S. Liu
    DESY, Hamburg, Germany
  • F. Jackson
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  One technique for producing short radiation pulses in an FEL involves the use of a slotted foil in a bunch compressor. However, the scattering of particles from the foil can lead to increased particle losses and the generation of secondary particles. This is a particular concern for high rep-rate FELs, such as the European XFEL, where there are plans to implement the slotted-foil technique for short pulse generation. The study reported here aims to characterise the impact of a slotted foil in the European XFEL on the radiation dose in the front section of one of the undulators. Simulations were performed using BDSIM: this code tracks primary particles along the beamline, models the interaction between particles and accelerator components and tracks secondary particles produced by these interactions. The results indicate the amount of energy deposited in the front section of one of the FEL undulators, and provide a basis for optimisation of the collimation system to keep the energy deposition and radiation doses within acceptable limits.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB125  
About • paper received ※ 19 May 2021       paper accepted ※ 10 June 2021       issue date ※ 28 August 2021  
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TUPAB126 Spectral Gap in the Middle Infrared FEL Oscillator of FELiCHEM GUI, laser, electron, free-electron-laser 1685
 
  • Y.P. Zhu, H.T. Li, Z. Zhao
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  
  A phenomenon of spectral gap is observed in the Middle Infrared FEL Oscillator of FELiCHEM: the laser power falls down at the particular wavelength. Starting with the experimental data, this paper focuses on the simulation calculation and analysis of the effect from using the partial waveguide. The relationship between waveguide and spectral gap is revealed.  
poster icon Poster TUPAB126 [1.063 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB126  
About • paper received ※ 17 May 2021       paper accepted ※ 14 June 2021       issue date ※ 21 August 2021  
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TUPAB129 Beam Based Alignment in a Compact THz-FEL Facility quadrupole, alignment, linac, undulator 1692
 
  • Q.S. Chen, T. Hu, K.F. Liu, B. Qin, Y.Q. Xiong
    HUST, Wuhan, People’s Republic of China
  
  In this paper, we presented the beam based alignment results in a compact THz-FEL facility. The alignment was divided into two sections, the transport line and the optical line. In the transport line, all the five quadrupoles upstream of the undulator were adjusted one by one to fit the electron beam from the traveling wave linac. In the optical line, a set of auxiliary coils were winded on the yokes of the quadrupole downstream of the double bend achromat (DBA) to produce a vertical steering force. Another combined steering magnet, together with the auxiliary coils, corrected the beam orbit in the optical line. With the dispersion free test, the displacement between the magnetic centers of the quads and the beam orbit was less than 0.1mm.  
poster icon Poster TUPAB129 [0.673 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB129  
About • paper received ※ 18 May 2021       paper accepted ※ 17 June 2021       issue date ※ 27 August 2021  
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TUPAB218 Fully Covariant Two-Particle Space-Charge Dynamics Using the Liénard-Wiechert Potentials electromagnetic-fields, electron, space-charge, dipole 1931
 
  • B.T. Folsom, E. Laface
    ESS, Lund, Sweden
  
  Space charge models typically assume instantaneous propagation of the electromagnetic fields between particles in a bunch, describing forces in the frame of the reference particle. In this paper, we construct a space-charge tracking code from the retarded Liénard-Wiechert potentials, which are covariant by design, in a Lagrangian formulation. Such potentials are manipulated with covariant derivatives to produce the necessary equations of motion that will be solved in a test system of two particles at various relative energies. Magnetic dipole moment dynamics are also evaluated where applicable.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB218  
About • paper received ※ 19 May 2021       paper accepted ※ 19 July 2021       issue date ※ 11 August 2021  
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TUPAB291 Subsystem Level Data Acquisition for the Optical Synchronization System at European XFEL controls, laser, data-acquisition, database 2167
 
  • M. Schütte, A. Eichler, T. Lamb, V. Rybnikov, H. Schlarb, T. Wilksen
    DESY, Hamburg, Germany
  
  The optical synchronization system for the European X-Ray Free-Electron Laser provides sub-10 femtosecond timing precision * for the accelerator subsystems and experiments. This is achieved by phase locking a mode-locked laser oscillator to the main RF reference and distributing the optical pulse train carrying the time information via actively propagation-time stabilized optical fibers to multiple end-stations. Making up roughly one percent of the entire European XFEL, it is the first subsystem to receive a large-scale data acquisition system [2] for storing not just hand-selected information, but in fact all diagnostic, monitoring, and configuration data relevant to the optical synchronization available from the distributed control system infrastructure. A minimum of 100 TB per year may be stored in a persistent archive for long-term health monitoring and data mining whereas excess data is stored in a short-term ring buffer for high-resolution fault analysis and feature extraction algorithm development. This paper describes scale, challenges and first experiences from the optical synchronization data acquisition system.
* S. Schulz et al., "Few-Femtosecond Facility-Wide Sync. of the European XFEL," in Proc. FEL’19
** T. Wilksen et al., "A Bunch-Sync. DAQ System for the European XFEL," in Proc. ICALEPCS’17 		 
poster icon Poster TUPAB291 [0.281 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB291  
About • paper received ※ 14 May 2021       paper accepted ※ 17 June 2021       issue date ※ 24 August 2021  
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TUPAB313 Arrangement Optimization of Quadrupoles and Correctors for Beam Alignment quadrupole, alignment, focusing, electron 2221
 
  • L. Xu, Q.M. Zhang
    Xi’an Jiaotong University, People’s Republic of China
  • H.X. Deng
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • N. Huang
    UCAS, Beijing, People’s Republic of China
  • N. Huang
    SINAP, Shanghai, People’s Republic of China
  
  In the X-ray free-electron laser (XFEL), the alignment and stability of beam orbit have a great impact on power and qualities of the generated X-ray pulses. Currently, the beam-based alignment (BBA) is the most widely used technique in beam alignment. In order to find the best arrangement of quadrupoles and correctors, a mathematical model is established based on the transmission matrix method. With this model, several simple arrangements of quadrupoles and correctors are selected to simulate the beam alignment process. It is found that when two correctors adjust two quadrupoles, the beam can pass through the center of quadrupoles approximately collimated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB313  
About • paper received ※ 16 May 2021       paper accepted ※ 31 August 2021       issue date ※ 16 August 2021  
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TUPAB386 Design Study of the Nb3Sn Cos-Theta Dipole Model for FCC-hh dipole, superconductivity, collider, FEM 2421
 
  • R.U. Valente
    La Sapienza University of Rome, Rome, Italy
  • S. Burioli, P. Fabbricatore, S. Farinon, F. Levi, R. Musenich, A. Pampaloni
    INFN Genova, Genova, Italy
  • E. De Matteis, M. Statera
    INFN/LASA, Segrate (MI), Italy
  • F. Lackner, D. Tommasini
    CERN, Meyrin, Switzerland
  • S. Mariotto, M. Prioli
    INFN-Milano, Milano, Italy
  • M. Sorbi
    Universita’ degli Studi di Milano & INFN, Segrate, Italy
  
  In the context of the Future Circular Collider hadron-hadron (FCC-hh) R&D program, the Italian Institute of Nuclear Physics (INFN), in collaboration with CERN, is responsible for designing and constructing the Falcon Dipole (Future Accelerator post-LHC Costheta Optimized Nb3Sn Dipole), which is an important step towards the construction of High Field Nb3Sn magnets for a post LHC collider. The magnet is a short model with one aperture of 50 mm and the target bore field is 12 T (14 T ’ultimate’ field). The dipole is pre-loaded with the Bladder&Key technique to minimize the stress on the coils at room temperature, which are prone to degradation because of the Nb3Sn cable strain-sensitivity. The electro-mechanical 2D design is focused on the performance, the field quality and the quench protection, with emphasis to the stresses on the the conductor. The Falcon Dipole has been modelled in a 3D FEM to determine the peak field distribution and the influence of the coil ends on the field quality.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB386  
About • paper received ※ 19 May 2021       paper accepted ※ 21 June 2021       issue date ※ 19 August 2021  
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WEPAB045 European XFEL High-Power RF System - the First 4 Years of Operation klystron, operation, GUI, electron 2708
 
  • M. Bousonville, S. Choroba, T. Grevsmühl, S. Göller, A. Hauberg, V.V. Katalev, K. Machau, V. Vogel, B. Yildirim
    DESY, Hamburg, Germany
  
  In 2016, the installation of the European XFEL was completed and its 26 RF stations started operation in 2017. Each RF station consists of a 10 MW-1.3 GHz-multibeam klystron, a HV pulse modulator and a waveguide system to supply the superconducting cavities and the normal-conducting electron gun with RF power. During commissioning and subsequent operation, the RF stations were closely monitored and causes of failures were investigated. For the optimisation of the RF systems, the various RF station failures were evaluated according to their impact on accelerator operation and the measures to eliminate them were prioritised accordingly. This report describes the operation experience and improvements of the high-power RF stations during the first 4 years of operation.  
poster icon Poster WEPAB045 [6.887 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB045  
About • paper received ※ 19 May 2021       paper accepted ※ 07 June 2021       issue date ※ 21 August 2021  
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WEPAB056 Advanced Photoinjector Development at the UCLA SAMURAI Laboratory emittance, gun, linac, simulation 2728
 
  • A. Fukasawa, G. Andonian, O. Camacho, C.E. Hansel, G.E. Lawler, W.J. Lynn, N. Majernik, P. Manwani, B. Naranjo, J.B. Rosenzweig, Y. Sakai, O. Williams
    UCLA, Los Angeles, California, USA
  • Z. Li, R. Robles, S.G. Tantawi
    SLAC, Menlo Park, California, USA
  • J.I. Mann
    PBPL, Los Angeles, USA
  • M. Yadav
    The University of Liverpool, Liverpool, United Kingdom
  
  Funding: This work was supported by the US Department of Energy under the contract No. DE-SC0017648, DE-SC0009914, and DE-SC0020409, and by National Science Foundation Grant No. PHY-1549132
UCLA has recently constructed SAMURAI, a new radiation bunker and laser infrastructure for advanced accelerator research. In its first phase, we will build a 30 MeV photoinjector with an S-band hybrid gun. The beam dynamics simulation for this beamline showed the generation of the beam with the emittance 2.4 um and the peak current 270 A. FIR-FEL experiments are planned in this beamline. The saturation peak power was expected at 170 MW. 		 
poster icon Poster WEPAB056 [0.939 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB056  
About • paper received ※ 28 May 2021       paper accepted ※ 01 July 2021       issue date ※ 11 August 2021  
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WEPAB071 Design and Construction of an Intense Terahertz-Wave Source Based on Coherent Cherenkov Radiation Matched to Circle Plane Wave radiation, electron, experiment, controls 2751
 
  • N. Sei, H. Ogawa
    AIST, Tsukuba, Ibaraki, Japan
  • K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Sumitomo, Y. Takahashi, T. Tanaka
    LEBRA, Funabashi, Japan
  • T. Takahashi
    Kyoto University, Research Reactor Institute, Osaka, Japan
  
  Funding: This work was supported by Japan Society for the Promotion of Science KAKENHI JP19H04406 and the Visiting Researchers Program of Kyoto University Research Reactor Institute (R2013).
National Institute of Advanced Industrial Science and Technology has been studied terahertz (THz) coherent radiation in collaboration with Nihon University and Kyoto University. We have been developed a coherent transition radiation (CTR) source with macropulse power of 1 mJ using a screen monitor in the parametric X-ray line at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. However, to obtain a THz-wave source with higher intensity, we have undertaken a development of a new THz-wave source based on coherent Cherenkov radiation (CCR) matched to circle plane wave. Bypassing an electron beam through a hollow conical dielectric having an apex angle equal to the Cherenkov angle, the wavefront of the CCR generated on the inner surface of the hollow conical dielectric matches on the basal plane. Therefore, it is possible to obtain a high-power beam that is easy to transport. We have already produced a hollow conical dielectric made of high-resistivity silicon and considered a position controller for the hollow conical dielectric. In this presentation, the status of the new THz-wave source will be reported. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB071  
About • paper received ※ 18 May 2021       paper accepted ※ 22 June 2021       issue date ※ 21 August 2021  
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WEPAB072 PAX: A Plasma-Driven Attosecond X-Ray Source plasma, electron, experiment, simulation 2755
 
  • C. Emma, J. Cryan, M.J. Hogan, K. Larsen, J.P. MacArthur, A. Marinelli, G.R. White, X.L. Xu
    SLAC, Menlo Park, California, USA
  • A.C. Fisher, R.M. Hessami, P. Musumeci
    UCLA, Los Angeles, California, USA
  • R. Robles
    Stanford University, Stanford, California, USA
  
  Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515. This work was also partially supported by DOE grant DESC0009914
Plasma accelerators can generate ultra high brightness electron beams which open the door to light sources with smaller physical footprint and properties unachievable with conventional accelerator technology. In this work * we show that electron beams from Plasma WakeField Accelerators (PWFAs) can generate coherent tunable soft X-ray pulses with TW peak power and duration of tens of attoseconds in a meter-length undulator. These X-ray pulses are an order of magnitude more powerful, shorter and can be produced with better stability than state-of-the-art X-ray Free Electron Lasers (XFELs). The X-ray emission in this approach is driven by coherent radiation from a pre-bunched, near Mega Ampere (MA) current electron beam of attosecond duration rather than the SASE FEL process starting from noise. This approach significantly relaxes the restrictive requirements on emittance, energy spread, and pointing stability which has thus far hindered the realization of a high-gain FEL driven by a plasma accelerator. We discuss the approach and progress towards the experimental realization of this concept at the FACET-II accelerator facility.
* C. Emma, X. Xu, A. Fisher, J. P. MacArthur, J. Cryan, M. J. Hogan, P. Musumeci, G. White, A. Marinelli, "Terawatt attosecond X-ray source driven by a plasma accelerator", arXiv:2011.07163 (2020) 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB072  
About • paper received ※ 20 May 2021       paper accepted ※ 24 June 2021       issue date ※ 31 August 2021  
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WEPAB115 Beam Preparation with Temporally Modulated Photocathode Laser Pulses for a Seeded THz FEL laser, cathode, electron, simulation 2866
 
  • G.Z. Georgiev, N. Aftab, P. Boonpornprasert, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, A. Lueangaramwong, D. Melkumyan, S.K. Mohanty, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
    DESY Zeuthen, Zeuthen, Germany
  • N. Chaisueb
    Chiang Mai University, Chiang Mai, Thailand
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  
  The need for carrier-envelope-phase (CEP) stable THz pump pulses is recognized at many pump-probe experiments at the European XFEL. At the Photo Injector Test Facility at DESY in Zeuthen (PITZ), a proof-of-principle experiment of an accelerator-based THz FEL source is in preparation. Since the CEP stability of FEL pulses is not guaranteed in the SASE regime, a seeding scheme is needed. A common scheme for seeding is to drive the microbunching process with external laser pulses, which are power-limited in the THz range. Alternatively, a pre-bunched beam, generated for example by applying a temporally modulated photocathode laser pulse, can be used to drive the FEL. The beam dynamics with such a seeding method are studied with ASTRA tracking code simulations with space-charge forces as well as experimentally. The results of these studies are shown and discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB115  
About • paper received ※ 19 May 2021       paper accepted ※ 27 July 2021       issue date ※ 26 August 2021  
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WEPAB126 Pulsed Wire Magnetic Field Measurement System for Short-Period Long Undulators undulator, laser, detector, electron 2903
 
  • J.E. Baader, S. Casalbuoni
    EuXFEL, Schenefeld, Germany
  
  The pulsed wire method is an attractive option to measure the magnetic field in insertion devices, mainly for those with restricted access (e.g., small gaps, in-vacuum/cryogenic environments, etc.). Besides first and second field integrals, experiments have proved the feasibility of reconstructing the magnetic field profile. Undulators with a small gap and short period are - and are planned to be - used at diffraction-limited storage rings and free-electron lasers. This contribution outlines the pulsed wire system’s requirements to perform magnetic field reconstruction in such undulators. We examine the main expected limitations, particularly the dispersive, finite pulse-width, discretization error, and sag effects. Furthermore, we present the current status of developing the pulsed wire system at the European XFEL.  
poster icon Poster WEPAB126 [1.184 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB126  
About • paper received ※ 19 May 2021       paper accepted ※ 07 July 2021       issue date ※ 19 August 2021  
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WEPAB132 Towards a Superconducting Undulator Afterburner for the European XFEL photon, undulator, electron, vacuum 2921
 
  • S. Casalbuoni, J.E. Baader, G. Geloni, V. Grattoni, D. La Civita, C. Lechner, B. Marchetti, S. Serkez, H. Sinn
    EuXFEL, Schenefeld, Germany
  • W. Decking, L. Lilje, S. Liu, T. Wohlenberg, I. Zagorodnov
    DESY, Hamburg, Germany
  
  We propose to develop, characterize and operate a superconducting undulator (SCU) afterburner consisting of 5 undulator modules (1 module = 2 times SCU coil of 2 m length and 1 phase shifter) at the SASE2 hard X-ray beamline of European XFEL. This afterburner has the potential to produce an output of more than 1010 ph/pulse at photon energies above 30 keV. The project is divided into the production of a pre-series prototype module and a small-series production of 5 modules. Central goals of this R&D activity are: the demonstration of the functionality of SCUs at an X-ray FEL, the set up of the needed infrastructure to characterize and operate SCUs, the industrialization of such undulators, and the reduction of the price per module. In this contribution, the main parameters and specifications of the pre-series prototype module (S-PRESSO) are described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB132  
About • paper received ※ 15 May 2021       paper accepted ※ 05 July 2021       issue date ※ 14 August 2021  
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WEPAB135 Progress of the Development of a Superconducting Undulator as a THz Source for FELs undulator, radiation, electron, experiment 2933
 
  • J. Gethmann, S. Casalbuoni, N. Glamann, A.W. Grau, A.-S. Müller, D. Saez de Jauregui
    KIT, Karlsruhe, Germany
  • D. Astapovych, H. De Gersem, E. Gjonaj
    TEMF, TU Darmstadt, Darmstadt, Germany
  • S. Casalbuoni
    EuXFEL, Schenefeld, Germany
  
  Funding: This work is supported by the BMBF project 05K19VK2 SCUXFEL (Federal Ministry of Education and Research) and by the DFG-funded Doctoral School KSETA: Science and Technology.
To produce radiation in the THz frequency range at X-ray Free Electron Lasers, undulators with large period length, high fields, and large gaps are required. These demands can be fulfilled by superconducting undulators. In this contribution, the actual requirements on the main parameters of such a superconducting undulator will be discussed and the progress of the design will be discussed. In addition, beam impedance and heat load results obtained analytically as well as by large-scale wakefield simulations will be presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB135  
About • paper received ※ 19 May 2021       paper accepted ※ 02 July 2021       issue date ※ 31 August 2021  
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WEPAB172 Recent Developments of the IDEAS-Halo Detector experiment, detector, electron, vacuum 3005
 
  • A. Liu, J.R. Callahan, B.T. Freemire
    Euclid TechLabs, Solon, Ohio, USA
  • J.F. Power, J.H. Shao
    ANL, Lemont, Illinois, USA
  
  Funding: This work was performed at Euclid and Argonne National Laboratory, and was supported by the US DOE Office of Science under contract number DE-SC0019538.
Euclid Techlabs has been designing and testing a cost-effective iris diaphragm beam halo/profile detector, which can be easily configured to work with various primary beam energies and sites. Besides working as a measurement device, it can also work as a controllable beam scraper/collimator. This novel iris diaphragm detector utilizes the current signal produced by the beam charge deposition on the moveable conductive iris blades, to accurately measure the beam distribution from the outlier to the beam core. In this paper, we discuss the recent developments of our iris diaphragm e-beam apparatus series (IDEAS)-halo detector, including its geometry upgrades and newest beam experiments done at the AWA cathode testbed (ACT) of Argonne National Laboratory. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB172  
About • paper received ※ 03 June 2021       paper accepted ※ 22 July 2021       issue date ※ 27 August 2021  
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WEPAB181 New Opportunities in Low Energy Antiproton Research electron, proton, antiproton, experiment 3035
 
  • C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  
  Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 721559.
Experiments with low-energy antiprotons are at the cutting edge of science and offer unique opportunities to test some of the fundamental laws of physics. The experiments are, however, very difficult to realize. They critically depend on high-performance numerical tools that can model realistic beam transport and storage and also require advanced beam monitors and detectors that can fully characterize the beam. Finally, novel experiments need to be designed that exploit the enhanced beam quality that the new ELENA ring at CERN provides. This paper presents some selected findings from the pan-European AVA network’s three scientific work packages. It shows results from studies into electron cooling at the new ELENA storage ring, research into carbon nanotubes as cold electron field emitters for electron cooling, and how antiproton-atom collision experiments can be optimized using GEANT4. Finally, the paper gives an overview of the network’s interdisciplinary training program. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB181  
About • paper received ※ 16 May 2021       paper accepted ※ 11 June 2021       issue date ※ 11 August 2021  
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WEPAB184 Optimization of Medical Accelerators proton, network, medical-accelerators, detector 3042
 
  • C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sk’odowska-Curie grant agreement No 675265.
Between 2016 and 2020, 15 Fellows have carried out collaborative research within the 4 MEUR Optimization of Medical Accelerators (OMA) EU-funded innovative training network. Based at universities, research and clinical facilities, as well as industry partners in several European countries, the Fellows have successfully developed a range of beam and patient imaging techniques, improved biological and physical models in Monte Carlo codes, and also help improve the design of existing and future clinical facilities. This paper gives an overview of the research outcomes of this network. It presents results from tracking and LET measurements with the MiniPIX-TimePIX detector for 60 MeV clinical protons, a new treatment planning approach accounting for prompt gamma range verification and interfractional anatomical changes, and summarizes findings from high-gradient testing of an S-band, normal-conducting low phase velocity accelerating structure. Finally, it gives a brief over-view of the scientific and training events organized by the OMA consortium. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB184  
About • paper received ※ 16 May 2021       paper accepted ※ 14 July 2021       issue date ※ 21 August 2021  
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WEPAB229 Transverse Density Pileup and Pattern Formation in Dense Ultracold Electron Beamlets under Coulomb Expansion electron, simulation, ECR, damping 3169
 
  • A.J. Tencate, K. Bhuyan, B. Erdélyi
    Northern Illinois University, DeKalb, Illinois, USA
  
  Funding: This work was sponsored by the US Department of Energy Office of Science under Grant DE-SC0020241.
Dynamic Coulomb expansion of dense particle bunches can lead to transverse density shock-like propagation for nonuniform bunch distributions. Furthermore, under favorable circumstances, multiple bunches in close proximity can collide without crossing to form wheel-and-spoke patterns. This process has been observed experimentally for Rubidium ions, but not yet for electrons, where the dynamics occur over far shorter length scales. We simulate the interaction of electron bunches while varying the initial transverse temperature and density profiles to determine the thresholds that characterize this pattern formation. Additionally, we consider the effects of asymmetries and the impact of a low-density halo on the overall process. The simulations are conducted using a novel high-fidelity algorithm for collisional particle dynamics. 		 
poster icon Poster WEPAB229 [7.411 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB229  
About • paper received ※ 19 May 2021       paper accepted ※ 02 July 2021       issue date ※ 13 August 2021  
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WEPAB251 Beam Dynamics Optimization of LCLS-II HE Linear Accelerator Design emittance, electron, undulator, radiation 3224
 
  • J. Qiang
    LBNL, Berkeley, California, USA
  • T.O. Raubenheimer, M.D. Woodley
    SLAC, Menlo Park, California, USA
  
  The LCLS-II-HE as a high energy upgrade of the high repetition rate X-ray FEL under construction at SLAC will provide great opportunities for scientific discovery by generating coherent, high brightness hard X-ray radiation. In this paper, we report on beam dynamics optimization of the LCLS-II HE linear accelerator design with a 100pC and a 20pC charge beam to attain high quality electron beam for X-ray FEL radiation. We also present preliminary results of beam dynamics optimization of a 100pC beam from a low emittance superconducting injector.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB251  
About • paper received ※ 18 May 2021       paper accepted ※ 21 June 2021       issue date ※ 30 August 2021  
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WEPAB257 Matching of a Space-Charge Dominated Beam into the Undulator of the THz SASE FEL at PITZ undulator, electron, experiment, quadrupole 3244
 
  • X. Li, Z. Aboulbanine, G.D. Adhikari, N. Aftab, Z.G. Amirkhanyan, P. Boonpornprasert, M.E. Castro Carballo, N. Chaisueb, G.Z. Georgiev, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, O. Lishilin, A. Lueangaramwong, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
    DESY Zeuthen, Zeuthen, Germany
  
  The Photo Injector Test facility at DESY in Zeuthen (PITZ) is developing a THz SASE FEL as a prototype high repetition rate accelerator-based source for the THz-pumped, X-ray-probed experiments at the European XFEL. For the generation of THz pulses of mJ-level energy from SASE, an electron beam with a high charge (up to 4 nC) and high peak current (~200 A) will be injected into an LCLS-I undulator, which is currently being installed at the end of the photo-injector. The narrow vacuum chamber (11x5 mm) between the magnetic poles and the strong vertical focusing from the undulator, as well as the lack of beam diagnostics, have made it a challenge to match the space-charge dominated beam into the undulator without beam loss during the following transport. In this paper, boundary conditions of a matched electron beam will be discussed and the simulation and experimental study on our matching strategy will be presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB257  
About • paper received ※ 08 May 2021       paper accepted ※ 02 July 2021       issue date ※ 13 August 2021  
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WEPAB274 Numerical Study of Beam Dynamics in PITZ Bunch Compressor simulation, laser, booster, gun 3285
 
  • A. Lueangaramwong, Z. Aboulbanine, G.D. Adhikari, N. Aftab, P. Boonpornprasert, N. Chaisueb, G.Z. Georgiev, J. Good, M. Groß, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, D. Melkumyan, H.J. Qian, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
    DESY Zeuthen, Zeuthen, Germany
  • H. Shaker
    CLS, Saskatoon, Saskatchewan, Canada
  
  A magnetic bunch compressor has been recently designed for an accelerator-based THz source which is under development at the Photo Injector Test facility at DESY in Zeuthen (PITZ). The THz source is assumed to be a prototype for an accelerator-based THz source for pump-probe experiments at the European XFEL. As an electron bunch is compressed to achieve higher bunch currents for the THz source, we investigate the beam dynamics in the bunch compressor by numerical simulations. A start-to-end simulation optimizer has been developed by combining the use of ASTRA, IMPACT-T, and OCELOT to support the design of the THz source prototype. Coherent synchrotron radiation effects degrade the compression performance for our study cases with bunch charges up to 4 nC and beam energy of 17 MeV at a bending angle of 19 degrees. Simulation and preliminary beam characteristic results will be presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB274  
About • paper received ※ 11 May 2021       paper accepted ※ 06 July 2021       issue date ※ 23 August 2021  
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WEPAB285 High Resolution Arrival Time Measurement of the Seed Laser laser, timing, electron, experiment 3320
 
  • J.G. Wang, H.X. Deng, L. Feng, C.L. Li, B. Liu
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • X.T. Wang, W.Y. Zhang
    Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
  
  The Shanghai soft X-ray Free-Electron Laser facility (SXFEL) is a fourth-generation linac-based light source, capable of producing X-ray pulses with a duration of tens of femtosecond. The seed laser for external seeding FEL, therefore, has tight requirements for relative arrival time to the electron bunch. To reach the required energy and wavelength for external seeding FEL, further optical amplification and frequency conversion is needed. These include reflection and propagation in different material and in air, in addition, also include the long laser transport beamline to the undulator, make the laser pulses arrival time influenced by environmental variation. To reach the required specification, high-resolution measurement of the laser arrival time is necessary. In this paper, we present a general concept for the measurement of the laser arrival time.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB285  
About • paper received ※ 19 May 2021       paper accepted ※ 12 July 2021       issue date ※ 12 August 2021  
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WEPAB288 A New Timing System for PETRA IV timing, controls, storage-ring, hardware 3329
 
  • H. Lippek, A. Aghababyan, K. Brede, H.T. Duhme, M. Fenner, U. Hurdelbrink, H. Kay, H. Schlarb, T. Wilksen
    DESY, Hamburg, Germany
  
  At DESY an upgrade of the PETRA III synchrotron light source towards a fourth-generation, low emittance machine PETRA IV is currently being actively pursued. The realization of this new machine implies a new design of the timing and synchronization system since requirements on beam quality and controls will significantly change from the existing implementation at PETRA III. As of now the technical design phase of the PETRA IV project is in full swing. For the timing system the design process of the overall system as well as the evaluation of individual components has been started as of last year. Given the success of the at DESY developed MicroTCA.4-based timing system for the European XFEL accelerator it has been chosen to serve as a basis for the PETRA IV timing system developement as well. We present first design ideas of the major timing system hardware component, a MicroTCA.4-based AMC for distributing clocks, triggers and further bunch-synchronous information within the accelerator complex and to user experiments. First steps of an evaluation process for designing the AMC hardware are briefly illustrated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB288  
About • paper received ※ 19 May 2021       paper accepted ※ 01 July 2021       issue date ※ 10 August 2021  
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WEPAB293 The Trip Event Logger for Online Fault Diagnosis at the European XFEL controls, cavity, operation, EPICS 3344
 
  • J.H.K. Timm, J. Branlard, A. Eichler, H. Schlarb
    DESY, Hamburg, Germany
  
  The low-level RF (LLRF) system at the European XFEL, DESY, is of major importance for a high-performant and reliable operation. Faults here can jeopardize the overall operation. Therefore, the trip event logger is currently developped, - a fault diagnosis tool to detect errors online, inform the operators and trigger automatic supervisory actions. Further goals are to provide information for a fault tree and event tree analysis as well as a database of labeled faulty data sets for offline analysis. The tool is based on the C++ framework ChimeraTK Application Core. With this close interconnection to the control system it is possible not only to monitor but also to intervene as it is of great importance for supervisory tasks. The core of the tool consists of fault analysis modules ranging from simple ones (e.g., limit checking) to advanced ones (model-based, machine learning, etc.). Within this paper the architecture and the implementation of the trip event logger are presented.  
poster icon Poster WEPAB293 [7.919 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB293  
About • paper received ※ 19 May 2021       paper accepted ※ 02 July 2021       issue date ※ 10 August 2021  
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WEPAB318 Prediction and Clustering of Longitudinal Phase Space Images and Machine Parameters Using Neural Networks and K-Means Algorithm network, simulation, electron, ECR 3417
 
  • M. Maheshwari
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • D.J. Dunning, J.K. Jones, M.P. King, H.R. Kockelbergh, A.E. Pollard
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  Machine learning algorithms were used for image and parameter recognition and generation with the aim to optimise the CLARA facility at Daresbury, using start-to-end simulation data. Convolutional and fully connected neural networks were trained using TensorFlow-Keras for different instances, with examples including predicting Longitudinal Phase Space (LPS) images with machine parameters as input and FEL parameter prediction (e.g. pulse energy) from LPS images. The K-means clustering algorithm was used to cluster the LPS images to highlight patterns within the data. Machine learning techniques can enhance the way large amounts of data are processed and analysed and so have great potential for application in accelerator science R&D.  
poster icon Poster WEPAB318 [1.062 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB318  
About • paper received ※ 17 May 2021       paper accepted ※ 05 July 2021       issue date ※ 21 August 2021  
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WEPAB322 Status of Digital BPM Signal Processor for SHINE cavity, FPGA, electron, electronics 3430
 
  • L.W. Lai, F.Z. Chen, Y.B. Leng, T. Wu, Y.M. Zhou
    SSRF, Shanghai, People’s Republic of China
  • J. Wan
    SINAP, Shanghai, People’s Republic of China
  
  Funding: Youth Innovation Promotion Association, CAS (Grant No. 2019290); The National Key Research and Development Program of China (Grant No. 2016YFA0401903).
Digital signal processors that can handle 1MHz bunch rate BPM signal processing are under development for SHINE. Two different processors have been developed at the same time, including an intermediate frequency signal processor with a sampling rate higher than 500MHz, which can be used in general BPM applications; and a direct RF sampling processor, which can directly sample the C band cavity BPM signal without analog down-conversion modules and greatly simplifies the cavity BPM system. This paper will introduce the design, development status, and performance evaluations of the processors. 		 
poster icon Poster WEPAB322 [1.919 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB322  
About • paper received ※ 20 May 2021       paper accepted ※ 10 June 2021       issue date ※ 24 August 2021  
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WEPAB379 Photocathode Laser Development for Superconducting X-Ray Free Electron Lasers at DESY laser, operation, cathode, electron 3599
 
  • C. Li, O. Akcaalan, U. Grosse-Wortmann, I. Hartl, C. Mohr, M. Seidel, H. Tuennermann, C. Vidoli, L. Winkelmann
    DESY, Hamburg, Germany
  • M. Frede, O. Puncken
    neoLASE GmbH, Hanover, Germany
  
  Funding: Deutsches Elektronen-Synchrotron, Hamburg, 22609, Germany
Modern X-Ray Free-Electron Lasers (XFEL) are a key tool to enable a variety of scientific research. Those large-scale machines rely on robust and reliable deep ultraviolet (DUV) laser sources to drive electrons from their RF photocathode gun. In this paper we present a new photocathode laser prototype, which offers more flexibility in duration and shape of the 257.5 nm pulses for driving the CsTe Photocathodes of DESY’s superconducting burst-mode FELs. The laser matches the FEL pulse structure, which are 800 µs bursts at up to 4.5 MHz intraburst-rate with 10 Hz burst-repetition-rate. In a first version the system will offer variable DUV pulse durations, tunable from 1 ps to 20 ps to address different operational regimes of the XFEL. The laser system comprises a high-resolution spectral shaper with the option of generating flat-top DUV pulses for reducing electron-beam emittance at a later version. The laser is constructed in a hybrid Yb:fiber and Yb:YAG architecture. Our prototype delivers 180 uJ pulse energy at 1030 nm and 1 MHz intra-burst rate and we demonstrated conversion of 50µJ of the NIR beam to DUV, resulting 11.5µJ at 21ps (FWHM) and 6.15 µJ at 1.05 ps (FWHM) pulse duration. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB379  
About • paper received ※ 27 May 2021       paper accepted ※ 02 July 2021       issue date ※ 23 August 2021  
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THXA04 Microbunching Instability in the Presence of Intrabeam Scattering for Single-Pass Accelerators electron, bunching, scattering, simulation 3692
 
  • C.-Y. Tsai
    HUST, Wuhan, People’s Republic of China
  • W. Qin
    Lund University, Lund, Sweden
  
  Funding: This work is supported by the Fundamental Research Funds for the Central Universities under Project No. 5003131049 and National Natural Science Foundation of China under project No. 11905073.
Intrabeam scattering (IBS) has long been studied in lepton or hadron storage rings as a slow diffusion process, while the effects of IBS on single-pass or recirculating electron accelerators have drawn attention only in the recent two decades due to the emergence of linac-based or ERL-based 4th-generation light sources, which require high-quality electron beams during the beam transport. Recent experimental measurements indicate that in some parameter regimes, IBS can have a significant influence on microbunched beam dynamics. Here we develop a theoretical formulation* of microbunching instability (MBI) in the presence of IBS for single-pass accelerators. We start from the Vlasov-Fokker-Planck (VFP) equation, combining both collective longitudinal space charge and incoherent IBS effects. The linearized VFP equation with the corresponding coefficients is derived. The evolutions of the phase space density and energy modulations are formulated as a set of coupled integral equations. The formulation** is then applied to a simplified single-pass transport line. The results from the semi-analytical calculation are compared and show good agreement with particle tracking simulations.
* C.-Y. Tsai et al., Phys. Rev. Accel. Beams 23, 124401 (2020)
** C.-Y. Tsai and W. Q, Phys. Plasmas (2021), accepted for publication 		 
slides icon Slides THXA04 [2.699 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA04  
About • paper received ※ 13 May 2021       paper accepted ※ 19 July 2021       issue date ※ 13 August 2021  
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THXB02 Beam Arrival Stability at the European XFEL laser, timing, electron, feedback 3714
 
  • M.K. Czwalinna, J. Kral, B. Lautenschlager, J. Müller, H. Schlarb, S. Schulz, B. Steffen
    DESY, Hamburg, Germany
  • R. Boll, H. Kirkwood, J. Koliyadu, R. Letrun, J. Liu, F. Pallas, D.E. Rivas, T. Sato
    EuXFEL, Schenefeld, Germany
  
  Free electron laser facilities, such as the European XFEL, make increasingly high demands on the longterm temporal stability and uniformity of the electron bunches, as pump-probe experiments meanwhile aim for timing stabilities of few femtoseconds residual jitter only. For a beam-based feedback control of the linear accelerator, electro-optical bunch arrival-time monitors are deployed, achieving a time resolution better than 3 fs. In a first attempt, we recently demonstrated a beam-based feedback system, reducing the arrival time jitter of the electron bunches to the 10 fs level with stable operation over hours. For pump-probe experiments it is crucial to equally verify this new level of precision in the FEL pulse arrival time with independent methods. In this work, we are discussing first results from examining the facility-wide temporal stability at the European XFEL, with attention to the contributions of various sub-systems and on the different time scales.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB02  
About • paper received ※ 19 May 2021       paper accepted ※ 20 July 2021       issue date ※ 23 August 2021  
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THXB07 Coherent Radiation From Inverse Compton Scattering Sources by Means of Particle Trapping electron, laser, radiation, undulator 3732
 
  • A. Fallahi, L. Novotny
    ETH Zurich, Photonics Laboratory, Zurich, Switzerland
  • N. Kuster
    ETH, Zurich, Switzerland
  
  Funding: This work is supported by the Swiss National Science Foundation (SNSF) under the Spark grant CRSK-2-190840.
Inverse Compton scattering (ICS) sources are one of the promising compact tools to generate short wavelength radiation from electron beams based on the relativistic Doppler effect. Nonetheless, these sources suffer from a few shortcomings such as incoherent radiation and low-efficiency in radiation generation. This contribution presents a novel scheme based on the scattering of an optical beam from a trapped electron beam inside an optical cavity. Inverse-Compton scattering off both free and trapped electrons are simulated using a full-wave solution of first-principle equations based on FDTD/PIC in the co-moving frame of electron beams. It is shown that the strong space-charge effect in low-energies is the main obstacle in acquiring coherent gain through the ICS mechanism. Subsequently, it is shown that by trapping the electron beam to the high-intensity spots, the space-charge effect is compensated, and additionally, the ultrahigh charge density enables high FEL-gain at trapping spots, thereby augmenting the coherence of the output radiation and concurrently increasing the source efficiency by three orders of magnitude. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXB07  
About • paper received ※ 28 May 2021       paper accepted ※ 01 July 2021       issue date ※ 24 August 2021  
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THPAB035 Study of the Tolerances for Superconducting Undulators at the European XFEL undulator, electron, simulation, photon 3819
 
  • B. Marchetti, S. Casalbuoni, V. Grattoni, S. Serkez
    EuXFEL, Schenefeld, Germany
  
  European XFEL is investing in the development of superconducting undulators (SCUs) for future upgrade of its beamlines SCUs made of NbTi, working at 2K, with a period length of 15 mm and a vacuum gap of 5 mm allow covering a range between 54 keV and 100 keV for 17.5 GeV electron energy. The effect of mechanical errors in the distribution of K along the undulators is more relevant for working points at lower photon energy, which are obtained using a higher magnetic field in the undulator. In this article we investigate the effect of error distribution in the K-parameter for a working point at 50keV photon energy obtained injecting an electron beam with 16.5 GeV energy from the XFEL linear accelerator in a undulator line composed by SCUs with 1.58 T peak magnetic field.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB035  
About • paper received ※ 12 May 2021       paper accepted ※ 05 July 2021       issue date ※ 18 August 2021  
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THPAB036 Superconducting Phase Shifter Design for the Afterburner at the European XFEL electron, undulator, photon, operation 3823
 
  • V. Grattoni, J.E. Baader, S. Casalbuoni
    EuXFEL, Schenefeld, Germany
  
  At the European XFEL, a superconducting afterburner is under design for the SASE2 hard X-ray beamline. It will consist of 5 undulator modules. One module corresponds to two superconducting undulator (SCU) coils of 2 m length plus one phase shifter. Such an afterburner will enable photon energies above 30 keV. Superconducting (SC) phase shifters will be installed in each undulator module to keep the correct phase delay between the electron beam and photon beam. In this contribution, we present the required SC phase shifter parameters to enable operation in the electron beam energy range 11.5-17.5 GeV. We also analyze different magnetic designs satisfying the calculated specifications.  
poster icon Poster THPAB036 [0.991 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB036  
About • paper received ※ 18 May 2021       paper accepted ※ 06 July 2021       issue date ※ 12 August 2021  
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THPAB043 A Superconducting Undulator for CompactLight: Resistive Wall Wakefield Analysis undulator, wakefield, impedance, electron 3841
 
  • K.B. Marinov
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  
  The CompactLight project is an advanced X-ray FEL light source, with high-frequency, high-gradient linacs and compact undulators. Lower electron energies give higher energy efficiency and a smaller environmental footprint. The extremely short bunch lengths (few fs) and narrow undulator gaps (4 mm) drastically increase the impact of resistive wall wakefields on the lasing process. The longitudinal resistive wall wakefield impedance is calculated in the framework of the surface impedance approach, in accordance with anomalous skin effect (ASE) theory. The dependence of the electron energy loss factor and the correlated energy spread of the bunch on the residual resistivity ratio (RRR) for both copper and aluminum is much higher for long (100 fs) than for ultra-short (6 fs) bunches. This is due to a known property of the longitudinal wakefield impedance - the field acting on a single particle traversing a resistive vessel does not depend on the conductivity of the vessel. The wakefields generated by the ultra-short bunch are already close to that of a single-particle regime and this leads to interesting consequences which are discussed in the present work.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB043  
About • paper received ※ 19 May 2021       paper accepted ※ 21 June 2021       issue date ※ 21 August 2021  
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THPAB045 Design of a Short Period Helical Superconducting Undulator undulator, electron, photon, simulation 3844
 
  • A.G. Hinton
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • J. Boehm, L. Cooper, B. Green, T. Hayler, P. Jeffery, C.P. Macwaters
    STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
  • S. Milward
    DLS, Oxfordshire, United Kingdom
  • B.J.A. Shepherd
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • B.J.A. Shepherd
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  
  Superconducting technology provides the possibility to develop short period, small bore undulators that can generate much larger magnetic fields than alternative technologies. This may allow an XFEL with optimised superconducting undulators to cover a broader range of wavelengths than traditional undulators. At STFC, we have undertaken work to design and build a prototype helical superconducting undulator (HSCU) module with parameters suitable for use on a future XFEL facility. This work includes the design of a full 2 m long undulator module, including an undulator with 13 mm period and 5 mm inner winding diameter, the supporting cryogenic and vacuum systems required for operation, and quadrupoles, phase shifters and correction magnets for use between undulator sections. We present here the magnetic and mechanical design of the HSCU. The choice of undulator parameters and their influence on the design is discussed. A turnaround scheme to allow continuous winding of the undulator without the need for superconducting joints is also presented. Techniques for winding the undulator are currently being investigated and a short prototype will soon be wound and tested.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB045  
About • paper received ※ 17 May 2021       paper accepted ※ 18 June 2021       issue date ※ 21 August 2021  
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THPAB048 Design and Fabrication Concepts of a Compact Undulator with Laser-Structured 2G-HTS Tapes undulator, laser, simulation, impedance 3851
 
  • A. Will, T.A. Arndt, E. Bründermann, N. Glamann, A.W. Grau, B. Krasch, A.-S. Müller, R. Nast, D. Saez de Jauregui
    KIT, Karlsruhe, Germany
  • D. Astapovych, H. De Gersem, E. Gjonaj
    TEMF, TU Darmstadt, Darmstadt, Germany
  
  To produce small-scale high-field undulators for table-top free electron lasers (FELs), compact designs have been proposed using high temperature superconducting (HTS) tapes, which show both large critical current densities and high critical magnetic fields with a total tape thickness of about 50 μm and a width of up to 12 mm. Instead of winding coils, a meander structure can be laser-scribed directly into the superconductor layer, guiding the current path on a quasi-sinusoidal trajectory. Stacking pairs of such scribed tapes allows the generation of the desired sinusoidal magnetic fields above the tape plane, along the tape axis. Two practically feasible designs are presented, which are currently under construction at KIT: A coil concept wound from a single structured tape with a length of 15 m, which is a progression of a design that has been presented already in the past, as well as a novel stacked and soldered design, made from 25 cm long structured tapes, soldered in a zig-zag-pattern. In this contribution the designs are briefly recapped and the experimental progress is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB048  
About • paper received ※ 19 May 2021       paper accepted ※ 12 July 2021       issue date ※ 15 August 2021  
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THPAB049 Modeling the Magnetic Field of the LCLS-I Undulator for THz@PITZ undulator, simulation, vacuum, experiment 3855
 
  • M. Krasilnikov, X. Li, A. Lueangaramwong, F. Mueller, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • A. Brachmann, H.-D. Nuhn
    SLAC, Menlo Park, California, USA
  • M. Tischer, P. Vagin
    DESY, Hamburg, Germany
  
  Funding: This work was supported by the European XFEL research and development program
An accelerator-based THz source for pump-probe experiments at the European XFEL is under development at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). For the proof-of-principle experiments an LCLS-I undulator is planned to be installed downstream of the PITZ accelerator. The fields of the undulator module 26 have been re-measured at DESY in Hamburg and the results are consistent with earlier SLAC measurements. A model for 3D field reconstruction based on the undulator magnetic measurements has been developed. It includes also a horizontal gradient of the vertical field. Tracking of the 17 MeV/c beam has revealed that the transverse gradient will lead to a significant off-axis trajectory in the horizontal plane. This offset has to be corrected with a steering coil, the design of which is also presented. The performance of the THz generation with the correction coil is discussed as well. 		 
poster icon Poster THPAB049 [1.409 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB049  
About • paper received ※ 12 May 2021       paper accepted ※ 12 July 2021       issue date ※ 02 September 2021  
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THPAB053 Magnetic Field Calculation of Planar SCUs Using ANSYS Maxwell undulator, photon, software, software-tool 3868
 
  • Y. Shiroyanagi, E.A. Anliker, Q.B. Hasse, H. Hu, Y. Ivanyushenkov, M. Kasa, I. Kesgin
    ANL, Lemont, Illinois, USA
  
  Funding: This work was supported by U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) Upgrade includes a 4.8-m-long superconducting undulator (SCU) cryostat containing two 1.9-m-long, 16.5-mm-period planar NbTi undulator magnets. The magnetic and mechanical design of this magnet follows the design of the existing 1.1-m-long, 18-mm-period planar SCU that is currently in operation at the APS *. Although OPERA is a reliable standard software tool for magnetic field calculations, ANSYS Maxwell 3D has the advantage of calculating a large and complex geometry. In this paper, first, the magnetic field map, including the peak field and end fields, is bench-marked against the magnetic measurement data of the existing planar SCU18-1. Then, corrector current optimization is presented for the 1.5-m-long, 21-mm-period planar SCU. Finally, a magnetic field model of a full-scale, 1.9-m-long planar SCU is presented.
* Y. Ivanyushenkov et al., Phys. Rev. Accel. Beams 20, 100701 (2017).
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB053  
About • paper received ※ 18 May 2021       paper accepted ※ 18 June 2021       issue date ※ 11 August 2021  
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THPAB069 Design Concepts for a High-Gradient C-Band Linac cavity, electron, linac, accelerating-gradient 3919
 
  • T.B. Bolin, S.I. Sosa Guitron
    UNM-ECE, Albuquerque, USA
  • S. Biedron
    UNM-ME, Albuquerque, New Mexico, USA
  • J.R. Cary
    Tech-X, Boulder, Colorado, USA
  • M. Dal Forno
    SLAC, Menlo Park, California, USA
  
  Funding: This work was performed under Contract No. 89233218CNA000001, supported by the U.S. DOE’s National Nuclear Security Administration, for the operation of Los Alamos National Laboratory (LANL).
During the last decade, the production of soft to hard x-rays (up to 25 keV) at XFEL facilities has enabled new developments in a broad range of disciplines. One caveat is that these instruments can require a large amount of real estate. For example, the XFEL driver is typically an electron beam linear accelerator (LINAC) and the need for higher electron beam energies capable of generating higher energy X-rays can require longer linacs; costs quickly become prohibitive, requiring state of art methods. One cost-saving measure is to produce a high accelerating gradient while reducing cavity size. Compact accelerating structures are also high-frequency. Here, we describe design concepts for a high-gradient, cryo-cooled LINAC for XFEL facilities in the C-band regime (~4-8 GHz). We are also exploring C-band for different applications including drivers for security applications. We investigate 2 different traveling wave (TW) geometries optimized for high-gradient operation as modeled with VSim software. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB069  
About • paper received ※ 20 May 2021       paper accepted ※ 02 July 2021       issue date ※ 14 August 2021  
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THPAB080 Correcting the Magnetic Field Offsets Inside the Undulators of the EuXFEL Using the K-Monochromator undulator, radiation, electron, synchrotron 3953
 
  • F. Brinker
    DESY, Hamburg, Germany
  • S. Casalbuoni, W. Freund
    EuXFEL, Schenefeld, Germany
  
  Hard X-ray free-electron lasers (XFELs) generate intense coherent X-ray beams by passing electrons through undulators, i.e. very long periodic magnet structures, which extend over hundreds of meters. A crucial condition for the lasing process is the spatial overlap of the electrons with the electromagnetic field. Well-established electron beam-based procedures allow finding a straight trajectory for the electrons defined by the beam position monitors (BPM) between the undulators. A bending of the trajectory in between the BPMs cannot be seen by these methods. A general field offset inside the undulators has the effect that the synchrotron radiation is emitted at a different angle at the beginning and the end of the undulator which can result in a degradation of the FEL-gain especially for very short wavelengths. We report on how the spectral and spatial characteristics of the monochromatized radiation of a single undulator can be used to minimize the field offset in situ with the help of correction coils.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB080  
About • paper received ※ 19 May 2021       paper accepted ※ 25 June 2021       issue date ※ 12 August 2021  
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THPAB119 Many-Objective Beam Dynamics Optimization for High-Repetition-Rate XFEL Photoinjector emittance, electron, gun, laser 3991
 
  • Z.H. Zhu, J.W. Yan
    SINAP, Shanghai, People’s Republic of China
  • D. Gu
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • Q. Gu
    Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
  
  SHINE, as the first hard x-ray free-electron-laser (FEL) facility in China, is design to provide high-brightness FEL lasing under high-repetition-rate operation. In order to drive x-ray FEL pulses with high qualities, the photoinjector section is deployed to provide the specified electron beam with low transverse emittance and high brightness. Normally the multi-objective optimization algorithm is employed in the injector beam dynamics design. In this paper, the many-objective optimization algorithm NSGA-III is introduced to the injector physical design for optimizing the 4 detailed beam quality properties using 17 variables for the first time. The results of the optimization are presented and the correlations are analyzed. This approach can provide guidance for further physical research as well as improve the beam dynamics optimization efficiency.  
poster icon Poster THPAB119 [0.936 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB119  
About • paper received ※ 17 May 2021       paper accepted ※ 07 July 2021       issue date ※ 22 August 2021  
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THPAB120 Beam on Demand for High-Repetition-Rate X-Ray Free-Electron Lasers electron, laser, SRF, linac 3995
 
  • Z. Zhang, Y. Ding, Z. Huang
    SLAC, Menlo Park, California, USA
  
  High-repetition-rate (HRR) free-electron lasers (FELs) with multiple undulator beamlines will advance the frontiers of X-ray science significantly from the remarkable success of existing X-ray FEL facilities. The wide-ranging requirements for the photon properties from multiple beamlines are extremely challenging to satisfy by the same electron beam from a single superconducting radio-frequency (SRF) accelerator. To realize the full potential of an HRR FEL facility, a new emerging concept of "beam on demand" is proposed here. The concept is based on advanced beam dynamics and radio-frequency (RF) techniques to provide beam properties tailored to each undulator line at the desired repetition rate. The beam properties that will be pursued in this proposal include, but are not limited to, beam energy, bunch charge, bunch length, beam current, and its profile. The realization of "beam on demand" will allow optimization of photon properties of individual beamlines to maximize their performance and drastically improve the multiplexing capabilities of Linac Coherent Light Source II and its high-energy upgrade.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB120  
About • paper received ※ 17 May 2021       paper accepted ※ 23 July 2021       issue date ※ 27 August 2021  
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THPAB126 Operational Experience and Characterization of a Superconducting Transverse Gradient Undulator for Compact Laser Wakefield Accelerator-Driven FEL laser, electron, undulator, experiment 4009
 
  • K. Damminsek, A. Bernhard, J. Gethmann, A.W. Grau, A.-S. Müller, Y. Nie, M.S. Ning, S.C. Richter, R. Rossmanith
    KIT, Karlsruhe, Germany
  
  A 40-period superconducting transverse gradient undulator (TGU) has been designed and fabricated at Karlsruhe Institute of Technology (KIT). Combining a TGU with a Laser Wakefield Accelerator (LWFA) is a potential key for realizing an extremely compact Free Electron Laser (FEL) radiation source. The TGU scheme is a viable option to compensate the challenging properties of the LWFA electron beam in terms of beam divergence and energy spread. In this contribution, we report on the operational experience of this TGU inside its own cryostat and show the current status of the TGU and the further plan for experiments. This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB126  
About • paper received ※ 19 May 2021       paper accepted ※ 25 August 2021       issue date ※ 02 September 2021  
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THPAB151 The Advantage of Cold Electron Source in Electron Diffraction electron, simulation, experiment, ion-source 4053
 
  • J. Liu, H. Luo
    SWUST, Mianyang City, Sichuan Province, People’s Republic of China
  
  In this paper, a model for discussing the influence of transverse coherence of electron beams on electron diffraction is established. With reference to Fedele’s thermal-wave model, the transverse coherence length is introduced into this model to characterize the transverse coherence of electron beams. The simulation results show that the transverse coherence of electron beams has a significant influence on electron diffraction, and the cold electron source with high transverse coherence has an obvious advantage in electron diffraction.  
poster icon Poster THPAB151 [0.647 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB151  
About • paper received ※ 15 May 2021       paper accepted ※ 21 June 2021       issue date ※ 25 August 2021  
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THPAB217 Lightsource Unified Modeling Environment (LUME), a Start-to-End Simulation Ecosystem simulation, interface, software, electron 4212
 
  • C.E. Mayes, A.L. Edelen, P. Fuoss, J.R. Garrahan, A. Halavanau, F. Ji, J. Krzywiński, W. Lou, N.R. Neveu, H.H. Slepicka
    SLAC, Menlo Park, California, USA
  • J.C. E, C. Fortmann-Grote
    EuXFEL, Schenefeld, Germany
  • C.M. Gulliford, D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • L. Gupta
    University of Chicago, Chicago, Illinois, USA
  • A. Huebl, R. Lehé
    LBNL, Berkeley, USA
  
  SLAC is developing the Lightsource Unified Modeling Environment (LUME) for efficient modeling of X-ray free electron laser (XFEL) performance. This project takes a holistic approach starting with the simulation of the electron beams, to the production of the photon pulses, to their transport through the optical components of the beamline, to their interaction with the samples and the simulation of the detectors, and finally followed by the analysis of simulated data. LUME leverages existing, well-established simulation codes, and provides standard interfaces to these codes via open-source Python packages. Data are exchanged in standard formats based on openPMD and its extensions. The platform is built with an open, well-documented architecture so that science groups around the world can contribute specific experimental designs and software modules, advancing both their scientific interests and a broader knowledge of the opportunities provided by the exceptional capabilities of X-ray FELs.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB217  
About • paper received ※ 20 May 2021       paper accepted ※ 20 July 2021       issue date ※ 19 August 2021  
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THPAB313 Drive Laser System for Shanghai Soft X-Ray Free Electron Laser laser, electron, cathode, free-electron-laser 4403
 
  • L. Feng, C.L. Li, B. Liu, J.G. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • X. Lu
    ANL, Lemont, Illinois, USA
  • X.T. Wang, W.Y. Zhang
    Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
  
  In this paper, we introduce the design and layout of the drive laser of Shanghai Soft X-ray Free Electron Laser (SXFEL). It is known that the temporal and spatial distribution of the drive laser is crucial for high-quality electron beams. The drive laser provides the laser pulse of 266nm wavelength and 8ps pulse duration for the photocathode, as well as 400nm wavelength, 2-20ps tunable pulse duration for the laser heater. For this purpose, there are mainly four parts in such system, including a third-harmonic generation device, pulse stretcher, image transmitted system, and laser optical module for laser heater. Finally, the measured results of the electron beam under this drive laser system are presented and discussed.  
poster icon Poster THPAB313 [0.691 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB313  
About • paper received ※ 20 May 2021       paper accepted ※ 15 July 2021       issue date ※ 24 August 2021  
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THPAB314 Development of the Femtosecond Timing Distribution System for the Shanghai Soft X-Ray Free Electron Laser timing, laser, FEM, experiment 4406
 
  • L. Feng, C.L. Li, B. Liu, J.G. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • X.T. Wang, W.Y. Zhang
    Shanghai Advanced Research Institute, Pudong, Shanghai, People’s Republic of China
  
  High accuracy timing and synchronization system on femtosecond timescale play an important role for free-electron laser projects such as Shanghai Soft X-ray free-electron laser facility (SXFEL), and future Shanghai high repetition rate XFEL and Extreme light facility (SHINE). To meet the high precision synchronization requirements for both facilities, an optical-based timing distribution system is absolutely necessary. Such a system distributes the laser pulse train from a locked optical master oscillator through the fiber links, which stabilized by a balance optical cross-correlator based on a periodical-poled KTiOPO4 crystal. In this paper, the recent progress and experimental results of SXFEL and SHINE timing distribution system will be reported.  
poster icon Poster THPAB314 [0.351 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB314  
About • paper received ※ 20 May 2021       paper accepted ※ 15 July 2021       issue date ※ 22 August 2021  
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FRXA01 Full Energy On-Demand Beam Injection from SACLA into the SPring-8 Storage Ring injection, electron, operation, linac 4508
 
  • H. Maesaka, T. Fukui, T. Hara, T. Hiraiwa, T. Inagaki, E. Iwai, H. Tanaka, K. Togawa
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • H. Dewa, T. Fujita, K. Fukami, N. Hosoda, A. Kiyomichi, M. Masaki, S. Matsubara, T. Ohshima, M. Oishi, K. Soutome, S. Takano, T. Watanabe
    JASRI/SPring-8, Hyogo-ken, Japan
  • C. Kondo
    JASRI, Hyogo, Japan
  
  The beam injector for the SPring-8 storage ring (SR) was switched from the booster synchrotron to the SACLA linac, a driver for X-ray free-electron laser (XFEL). The low-emittance beam from SACLA (~100 pm rad, 8 GeV) is delivered to the SR through a 600m-long beam transport line. This low-emittance beam can be applied to the new low-emittance storage ring after the SPring-8 upgrade planed in the coming years. The shutdown of the booster synchrotron and 1-GeV linac saves energy consumption and operation cost. To provide the electron beam injected to the SR on demand for the top-up injection during the XFEL operation, the SACLA linac must be synchronized to the desired bucket of the SR, the beam energy and route must be switched shot-to-shot, and the XFEL performance must not be degraded. We developed a precise synchronization system, on-demand beam route and parameter switching system, a pulsed magnet for the switchyard, isolated bunch purification system, etc. In this presentation, we will show the design and performance of each component for the beam injection and the results from beam commissioning of the accelerator and transport line.  
slides icon Slides FRXA01 [3.446 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA01  
About • paper received ※ 19 May 2021       paper accepted ※ 01 July 2021       issue date ※ 31 August 2021  
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FRXA06 Mitigation of Beam Instabilities in the Echo-Enabled Harmonic Generation Beamline for FLASH2020+ bunching, laser, electron, free-electron-laser 4514
 
  • F. Pannek, W. Hillert, D. Samoilenko
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • S. Ackermann, E. Allaria, P. Niknejadi, G. Paraskaki, L. Schaper
    DESY, Hamburg, Germany
  • M.A. Pop
    MAX IV Laboratory, Lund University, Lund, Sweden
  
  With the FLASH2020+ upgrade, one of the beamlines of the free-electron laser FLASH at DESY will be based on the Echo-Enabled Harmonic Generation (EEHG) seeding scheme and provide high-repetition-rate, coherent radiation down to 4 nm. To reach this wavelength, it is necessary to imprint intricate structures on the longitudinal phase space of the electron bunch at a very high harmonic of the seed laser wavelength, making the scheme potentially vulnerable to beam instabilities. Part of the beamline is a strong chicane, which is necessary to create the dispersion required by EEHG. Resulting effects such as Coherent Synchrotron Radiation (CSR) can be very detrimental for the bunching process and have to be taken into account already in the design of the beamline to ensure optimum FEL performance. We investigate and propose possible mitigation solutions to such instabilities in the FLASH2020+ parameter range.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA06  
About • paper received ※ 19 May 2021       paper accepted ※ 20 July 2021       issue date ※ 20 August 2021  
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FRXB07 Injector Optimization for the IR-FEL Operation at the Compact ERL at KEK emittance, gun, operation, laser 4531
 
  • O.A. Tanaka, N. Higashi, T. Miyajima
    KEK, Ibaraki, Japan
  
  Funding: Work supported by NEDO project "Development of advanced laser processing with intelligence based high-brightness and high-efficiency laser technologies (TACMI project)".
The Compact Energy Recovery Linac (cERL) at KEK is a test accelerator to develop ERL technologies and to operate with a high average beam current and a high beam quality. cERL consists of a photoinjector, a main linac for energy recovery, a recirculation loop and a beam dump. A recent upgrade of the cERL to the middle Infrared Free Electron Laser (IR-FEL) imposed new conditions to maintain beam parameters. Therefore, the injector should be optimized to meet the following requirements at the exit of the main linac. The rms bunch length should be 2 ps, the rms longitudinal emittance should be kept the least, and simultaneously the rms transverse emittance should be kept less than 3 c mm mrad. In this work we describe the strategy and results of the injector optimization to achieve the better performance of the cERL-FEL. 		 
slides icon Slides FRXB07 [3.450 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXB07  
About • paper received ※ 19 May 2021       paper accepted ※ 22 July 2021       issue date ※ 14 August 2021  
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FRXC06 Development of the Prototype of the Cavity BPM System for SHINE cavity, experiment, electron, controls 4552
 
  • J. Chen, Y.B. Leng, R.X. Yuan
    SSRF, Shanghai, People’s Republic of China
  • S.S. Cao
    SINAP, Shanghai, People’s Republic of China
  • L.W. Lai
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  
  The Shanghai high repetition rate XFEL and extreme light facility (SHINE) under construction is designed as one of the most advanced FEL facilities in the world, which will produce coherent x-rays with wavelengths from 0.05 to 3 nm and maximum repetition rate of 1MHz. In order to achieve precise, stable alignment of the electron and photo beams in the undulator, the prototype of the cavity beam position monitors (CBPM) including C-band and X-band have been designed and fabricated for the SHINE. And the requirement of the transverse position resolution is better than 200 nm for a single bunch of 100 pC at the dynamic range of ±100 µm. In this paper, we present the design of the cavity with high loaded Q and the RF front-end with low noise-figure, adjustable gain, single-stage down-conversion and phase-locked with reference clock, and also described the structure and specifications of the home-made data acquisition (DAQ) system. The construction of the experiment platform and preliminary measurement result with beam at Shanghai Soft X-ray FEL facility (SXFEL) will be addressed as well.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXC06  
About • paper received ※ 20 May 2021       paper accepted ※ 06 July 2021       issue date ※ 17 August 2021  
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