MC2: Photon Sources and Electron Accelerators
A06 Free Electron Lasers
Paper Title Page
MOPAB018 SASE Gain-Curve Measurements with MCP-Based Detectors at the European XFEL 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 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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MOPAB054 Start-to-End Simulation of a Free-Electron Laser Driven by a Laser-Plasma Wakefield Accelerator 233
 
  • W. Liu, Y. Jiao, S. Wang
    IHEP, Beijing, People’s Republic of China
 
  The rapid development of laser-plasma wakefield accelerator (LPA) has opened up a new possible way to achieve ultra-compact free-electron laser (FEL). To this end, LPA experts have made many efforts to generate electron beams with sub-micrometer emittance and low energy spread. Recently, a new laser modulation method was proposed for generating EUV coherent pulse in an LPA-driven FEL. The simulation demonstration of this scheme is based on the Gaussian beam. However, the distribution of the LPA beam is not Gaussian. To further verify the feasibility of the method mentioned above, a start-to-end simulation is required.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB054  
About • paper received ※ 18 May 2021       paper accepted ※ 27 May 2021       issue date ※ 22 August 2021  
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MOPAB066 Dual Octupole Emittance Growth Correction of the CompactLight XFEL Bunch Compressors 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 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 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 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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MOPAB266 Start-to-End Study on Laser and RF Jitter Effects for MAX-IV SXL 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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TUPAB067 Production of 120 MeV Gamma-ray Beams at Duke FEL and HIGS Facility 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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TUPAB069 The Sabina Terahertz/Infrared Beamline at SPARC-Lab Facility 1525
 
  • S. Macis
    La Sapienza University of Rome, Rome, Italy
  • M. Bellaveglia, M. Cestelli Guidi, E. Chiadroni, F. Dipace, 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
  • V. Petrillo
    INFN-Milano, Milano, Italy
 
  Funding: SABINA is a project co-funded by Regione Lazio within POR-FESR 2014-2020 program.
Following the EU Terahertz (THz) Road Map*, high-intensity, ps-long, THz)/Infrared (IR) radiation is going to become a fundamental spectroscopy tool for probing and control low-energy quantum systems ranging from graphene, and Topological Insulators, to novel superconductors** ***. In the framework of the SABINA project, a novel THz/IR beamline based on an APPLE-X undulator emission will be developed at the SPARC-Lab facility at LNF-INFN. Light will be propagated from the SPARC-Lab to a new user lab facility nearly 20 m far away. This beamline will cover a broad spectral region from 3 THz to 30 THz, showing ps- pulses and energy of tens of µJ with variable polarization from linear to circular. The corresponding electric fields up to 10 MV/cm, are able to induce non-linear phenomena in many quantum systems. The beamline, open to user experiments, will be equipped with a 5 T magnetic cryostat and will be synchronized with a fs laser for THz/IR pump, VIS/UV probe experiments.
[*] S.S. Dhillon et al., J. Phys. D: Appl. Phys. 50, 043001 (2017);
[**] F. Giorgianni et al., Nature Commun. 7, 11421 (2016);
[***] P. Di Pietro et al., Phys. Rev. Lett. 124, 226403 (2020);
 
poster icon Poster TUPAB069 [0.884 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB069  
About • paper received ※ 16 May 2021       paper accepted ※ 21 June 2021       issue date ※ 25 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 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 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 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 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 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.
 
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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 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 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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TUPAB081 Design of the Beam Distribution System of SHINE 1562
 
  • S. Chen, M. Gu, R. Wang
    SSRF, Shanghai, People’s Republic of China
  • H.X. Deng, X. Fu
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
 
  In shanghai, a hard X-ray free electron laser project named SHINE is under design. It will be based on a superconducting linac running in CW mode. On the first stage, there will be three parallel undulator lines downstream the linac. For simultaneous operation of the three undulator lines, a beam distribution system based on fast kickers will be installed between linac and undulator lines. The physics design of this beam distribution system is described in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB081  
About • paper received ※ 19 May 2021       paper accepted ※ 14 June 2021       issue date ※ 22 August 2021  
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TUPAB082 Analysis of the Effect of Energy Chirp in Implementing EEHG at SXL 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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TUPAB083 Dual Energies in the LCLS Copper Linac 1570
 
  • F.-J. Decker, C. Bianchini Mattison, D.K. Bohler, A. Brachmann, W.S. Colocho, S. Condamoor, M.L. Gibbs, K.H. Kim, A.A. Lutman, T.J. Maxwell, J.A. Mock, H.-D. Nuhn, J.C. Sheppard, H. Smith, T.J. Smith, M. Stanek, S. Zelazny, Z. Zhang, C.M. Zimmer
    SLAC, Menlo Park, California, USA
 
  For LCLS-II two undulators were installed at SLAC, one for soft and one for hard x-rays. Before the superconducting linac gets turned on the copper linac is providing beams at 120 Hz to these two beam destinations. The 120 Hz can be split in many different ratios between soft and hard via a pulsed magnet. To get an optimized beam for the quite different photon energies the pulsed linac components like modulators and RF can provide many different beam parameters, mainly energies and bunch lengths for the two undulator lines. How this was implemented with timing setups of triggers and finally after the split the necessary matching of the transverse phase space will be discussed.  
poster icon Poster TUPAB083 [0.479 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB083  
About • paper received ※ 19 May 2021       paper accepted ※ 27 May 2021       issue date ※ 21 August 2021  
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TUPAB084 An Empirically-Derived ABCD Matrix for Transverse Dynamics Studies in Seeded Free-Electron Lasers 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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TUPAB086 FLASH2020+ Plans for a New Coherent Source at DESY 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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TUPAB087 Full Characterization of the Bunch-Compressor Dipoles for FLUTE 1585
 
  • Y. Nie, A. Bernhard, E. Bründermann, A.-S. Müller, M.J. Nasse, R. Ruprecht, J. Schäfer, M. Schuh, Y. Tong
    KIT, Karlsruhe, Germany
 
  Funding: This work is supported by the BMBF project 05H18VKRB1 HIRING (Federal Ministry of Education and Research).
The Ferninfrarot Linac- Und Test-Experiment (FLUTE) is a KIT-operated linac-based test facility for accelerator research and development as well as a compact, ultra-broadband and short-pulse terahertz (THz) source. As a key component of FLUTE, the bunch compressor (chicane) consisting of four specially designed dipoles will be used to compress the 40-50 MeV electron bunches after the linac down to single fs bunch length. The maximum vertical magnetic field of the dipoles reach 0.22 T, with an effective length of 200 mm. The good field region is ±40 mm and ±10.5 mm in the horizontal and vertical direction, respectively. The latest measurement results of the dipoles in terms of field homogeneity, excitation and field reproducibility within the good field regions will be reported, which meet the predefined specifications. The measured 3D magnetic field distributions have been used to perform beam dynamics simulations of the bunch compressor. Effects of the real field properties on the beam dynamics, which are different from that of the ASTRA built-in dipole field, will be discussed.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB087  
About • paper received ※ 10 May 2021       paper accepted ※ 27 May 2021       issue date ※ 01 September 2021  
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TUPAB089 Proof-of-Principle Experiment Design for PEHG-FEL in SXFEL User Facility 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 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 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 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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TUPAB101 Monte Carlo Simulations and Neutron and Gamma Fluence Measurements to Investigate Stray Radiation in the European XFEL Undulator System 1615
 
  • O.E. Falowska-Pietrzak, A. Hedqvist, F. Hellberg
    Stockholm University, Stockholm, Sweden
  • N. Bassler
    DCPT, Aarhus N, Denmark
  • A. Leuschner, D. Nölle
    DESY, Hamburg, Germany
  • F. Wolff-Fabris
    EuXFEL, Schenefeld, Germany
 
  The European X-ray Free Electron Laser (XFEL) is an user facility research centre generating extremely bright and ultra-short SASE x-ray pulses. The laser flashes are generated when electrons of GeV energies pass the undulator systems. Even if the dominating contribution of the radiation field in the undulator is from spontaneous undulator radiation, also electron losses can be observed, e.g. during beam steering or due to beam halo, not captured by the upstream collimation system. The interactions of those particles with the vacuum vessel wall result in the emission of stray radiation. The LB 6419 detector allows to measure both the neutron and the gamma component in the pulsed radiation fields nearby the undulators*. Usually, the real-time measurements show the dominance of the gamma signals. However, in case of particle loss occurs, a neutron signal is observed. In addition, Monte Carlo (MC) simulations conducted using the Geant4 code indicate that neutrons are also present within the undulator’s magnets volume. In this work, we present the LB 6419 measurement data and compare these to our MC simulations, to characterize the radiation field nearby the undulator segment.
* KLETT, A., LEUSCHNER, A., TESCH, N., A dose meter for pulsed neutron fields, Radiat Meas 45 (2010) 1242-1244
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB101  
About • paper received ※ 19 May 2021       paper accepted ※ 02 June 2021       issue date ※ 18 August 2021  
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TUPAB102 A New 2nd Bunch Compression Chicane for the FLASH2020+ Project 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 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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TUPAB104 Redesign of the FLASH2 Post-SASE Undulator Beamline 1626
 
  • F. Christie, J. Rönsch-Schulenburg, S. Schreiber, M. Vogt, J. Zemella
    DESY, Hamburg, Germany
 
  FLASH2 is one of the two SASE (Self-Amplified Spontaneous Emission) undulator beamlines lines comprising variable gap undulators to produce radiation in the XUV and soft X-ray regime at FLASH. Downstream of the SASE undulators the beamline is currently undergoing a major redesign. During shutdowns in summer 2020 and winter 2021 two PolariX TDSs (Polarizable X-band Transverse Deflecting Structure) were installed, as well as additional diagnostics, to monitor the longitudinal phase space density of the electron bunches. Additionally, an afterburner undulator will be integrated in the next shutdown to produce circularly polarized light with wavelengths down to 1.39 nm. In this paper, we will present the modifications that were and will be made to the electron beamline in the course of this redesign.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB104  
About • paper received ※ 19 May 2021       paper accepted ※ 21 July 2021       issue date ※ 23 August 2021  
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TUPAB105 Simulation Studies for Dark Current Signature From DLS RF Gun 1630
 
  • J. Karmakar, M. Aggarwal, S. Ghosh, B. Karmakar, P. Patra, B.K. Sahu, A. Sharma
    IUAC, New Delhi, India
 
  The Delhi Light source (DLS) is an upcoming compact THz facility at IUAC, New Delhi, based on pre-bunched FEL. RF conditioning of the 2.6 cell S-band RF gun is presently carried out with a Cu photo-cathode (PC) plug and dark current is produced when substantial accelerating field is reached inside the cavity. To identify the possible field emission sites contributing to dark current, single electron ASTRA simulations are done with a phase scan of the RF field. The simulation is extended to include multi-particle emission from the PC edge as a ring. The energies present in the dark current is analysed from the the Fowler Nordheim current plot and energy phase scan plot. The distribution of few dark current energies and their respective trajectories upto the YAG screen at a given solenoid setting is traced and shown in the simulations. We also present the dark current images captured during the initial RF conditioning and try to compare it with the simulations.  
poster icon Poster TUPAB105 [0.742 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB105  
About • paper received ※ 19 May 2021       paper accepted ※ 17 August 2021       issue date ※ 01 September 2021  
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TUPAB106 Simulation Calculations of Compact THz Facility at IUAC, New Delhi 1633
 
  • J. Karmakar, S. Ghosh
    IUAC, New Delhi, India
 
  A compact THz radiation source based on the principle of pre-bunched Free Electron Laser is at the commissioning stage at Inter University Accelerator Centre (IUAC), New Delhi. The facility will generate low emittance train of electron micro-bunches (2, 4, 8 or 16 numbers) from a RF photo-cathode gun in the energy range of 4 to 8 MeV and inject into a compact undulator to generate coherent THz radiation in the frequency range of ~0.18 to 3.0 THz. To optimize the intensity at a given frequency, the beam bunching factor and the betatron oscillation amplitude in the non-wiggling plane of the electronμbunches inside the undulator has been maximized and minimized respectively. The paper presents the optimized beam optics simulation results for two frequencies viz 0.5 and 2 THz. The on-axis radiation spectral intensity computed by in-house developed code using the trajectory data of the beam optics simulation is also presented for the two frequencies.  
poster icon Poster TUPAB106 [1.208 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB106  
About • paper received ※ 18 May 2021       paper accepted ※ 31 August 2021       issue date ※ 12 August 2021  
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TUPAB107 Accelerator and Light Source Research Program at Duke University 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 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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TUPAB111 Layout of the Laser Heater for FLASH2020+ 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 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. 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 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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TUPAB116 Toward THz Coherent Undulator Radiation Experiment with a Combination of Velocity Bunchings 1663
 
  • Y. Sumitomo, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, T. Tanaka
    LEBRA, Funabashi, Japan
 
  Funding: Japan Society for the Promotion of Science (JSPS), Grant-in-Aid for Scientific Research (KAKENHI), Grant Number JP19K12631.
We have launched a research program to generate the THz coherent undulator radiations, following the proposal of the combination of velocity bunchings * at Nihon University. The combination of velocity bunchings is an efficient way of bunch compression allowing a range of energy choices, in other words, a range of quasi-monochromatic radiation wavelengths generated at the undulator. In addition to the existing wideband THz light sources (0.1 - 2 THz) by the coherent edge and transition radiations currently available at Nihon Univ., the development of a high peak-power and quasi-monochromatic coherent radiation should accelerate the activities including the material science related to the THz bandwidths. In this presentation, we illustrate the program and report the current status of the experiment.
* Y. Sumitomo et al., J. Phys. Conf. Ser., vol. 1067, p. 032017, 2018.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB116  
About • paper received ※ 19 May 2021       paper accepted ※ 15 June 2021       issue date ※ 15 August 2021  
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TUPAB117 Eigenmode Decomposition for Free-Electron Lasers Using Bayesian Analysis 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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TUPAB121 Photoinjector Drive Laser Temporal Shaping for Shanghai Soft X-Ray Free Electron Laser 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 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 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 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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TUPAB127 Spare Gun Multi-Physics Analysis for LCLS-II 1688
 
  • L. Xiao, C. Adolphsen, A. Cedillo, E.N. Jongewaard, X. Liu, C.-K. Ng, F. Zhou
    SLAC, Menlo Park, California, USA
 
  LBNL APEX VHF normal conducting gun was adopted for LCLS-II CW operation to provide ultra-bright high repetition rate X-ray pulses. The initial LCLS-II gun and injector commissioning showed excessive dark current dominated by field emission around the cathode plug outer diameter and the gun cavity nose. There is a concern that the dark current may get worse with time of operation. It is planning to build a spare rf gun largely based on the current LCLS-II gun to replace current LCLS-II gun. The proposed spare gun has a reduced the peak electrical fields around the cathode plug corner and cavity nose by 10% through further optimizing APEX gun cavity shape. In addition, there are some moderate modifications on the engineering design to increase mechanical robustness and vacuum performance. SLAC developed parallel finite-element electromagnetic code suite ACE3P is used to apply for the spare gun modeling including RF, thermal and structural analysis at static and transient states to ensure its successful operation in LCLS-II. In this paper, the spare gun multi-physics analysis is described.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB127  
About • paper received ※ 19 May 2021       paper accepted ※ 25 August 2021       issue date ※ 12 August 2021  
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WEXC01
Generation of High-Brightness Self-Seeded X-Ray Free Electron Laser  
 
  • C.-K. Min
    PAL, Pohang, Republic of Korea
 
  At the PAL-XFEL, we demonstrate substantially improved self-seeded XFEL performance, which promises to add another popular XFEL operation mode with up to ~mJ pulse energy at 9.7 keV (peak spectral brightness, 3.2×1035 photons s-1 mm-2 mrad-2 (0.1%BW)-1) and wide tunability (3.5-14.6 keV). The machine is tuned to get stable seeding and its monochromatic amplification process and provide a stable amplitude (better than filtered SASE using DCM) and the time-bandwidth product is close to transform-limited. The suppression ofμbunching instability using a laser heater is much more effective in this narrow spectral bandwidth compared to SASE mode with a broad spectrum. The benefit of this seeded XFEL is demonstrated in serial femtosecond crystallography experiments.  
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WEXC02
Enhanced Seeded Free Electron Laser Performance with a "Cold" Electron Beam  
 
  • G. Penco
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
 
  In a seeded free-electron laser operating in high gain harmonic generation (HGHG) as FERMI, the harmonic conversion efficiency decreases at high harmonics and the quality of the pulses is increasingly affected by the electron beam phase space distortions. The lower the electron time-slice energy spread the higher harmonic of the seed is efficiently obtained. The optimization of the FERMI photoinjector and of some linac parameters has allowed a reduction of the relative slice energy spread to the level of few times of 105. With these new conditions, the FEL can be operated without the need for a laser heater to suppress micro-bunching instabilities and this "cold" beam has allowed the generation of extreme UV pulses with pulse energy exceeding 1 mJ, and with peak power of about 10 GW. We describe the electron beam characterization and the FEL performance improvement, including the extension of the range of harmonics of the seed which can be amplified, up to the twenty-fifth harmonic, i.e., 10 nm.  
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THXB07 Coherent Radiation From Inverse Compton Scattering Sources by Means of Particle Trapping 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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THPAB120 Beam on Demand for High-Repetition-Rate X-Ray Free-Electron Lasers 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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FRXA07
Ringdown Measured in a Four-Bounce, 20 Meter Hard X-Ray Cavity  
 
  • J.P. MacArthur, Z. Huang, J. Krzywiński, G. Marcus, R.A. Margraf, T. Sato, D. Zhu
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by the Department of Energy under contract DE-AC02-76SF00515
A cavity-based hard x-ray free-electron laser (CBXFEL) could produce fully coherent pulses with a bandwidth several orders of magnitude below the intrinsic bandwidth of SASE. A cavity-based FEL is not a new concept - the first FEL was an oscillator operating at 3.4 um - but single-pass amplification of spontaneous radiation was the fastest path to gigawatt x-ray powers. One unproven component of a CBXFEL is a stable, high reflectivity cavity. To address this deficit we present ring-down measurements in a 20 m round-trip cold cavity operating at 9.8 keV. The cavity is composed of four strain-relief-cut diamond 400 Bragg mirrors and a transmission grating for in/out-coupling. It is a testbed for alignment protocols and component performance under realistic experimental conditions like source instability, optics imperfections, and thermal drift.
 
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