Electron Accelerators and Applications
FELs
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MO2A01
XFEL Projects in China  
 
  • Z.T. Zhao, D. Wang
    SINAP, Shanghai, People’s Republic of China
 
  840MeV SXFEL is the first soft X-ray FEL built in Shanghai, now it’s in the commissiong stage. Also in Shanghai light source, a Hard X-ray 8GeV CW FEL has been proposed many years ago, and presumably will be approved in 2018.  
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MO2A02
Linac Based Light Source Activities at THU  
 
  • Y. C. Du, L.X. Yan
    TUB, Beijing, People’s Republic of China
 
  The high brightness electron linac based on a photocathode RF gun was established in Tsinghua University for the study of Thomson scattering x-ray and THz radiation light sources. Recent THz radiation research activities with tunable bunch trains, specially on their generation and diagnostics, will be presented. Experiments on coherent undulator radiation, coherent transition radiation, coherent Smith-Purcell radiation, dielectric wakefield radiation were performed. Another part of this talk will be focused on the recent progress in linac based ICS source at Tsinghua University, including the experiments on X/gamma-ray generation, diagnostic, and its applications in advanced X-ray imaging. And the design of a new compact ICS gamma-ray sources will also be discussed in this talk.  
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MO2A04 Compact SRF Linac for High Brilliance Inverse Compton Scattering Light Source 19
 
  • K.E. Deitrick, J.R. Delayen, G.A. Krafft, B. Terzić
    ODU, Norfolk, Virginia, USA
  • J.R. Delayen, G.A. Krafft
    JLab, Newport News, Virginia, USA
 
  New designs for compact SRF linacs can produce micron-size electron beams. These can can be used for inverse Compton scattering light sources of exceptional flux and brilliance.  
slides icon Slides MO2A04 [1.717 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MO2A04  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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MOPO034 Dielectric Waveguide-Based THz Radiator Study for SwissFEL 94
MOOP06   use link to see paper's listing under its alternate paper code  
 
  • L. Shi, S. Bettoni, M.M. Dehler, E. Ferrari, B. Hermann, R. Ischebeck, F. Marcellini, S. Reiche, V.G. Thominet
    PSI, Villigen PSI, Switzerland
  • A.K. Mittelbach
    Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany
 
  Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 701647
THz pulses have many unique properties in terms of radiation matter interaction. In particular their non-ionizing excitation of phonons in matter makes them a preferred pump for pump-probe studies at free electron lasers. In order to enrich the scientific potentials at SwissFEL (Swiss Free Electron Laser), which can provide ultrashort soft and hard X-ray pulses, we plan to build an economic THz radiator in the range of 1-20 THz by passing the spent electron beam through a dielectric lined tube after the electron beam has generated X-rays. These THz pulses will be transported to the photon user station. Since SwissFEL operates with 2 bunches, serving two beamlines, THz from the first bunch can be used at the user station of the second bunch to allow for pump arrival time before the probe. The core of such a THz generation setup is the dielectric lined tube and the relativistic electron beam. This paper reports on the numerical study of these tubes, in terms of mode structure, energy, pulse length etc, which are essential parameters for the pump-probe experiments. These tubes will be fabricated and tested in the near future in the electron beam line for the soft X-ray of SwissFEL.
 
slides icon Slides MOPO034 [1.471 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO034  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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MOPO035 Status of CLARA Front End Commissioning 98
MOOP03   use link to see paper's listing under its alternate paper code  
 
  • D. Angal-Kalinin, A.D. Brynes, S.R. Buckley, P.A. Corlett, L.S. Cowie, K.D. Dumbell, D.J. Dunning, P.C. Hornickel, F. Jackson, J.K. Jones, J.W. McKenzie, B.L. Militsyn, A.J. Moss, T.C.Q. Noakes, M.D. Roper, D.J. Scott, B.J.A. Shepherd, E.W. Snedden, N. Thompson, C. Tollervey, D.A. Walsh, T.M. Weston, A.E. Wheelhouse
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • R.J. Cash, R.F. Clarke, G. Cox, C. Hodgkinson, R.J. Smith, J.T.G. Wilson
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • K.D. Dumbell, B.J.A. Shepherd
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  CLARA (Compact Linear Accelerator for Research and Applications) is a Free Electron Laser (FEL) test facility under development at Daresbury Laboratory. The principal aim of CLARA is to test advanced FEL schemes which can later be implemented on existing and future short wavelength FELs. We report on the commissioning of the CLARA front end, consisting of a photoinjector and the first linac section, and merger into the existing VELA (Versatile Electron Linear Accelerator) beamline.  
slides icon Slides MOPO035 [1.870 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO035  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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MOPO036 Status of the 10 MW MBKs during Commissioning of the European XFEL in DESY 102
MOOP04   use link to see paper's listing under its alternate paper code  
 
  • V. Vogel (Fogel), Ł. Butkowski, A. Cherepenko, S. Choroba, J. Hartung
    DESY, Hamburg, Germany
 
  At present 26 RF stations for European XFEL are in operation. Each of the RF stations consists of a HV modulator located in a separate building on the DESY campus, up to 1600 m long 10 kV HV cables that connect the modulator and the HV pulse transformer located in the underground tunnel, 120kV, 3 m long HV cable connecting the HV pulse transformer and the connection module of the horizontal multi-beam klystron. Two RF stations of the injector have already achieved about 20000 hours of operation, RF stations of the XFEL bunch compressor area have operated up to 11000 hours and in the XFEL main linac up to 8000 hours. To increase the lifetime of the klystrons, we use a fast protection system (KLM) that is based on the comparison of the actual RF shape and the expected RF shape. In the case of a difference exceeding a certain margin, for example, in the case of RF breakdown in a klystron or RF breakdown in a waveguide system, the KLM quickly, shorter than 500 ns, switches off the input RF signal. Thus, it does prevents the vacuum level in the klystron worsen too much or it minimizes the RF overvoltage time at the output windows of the klystron in case of breakdown in waveguides.  
slides icon Slides MOPO036 [5.241 MB]  
poster icon Poster MOPO036 [0.658 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO036  
About • paper received ※ 05 September 2018      issue date ※ 18 January 2019  
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MOPO037 SRF Gun Development at DESY 105
MOOP07   use link to see paper's listing under its alternate paper code  
 
  • E. Vogel, S. Barbanotti, I. Hartl, K. Jensch, D. Klinke, D. Kostin, W.-D. Möller, M. Schmökel, J.K. Sekutowicz, S. Sievers, N. Steinhau-Kühl, A.A. Sulimov, J.H. Thie, H. Weise, L. Winkelmann, B. van der Horst
    DESY, Hamburg, Germany
  • J.A. Lorkiewicz, R. Nietubyć
    NCBJ, Świerk/Otwock, Poland
  • J. Smedley
    BNL, Upton, Long Island, New York, USA
  • J. Teichert
    HZDR, Dresden, Germany
  • M. Wiencek
    IFJ-PAN, Kraków, Poland
 
  A future upgrade of the European XFEL (E-XFEL) foresees an additional cw operation mode increasing the flexibility in the photon beam time structure. This mode requires among others a cw operating photo injector. We believe that using an SRF gun is the preferred approach as the beam parameters of normal conducting pulsed guns can be potentially met by SRF guns operating cw. Since more than a decade DESY in collaboration with TJNAF, NCBJ, BNL, HZB and HZDR performs R&D to develop an all superconducting RF gun with a lead cathode. In the frame of E-XFEL cw upgrade feasibility studies, the SRF-gun R&D program gained more attention and support. Within the next few years we would like to demonstrate the performance of the all superconducting injector required for the E-XFEL upgrade. The selected approach offers advantages w.r.t. the cleanliness of the superconducting surface, but requires a complete disassembly of a cryostat and stripping the gun cavity in a clean room to exchange the cathode. Thus it is practical only when the life time of the cathode is at least several months. In this paper we present the actual status of the R&D program, next steps and the longer term plans.  
slides icon Slides MOPO037 [1.966 MB]  
poster icon Poster MOPO037 [3.774 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO037  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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MOPO038 RF Operation Experience at the European XFEL 109
MOOP09   use link to see paper's listing under its alternate paper code  
 
  • J. Branlard, V. Ayvazyan, Ł. Butkowski, M.K. Grecki, M. Hierholzer, M.G. Hoffmann, M. Hoffmann, M. Killenberg, D. Kostin, T. Lamb, L. Lilje, U. Mavrič, M. Omet, S. Pfeiffer, R. Rybaniec, H. Schlarb, Ch. Schmidt, N. Shehzad, V. Vogel, N. Walker
    DESY, Hamburg, Germany
 
  After its successful commissioning which took place during the first half of 2017, the European X-ray free electron laser is in now in regular operation delivering photons to users since September 2017. This paper presents an overview on the experience gathered during the first couple of years of operation. In particular, the focus is set on RF operation, maintenance activities, availability and typical failures. A first look on machine performance in terms of RF and beam stability, energy reach, radiation related investigations and microphonics studies will also be presented.  
slides icon Slides MOPO038 [2.421 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO038  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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MOPO039 Status Update of the Fast Energy Corrector Cavity at FLASH 112
 
  • S. Pfeiffer, J. Branlard, Ł. Butkowski, M. Hierholzer, M. Hoffmann, K. Honkavaara, H. Schlarb, Ch. Schmidt, S. Schreiber, M. Vogt, J. Zemella
    DESY, Hamburg, Germany
  • M. Fakhari
    CFEL, Hamburg, Germany
 
  Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453.
Linear accelerator facilities driving a free-electron laser require femtosecond precision synchronization between external laser systems and the electron beam. Such high precision is required for pump-probe experiments and also for example for the electron bunch injection into a plasma bubble for laser plasma acceleration. An upgrade of the fast intra-train beam-based feedback system is planned at the Free-Electron Laser FLASH in Hamburg, Germany. This linear accelerator is based on superconducting (SRF) technology operating with pulse trains of maximum 1 MHz bunch repetition rate. Arrival time fluctuations of the electron beam are correctable by introducing small energy modulations prior to the magnetic bunch compressor. This contribution focuses on the design and the characterization of a normal-conducting RF (NRF) cavity with large bandwidth, mandatory to correct fast arrival time fluctuations. The cavity has recently been installed in the FLASH beamline. First measurements with the new cavity will be presented.
 
poster icon Poster MOPO039 [1.884 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO039  
About • paper received ※ 13 September 2018      issue date ※ 18 January 2019  
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MOPO040 Coherent Synchrotron Radiation Monitor for Microbunching Instability in XFEL 115
MOOP05   use link to see paper's listing under its alternate paper code  
SPWR002   use link to see paper's listing under its alternate paper code  
 
  • J.H. Ko, I.S. Ko
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  • H.-S. Kang, C. Kim, G. Kim
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  The microbunching instability is an important issue in an X-ray Free Electron Laser (XFEL). The intensity of the FEL can be reduced significantly by the microbunching instability so that the laser heater is widely used to reduce it. In the X-ray Free Electron Laser of the Pohang Accelerator Laboratory (PAL-XFEL), to directly monitor the microbunching instability, a visible CCD camera was included into the coherent radiation monitor (CRM) which uses a pyroelectric detector. It enabled us to measure the microbunching instability more clearly and optimize the FEL lasing in the PAL-XFEL.  
slides icon Slides MOPO040 [1.125 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO040  
About • paper received ※ 11 September 2018      issue date ※ 18 January 2019  
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MOPO041 Performance Test Results of Magnet Power Supply 118
 
  • K.-H. Park, J.H. Han, S.-H. Jeong, Y.G. Jung, D.E. Kim, M.J. Kim, H.-G. Lee, S.B. Lee, B.G. Oh, H.S. Suh
    PAL, Pohang, Kyungbuk, Republic of Korea
 
  A high stable magnet power supply (MPS) was developed, which was a bipolar type with 200A of the output current at the 40V of output voltage. The MPS has been implemented by the digital signal processing technology using the DSP, FPGA, ADCs and so on. The output current stability of the MPS showed about 6ppm peak-to-peak in a short term experiment at 200A of its full output current. The long term stability was shown in 15 ppm peak-to-peak for 10 hours at 200A. And the others experimental results about the MPS were shown in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO041  
About • paper received ※ 31 August 2018      issue date ※ 18 January 2019  
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MOPO042 Evolutionary Many-objective Optimization Algorithm for Large-bandwidth Free-Electron-Laser Generation 121
SPWR003   use link to see paper's listing under its alternate paper code  
 
  • J.W. Yan, H.X. Deng
    SINAP, Shanghai, People’s Republic of China
 
  Funding: National Natural Science Foundation of China , the National Key Research and Development Program of China, the Young Elite Scientist Sponsorship Program by CAST and Ten Thousand Talent Program.
X-ray free-electron lasers (XFELs) are leading-edge instruments in a wide range of research fields. Besides pursuing narrow bandwidth FEL pulses, the large-bandwidth XFEL pulses are very useful in various spectroscopy experiments, multi-wavelength anomalous diffraction, and X-ray crystallography. Overcompression operation scheme can be utilized to generate electron beams with large energy chirp which is benefit for bandwidth broadening. Recently, an evolutionary many-objective (having four or more objectives) algorithm, NSGA-III, was used to optimize the electron beam parameters in the overcompression including energy chirp, energy spread, current profile, peak current, and projected emittance. In this paper, combining with the Xie’s semianalytical estimate formula, the NSGA-III is utilized to find an optimal working point of linac by optimizing the XFEL pulse properties directly. Start-to-end numerical simulations based on the Shanghai soft X-ray Free-Electron Laser user facility parameters demonstrate that a full bandwidth of 4.75% can be generated.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO042  
About • paper received ※ 12 September 2018      issue date ※ 18 January 2019  
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WE1A05 SwissFEL Linac Commissioning Status, Current Performance and Future Plans 605
 
  • P. Craievich
    PSI, Villigen PSI, Switzerland
 
  SwissFEL, the hard x-ray free-electron laser facility at PSI, is in an advanced commissioning phase. The commissioning of the 5.8 GeV Linac started in 2016 and the first FEL pilot-experiments were performed at a reduced beam energy in the end of 2017. In 2018, it is foreseen to progressively increase the electron beam energy and photon energy up to the maximum design values, interleaved by several FEL pilot experiments. This paper gives an overview of the commissioning progress including the achieved machine performance and first operational experience.  
slides icon Slides WE1A05 [10.370 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-WE1A05  
About • paper received ※ 18 September 2018      issue date ※ 18 January 2019  
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FR2A02 Commissioning of the European XFEL 994
 
  • D. Nölle
    DESY, Hamburg, Germany
 
  The construction of the European XFEL has been finished at the end of 2016 and commissioning has been started. Meanwhile the entire facility, driving 3 free-electron-lasers in the hard and soft X-ray regime, is in operation. This contribution will report on commissioning and transition to operation, as well as on the first user runs.  
slides icon Slides FR2A02 [11.022 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-FR2A02  
About • paper received ※ 04 September 2018      issue date ※ 18 January 2019  
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