Keyword: FEL
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MOPO019 Study on Cleaning of Copper Plated Bellows for LCLS-II cavity, SRF, cryomodule, experiment 71
 
  • L. Zhao, E. Daly, G.K. Davis, G.V. Eremeev, A.V. Reilly, A-M. Valente-Feliciano, K.M. Wilson
    JLab, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts DE-AC05-06OR23177 and DE-AC02-76SF00515 for the LCLS-II Project.
Inter-cavity copper plated bellows are part of the LCLS-II cryomodule beamline components. Since the bellows are close to superconducting radio frequency (SRF) cavities during accelerator operation, it is desirable that these bellows have similar cleanliness as SRF cavi-ties. Studies have been done to help evaluate bellows interior cleanliness after the standard bellows cleaning procedure at Jefferson Lab. 		 
poster icon Poster MOPO019 [1.326 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO019  
About • paper received ※ 28 August 2018       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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MOPO024 Development of High Power Coherent Terahertz Wave Sources at Lebra 125 MeV Linac in Nihon University electron, radiation, linac, undulator 78
 
  • T. Sakai, K. Hayakawa, Y. Hayakawa, K. Nogami, Y. Sumitomo, Y. Takahashi, T. Tanaka
    LEBRA, Funabashi, Japan
  • H. Ogawa, N. Sei
    AIST, Tsukuba, Ibaraki, Japan
  
  Funding: This work was supported by JSPS KAKENHI Grant Number JP16K17539 and JP16H03912.
Research and Development of a high performance electron linac for the generation of FEL, Parametric X-ray Radiation (PXR) and THz waves has been continued at the Laboratory for Electron Beam Research and Application (LEBRA) of Nihon University as a joint research with KEK and National Institute of Advanced Industrial Science and Technology. The transport systems of the THz wave were installed in the vacuum chamber on the downstream side of the bending magnet of the PXR and FEL beam-line. The CER and the CSR are generated by the bending magnet each of the beam line. In addition, the CTR using thin metal foil is also generated. The average power of the CTR wave was measured approximately 1 mJ/macro-pulse (pulse width 4.5 µs) near the CTR wave beam source point in the frequency range of 0.1 - 2.5 THz. In addition, the energy of the CER as high as 0.2 mJ/macro-pulse were achieved with the experimental room. Furthermore, CER of the generated the FEL beam line can also be guided from the bending magnet on the downstream side of the undulator without disturbing the FEL oscillations. THz transport beam-lines and the characteristics of the THz waves are discussed in this report. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO024  
About • paper received ※ 12 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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MOPO034 Dielectric Waveguide-Based THz Radiator Study for SwissFEL electron, experiment, radiation, GUI 94
 
  • 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       paper accepted ※ 21 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 klystron, operation, gun, cathode 102
 
  • V. Vogel (Fogel), L. 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       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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MOPO038 RF Operation Experience at the European XFEL cavity, MMI, operation, LLRF 109
 
  • J. Branlard, V. Ayvazyan, L. 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       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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MOPO040 Coherent Synchrotron Radiation Monitor for Microbunching Instability in XFEL radiation, laser, bunching, electron 115
 
  • 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       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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MOPO042 Evolutionary Many-objective Optimization Algorithm for Large-bandwidth Free-Electron-Laser Generation electron, free-electron-laser, laser, linac 121
 
  • 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       paper accepted ※ 21 September 2018       issue date ※ 18 January 2019  
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MOPO073 Coherent Edge Radiation Sources in Linac-Based Infrared Free-Electron Laser Facilities electron, radiation, undulator, cavity 154
 
  • N. Sei, H. Ogawa
    AIST, Tsukuba, Ibaraki, Japan
  • K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Sumitomo, T. Tanaka
    LEBRA, Funabashi, Japan
  • H. Ohgaki, H. Zen
    Kyoto University, Kyoto, Japan
  
  Funding: This study was financially supported by JSPS KAKENHI Grant Number JP16H03912.
National Institute of Advanced Industrial Science and Technology has been studied far-infrared coherent radiation at Linac-based infrared free-electron laser (FEL) facilities in col-laboration with Nihon University and Kyoto University. To obtain high FEL gain at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University and at Kyoto Uni-versity Free Electron Laser (KU-FEL), the electron-bunch length is compressed to less than 1 ps in their undulator sections. Short electron bunches are suitable for generating intense coher-ent radiation, and we have already developed some terahertz-wave sources based on the coher-ent synchrotron radiation and the coherent transition radiation [1-3]. However, it was difficult to observe them with sufficient intensity without disturbing the infrared FEL oscillations. Then, we now develop coherent edge radiation emitted from downstream bending magnets in the un-dulator sections. It can be extracted from the undulator sections without disturbing the FEL os-cillations. In this presentation, the observed coherent radiation at LEBRA and KU-FEL will be reported on.
[1] N. Sei et al., J. Phys. D: Appl. Phys. 46, (2013) 045104.
[2] N. Sei et al., Nucl. Instr. and Meth. A, 832, (2016) 208.
[3] N. Sei et al., Jpn. J. Appl. Phys.: 56, (2017) 032401.
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO073  
About • paper received ※ 29 August 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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MOPO104 LLRF R&D Towards CW Operation of the European XFEL cavity, controls, LLRF, resonance 223
 
  • A. Bellandi, V. Ayvazyan, J. Branlard, C. Gumus, S. Pfeiffer, K.P. Przygoda, R. Rybaniec, H. Schlarb, Ch. Schmidt, J.K. Sekutowicz
    DESY, Hamburg, Germany
  • W. Cichalewski
    TUL-DMCS, Łódź, Poland
  
  The ever growing request for machines with a higher average beam pulse rate and also with a relaxed (< 1 MHz) pulse separation calls for superconducting linacs that operate in Long Pulse (LP) or Continuous Wave (CW) mode. For this purpose the European X-ray Free Electron Laser (European XFEL) could be upgraded to add the ability to run in CW/LP mode. Cryo Module Test Bench (CMTB) is a facility used to perform tests on superconducting cavity cryomodules. Because of the interest in upgrading European XFEL to a CW machine, CMTB is now used to perform studies on XM-3, a 1.3 GHz European XFEL-like cryomodule with modified coupling that is able to run with very high quality factor (QL = 10E7…10E8) values. The RF power source allows running the cavities at gradients larger than 16 MV/m. Because of the QL and gradient values involved in these tests, detuning effects like mechanical resonances and microphonics became more challenging to regulate. The goal is then to determine the appropriate set of parameters for the LLRF control system to keep the error to be less than 0.01° in phase and 0.01% in amplitude.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO104  
About • paper received ※ 11 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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MOPO118 Optimized Design for a Compact Linac with Collinear Absorbing Loads at the Hust FEL-THz cavity, linac, radiation, electron 242
 
  • J. Jiang, G. Feng, T. Hu, Y. Lu, X.D. Tu, Y.Q. Xiong
    HUST, Wuhan, People’s Republic of China
  • Y.J. Pei
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
  
  To meet the requirement of miniaturization for high power THz radiation in the field of commercial and civil use, RF Linacs have been applied widely as beam injectors, and the Linac with collinear absorbing loads reveals the potential to achieve a tradeoff between performance and compactness. Under overall consideration of systematic conflicts, optimization choices for such Linacs involving power absorbing ability, accelerating efficiency, as well as beamline length were described in this context. Meanwhile, cold testing has been conducted to verify design parameters for the collinear absorbing loads. Furthermore, elaborated calculation of thermal power loss and integrated helical water channel cooling has been performed for the 14MeV Linac with collinear absorbing loads installed on the HUST FEL-THz, and online experiments demonstrated that both the accelerating efficiency and the water cooling performance fulfilled operation demands.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO118  
About • paper received ※ 11 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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MOPO121 Large-Scale Optical Synchronization System of the European XFEL laser, timing, experiment, electron 253
 
  • J.M. Müller, M. Felber, T. Kozak, T. Lamb, H. Schlarb, S. Schulz, C. Sydlo, M. Titberidze, F. Zummack
    DESY, Hamburg, Germany
  
  At the European XFEL, a facility-wide optical synchronization system providing a femtosecond-stable timing reference at more than 40 end-stations had been developed and installed. The system is based on an ultra-stable, low-noise laser oscillator, whose signals are distributed via actively length-stabilized optical fibers to the different locations across the accelerator and experimental areas. There, it is used to locally re-synchronize radio frequency signals, to precisely measure the arrival time of the electron beam for fast beam-based feedbacks, and to phase-lock optical laser systems for electron bunch generation, beam diagnostics and user pump-probe experiments with femtosecond temporal resolution. In this paper, we present the system’s architecture and discuss design choices to realize an extensible, large-scale synchronization infrastructure for accelerators that meets reliability, maintainability as well as the performance requirements. Furthermore, the latest performance result of an all-optically synchronized laser oscillator is shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO121  
About • paper received ※ 12 September 2018       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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MOPO122 European XFEL Cooling and Ventilation Systems undulator, photon, controls, electron 257
 
  • J.-P. Jensen
    DESY, Hamburg, Germany
  
  The European Free Electron Laser XFEL is operating since 2016. The technical systems for cooling and Ventilation CV were design, built and commissioned by the DESY work package WP34. The CV systems will be described and presented. The water cooling system consists of 3 cooling systems: 30/45 °C LCW for klystron and magnet cooling, 20/30 °C LCW for tunnel rack cooling and 8/14 °C for air conditioning and dehumidification of the air. The ventilation of the tunnels is connected to a series ventilation system from the experimental hall in direction to the injector. The series ventilation of the tunnels saves costs for air treatment with cooling, heating and dehumidification. The tunnel walls are a good heat storage that increases the air temperature stability by a factor of ten. The advantages of this concept will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-MOPO122  
About • paper received ※ 12 September 2018       paper accepted ※ 21 September 2018       issue date ※ 18 January 2019  
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TUPO027 Series Production of the Specific Waveguide Distribution for the European XFEL at DESY GUI, cavity, cryomodule, LLRF 380
 
  • B. Yildirim, S. Choroba, V.V. Katalev, P. Morozov, Y. Nachtigal
    DESY, Hamburg, Germany
  • E.M. Apostolov
    Technical University of Sofia, Sofia, Bulgaria
  
  Series Production of the Specific Waveguide Distribution for the European XFEL at DESY B.Yildirim, S.Choroba, V.Katalev, P.Morozov, Y.Nachtigal, E.Apostolov The European XFEL uses 100 accelerating cryomodules. One RF station with 10 MW klystron supplies four cryomodules, each with eight cavities, through a waveguide distribution system. The RF station operates at 1.3 GHz, 1.37 ms pulse width and 10 Hz repetition rate. The results of the cryomodule test have shown however different maximum gradients for each cavity. The maximum gradient has been measured between 11 MV/m and 31 MV/m, which requires the cavity power from 29 kW to 230 kW. To operate with the maximum energy for every cryomodule, it is necessary to supply individual power to the cavity. In this case the weakest cavity problem can be avoided. For this goal a specific waveguide distribution has been developed. 100 waveguide distributions have been successfully tailored, produced and tested at the Waveguide Assembly Test Facility (WATF) at DESY and finally assembled to the cryomodules. We present the series production of the specific waveguide distributions at the WATF.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO027  
About • paper received ※ 06 September 2018       paper accepted ※ 21 September 2018       issue date ※ 18 January 2019  
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TUPO028 Retreatment of European XFEL Series Cavities at DESY as Part of the Repair of European XFEL Accelerating Modules cavity, vacuum, SRF, linac 384
 
  • S. Sievers, N. Krupka, D. Reschke, S. Saegebarth, J. Schaffran, M. Schalwat, P. Schilling, M. Schmökel, N. Steinhau-Kühl, E. Vogel, H. Weise, B. van der Horst
    DESY, Hamburg, Germany
  • M. Wiencek
    IFJ-PAN, Kraków, Poland
  
  For the European XFEL 102 accelerating modules were built and tested. Several accelerating modules had to be reworked due to different kinds of non-conformities. The extent of this rework varied greatly. At the end of production four accelerating modules could not be qualified in time before the tunnel installation was to be finished in September 2016. Meanwhile the cavity strings of two of these accelerating modules have been disassembled in the DESY clean room. The cavities have been retreated at DESY either by additional high pressure water rinsing or BCP flash chemical treatment. All cavities were vertically tested and 15 out of 16 were qualified for the reassembly of the cavity strings. One accelerating module will be reassembled completely and tested until the end of 2018; the other will follow in the first half of 2019. We report on retreatment procedures and performance of these cavities.  
poster icon Poster TUPO028 [1.662 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO028  
About • paper received ※ 11 September 2018       paper accepted ※ 21 September 2018       issue date ※ 18 January 2019  
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TUPO029 Highlights of the XM-3 Cryomodule Tests at DESY cavity, cryomodule, operation, feedback 388
 
  • J. Branlard, V. Ayvazyan, A. Bellandi, J. Eschke, C. Gumus, D. Kostin, K.P. Przygoda, H. Schlarb, J.K. Sekutowicz
    DESY, Hamburg, Germany
  • W. Cichalewski
    TUL-DMCS, Łódź, Poland
  
  To investigate the feasibility of the continuous wave (cw) upgrade of the European XFEL (E-XFEL) DESY, on-going tests are performed on E-XFEL prototype and production cryomodules since 2011. For these studies, DESY’s Cryo-Module Test Bench (CMTB) has been equipped with a 105 kW cw operating IOT in addition to the 10MW pulsed klystron, making CMTB a very flexible test stand, enabling both cw and pulse operation. For these tests, E-XFEL-like LLRF electronics is used to stabilize amplitude and phase of the voltage Vector Sum (VS) of all 8 cavities of the cryomodule under test. The cryomodule most often tested is the pre-series XM-3, unique since it is housing one fine grain niobium and seven large grain niobium cavities. In autumn 2017, additional spacers were installed on all 8 input couplers to increase the maximum reachable loaded quality factor Ql beyond 2·107. With higher Ql, up to 6·107 for 6 cavities and 2.7·107 for 2 cavities, we have investigated the VS stability and SRF-performance of this cryomodule under various conditions of cooling down rate and operation temperature 1.65K, 1.8K and 2K, at gradients up to ca. 18MV/m. The results of these tests are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO029  
About • paper received ※ 11 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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TUPO088 Measurement of Diagnostics Response by RF Parameters for Hard X-ray Line in PAL-XFEL* diagnostics, gun, linac, timing 531
 
  • H. Yang
    PAL, Pohang, Kyungbuk, Republic of Korea
  
  Funding: *This work is supported by MSIP, Korea.
PAL-XFEL is a hard x-ray (HX) and soft x-ray (SX) FEL machine to generate 2.5 - 15 keV FEL in the HX line and 0.28 - 1.2 keV FEL in the SX line. The HX line consists of an e-gun, a laser heater, S-band accelerators, an X-band linearizer, three bunch compressors (BC), and a dog-leg line. PAL-XFEL maintains the stable operation and FEL delivery with more than 98% availability due to machine stabilities including RF modules. In order to investigate the stable operation, we measure the diagnostics response for bunch charge monitors, energy beam position monitors, bunch length monitors, and a FEL intensity with a photon beam position monitor by RF parameters - RF amplitude and phase for an e-gun, accelerators, and a linearizer. In this paper, we present mainly corresponding RF parameters for e-beam and FEL jitters by this measurement and matrix analysis. 		 
poster icon Poster TUPO088 [0.281 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO088  
About • paper received ※ 11 September 2018       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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TUPO098 Proof-of-Principle Tests for Slit-scan-based Slice Emittance Measurements at PITZ emittance, electron, laser, space-charge 553
 
  • R. Niemczyk, P. Boonpornprasert, Y. Chen, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, C. Koschitzki, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, D. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, C. Saisa-ard, F. Stephan, Q.T. Zhao
    DESY Zeuthen, Zeuthen, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  
  Transverse slice emittance is one of the most important properties of high-brightness electron beams for freeelectron lasers (FELs). The photo injector test facility at DESY in Zeuthen (PITZ) develops high-brightness electron sources for modern FELs. With a 23 MeV, 1 nC beam at PITZ the experimental slice emittance characterization with the quadrupole scan technique is complicated by strong space charge effects. Combining the slit scan technique with a transverse deflecting cavity (TDS) allows for timeresolved emittance measurements of such a space-chargedominated beam. The first proof-of-principle results of slice emittance measurements at PITZ based on the ’TDS + slit scan’-technique are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO098  
About • paper received ※ 04 September 2018       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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TUPO132 Implementation of the Beam Loading Compensation Algorithm in the LLRF System of the European XFEL LLRF, controls, cavity, FPGA 594
 
  • Ł. Butkowski, J. Branlard, M. Omet, R. Rybaniec, H. Schlarb, Ch. Schmidt
    DESY, Hamburg, Germany
  
  In the European XFEL, a maximum number of 2700 electron bunches per RF pulse with beam currents up to 4.5mA can be accelerated. Such large beam currents can cause a significant drop of the accelerating gradients, which results in large energy changes across the macro-pulse. But, the electron bunch energies should not deviate from the nominal energy to guarantee stable and reproducible generation of photon pulses for the European XFEL users. To overcome this issue, the Low Level RF system (LLRF) compensates in real-time the beam perturbation using a Beam Loading Compensation algorithm (BLC) minimizing the transient gradient variations. The algorithm takes the charge information obtained from beam diagnostic systems e.g. Beam Position Monitors (BPM) and information from the timing system. The BLC is a part of the LLRF controller implemented in the FPGA. The article presents the implementation of the algorithm in the FPGA and shows the results achieved with the BLC in the European XFEL.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TUPO132  
About • paper received ※ 11 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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WE1A04 The High Power RF System for the European XFEL klystron, cavity, GUI, gun 601
 
  • S. Choroba
    DESY, Hamburg, Germany
  
  The presentation will be on the design, construction and commissioning of the high power RF system for the European XFEL. The RF system consists of 26 high power RF stations each capable of 10MW RF pulse power. It will report on the overall system layout, cover RF system components e.g. klystrons, modulators and high power RF waveguide distribution. It will also cover system modifications during construction phase and report on commissioning results.  
slides icon Slides WE1A04 [12.620 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-WE1A04  
About • paper received ※ 17 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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WE1A05 SwissFEL Linac Commissioning Status, Current Performance and Future Plans linac, electron, experiment, operation 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       paper accepted ※ 09 October 2018       issue date ※ 18 January 2019  
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TH1A03 High Brightness Electron Beams from Plasma-based Acceleration plasma, electron, acceleration, simulation 637
 
  • A. Marocchino, A. Biagioni, E. Brentegani, E. Chiadroni, M. Ferrario, F. Filippi, A. Giribono, R. Pompili, A.R. Rossi
    INFN/LNF, Frascati (Roma), Italy
  • A. Bacci
    Istituto Nazionale di Fisica Nucleare, Milano, Italy
  • A. Cianchi
    Università di Roma II Tor Vergata, Roma, Italy
  • V. Petrillo
    Universita’ degli Studi di Milano, Milano, Italy
  
  Funding: INFN-CNAF and CINECA for high performance computing resources. European Union Horizon 2020 programme N. 53782.
Plasma Wakefield acceleration is a promising new acceleration techniques that profit by a charged bunch, e.g. an electron bunch, to break the neutrality of a plasma channel to produce a wake where a trailing bunch is eventually accelerated. The quest to achieve extreme gradient conserving high brightness has prompted to a variety of new approaches and techniques. Most of the proposed schemes are however limited to the only plasma channel, assuming in the vast majority of cases, ideal scenarios (e.g. ideal bi-gaussian bunches and uniform density plasma channels). Realistic start-to-end simulations, from the photo-cathode to FEL via a high gradient, emittance and energy spread preserving plasma section, are mandatory for paving the way towards plasma-based user facilities. 		 
slides icon Slides TH1A03 [25.814 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TH1A03  
About • paper received ※ 11 September 2018       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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TH2A01 Nitrogen Infusion R&D for CW Operation at DESY cavity, operation, SRF, niobium 652
 
  • M. Wenskat, A.D. Dangwal Pandey, B. Foster, T.F. Keller, D. Reschke, J. Schaffran, S. Sievers, N. Walker, H. Weise
    DESY, Hamburg, Germany
  • C. Bate, G.D.L. Semione, A. Stierle
    University of Hamburg, Hamburg, Germany
  • B. Foster
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  • B. Foster
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  
  The European XFEL cw upgrade requires cavities with reduced surface resistance (high Q-values) for high duty-cycle while maintaining high accelerating gradient for short-pulse operation. To improve on European XFEL performance, a recently discovered treatment is investigated: The so called Nitrogen-infusion. The recent test results of the cavity based R&D and the progress of the relevant infrastructure is presented. The aim of this approach is to establish a stable, reproducible recipe and to identify all key parameters for this process. In parallel, advanced surface analyses, such as SEM/EDX, TEM, XPS, XRR, GIXRD and TOF-SIMS, of samples after in-situ treatment, cut-outs of cavities and samples treated together with cavities are done. The aim of this approach is to understand the underlying processes of the material evolution, resulting in the improved performance. Results of these analyses, their implications for the cavity R&D, and next steps are presented.  
slides icon Slides TH2A01 [4.597 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-TH2A01  
About • paper received ※ 12 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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THPO082 Physical Design of a Rectangular RF Deflector for Ultrashort Bunch Length Measurement cavity, electron, simulation, coupling 872
 
  • J. Bai, Q.S. Chen, K. Fan
    HUST, Wuhan, People’s Republic of China
  
  Cylindrical deflectors which are now widely used for bunch length measurement suffer from the degeneration of polarization, while rectangular deflectors can separate polarization mode easily. This paper is focused on the study of a one-cell rectangular deflector, which is considerably different from cylindrical structure or multi-cell structure. A one-cell structure is free of π mode restriction and can achieve higher deflection efficiency per unit length. The proposed scheme is expected to achieve time resolution better than 200fs with the driving power less than 1MW. Cavity optimization and beam dynamic simulation are introduced in this paper.  
poster icon Poster THPO082 [0.484 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO082  
About • paper received ※ 11 September 2018       paper accepted ※ 20 September 2018       issue date ※ 18 January 2019  
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THPO091 90 kW Solid-state RF Amplifier with a TE011-mode Cavity Power-combiner at 476 MHz cavity, controls, power-supply, electron 889
 
  • Y. Otake, T. Asaka, T. Inagaki
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • S. Aizawa, K. Nagatsuka, T. Okuyama, K. Sato, H. Yamada
    Nihon Koshuha Co. Ltd, Yokohama, Japan
  
  Solid-state RF amplifiers, which have long lifetimes and small failures, are the recent trend of reliable and stable high-power rf sources for particle accelerators. Hence, we designed a 90kW solid-state amplifier with an extreme low-loss TE011 mode cavity (Q0=100, 000) power-combiner operated at 476 MHz and a 6 us pulse width. Developing this amplifier is for replacement of an IOT rf amplifier, at the X-ray free-electron laser, SACLA. In SACLA, highly RF phase and amplitude stabilities of less than 0.02 deg. and 10-4 in rms are necessary to stable lasing within a 10 % intensity fluctuation. The amplifier comprises a drive amplifier, a reentrant cavity rf power divider, 100 final amplifiers with a 1 kW output each and a TE011 mode cavity combiner. Water-cooling within 10 mK and a DC power supply with a noise of less than -100 dBV at 10 Hz for the amplifier is necessary to realize the previously mentioned stabilities. Based on the test results of the amplifier, the above-mentioned specifications with the extreme low-loss are promising. The amplifier also allows us to operate in pulsed and CW rfs for linacs and ring accelerators. We report the performance of the 90kW amplifier.  
slides icon Slides THPO091 [1.750 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO091  
About • paper received ※ 06 September 2018       paper accepted ※ 09 October 2018       issue date ※ 18 January 2019  
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THPO092 LCLSII Fundamental Power Coupler Manufacturing Status and Lesson Learned factory, operation, SRF, status 893
 
  • S. Sierra, G. Garcin, Ch.L. Lievin, G. Vignette, I. Yao Leclerc
    TED, Velizy-Villacoublay, France
  • M. Knaak, M. Pekeler
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  
  Thales and RI Research Instrument have manufactured and assembled half of the power couplers for the LCLSII project. This paper remains main characteristics of these coupler. It will also describe main challenges that were overcome among them, thickness of copper coating on Warm Internal Conductor at 150µm and lessons learned during the manufacturing phase of these couplers. The paper will also propose some possible optimization for a future mass production of such components and parameters which could be relevant for a better understanding link to the statistic results obtained.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO092  
About • paper received ※ 10 September 2018       paper accepted ※ 21 September 2018       issue date ※ 18 January 2019  
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THPO115 Consolidation and Extension of the High-gradient LINAC RF Technology at PSI linac, accelerating-gradient, cavity, polarization 937
 
  • P. Craievich, M. Bopp, H.-H. Braun, A. Citterio, H. Fitze, T. Garvey, T. Kleeb, F. Löhl, F. Marcellini, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, K. Rolli, R. Zennaro
    PSI, Villigen PSI, Switzerland
  
  For SwissFEL a novel production process for high-gradient, high-precision C-band accelerating structures had been developed at PSI and was implemented for series production in collaboration with industry. The copper parts of the structures are machined and brazed relying on a ultra-high precision manufacturing process and tight mechanical tolerances; no RF tuning methods are applied during or after production. So far none of the structures of the series production failed during RF power conditioning and operation in the SwissFEL facility. After completing the series production for SwissFEL PSI started collaborations with CERN, ELETTRA and DESY for applying the production process and related know-how to other frequencies, namely S-band (3 GHz) and X-band (12 GHz). This paper gives an overview on the ongoing and planned R\&D activities and results obtained so far.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-THPO115  
About • paper received ※ 11 September 2018       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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FR1A02 Bunch Length Measurements using Transverse Deflecting Systems diagnostics, electron, emittance, beam-diagnostic 972
 
  • M. Hüning
    DESY, Hamburg, Germany
  
  Shorter and shorter bunch lengths (some 10 fs) require sophisticated bunch length measurent devices. Free electron lasers - but not only - use transverse deflecting systems. Employing suitable diagnostic tools measurements are not limited to bunch lengths but can be extended to longitudinal profiles and phase-space distributions, and slice emittances. Not only do successfully operated systems aid the commissioning and operation of FELs but they allow control over more sophisticated phase-space manipulations. The design and construction of such systems, actually operated at different RF frequencies, includes cavity design and fabrication, powerful RF systems, low level RF control, beam lines, diagnostics, and data analysis.  
slides icon Slides FR1A02 [6.054 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-FR1A02  
About • paper received ※ 11 September 2018       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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FR1A06 Pulse-by-Pulse Beam Parameter Switching of High-Quality Beams for Multi-Beamline Operation at SACLA electron, controls, laser, optics 988
 
  • H. Maesaka, T. Fukui, T. Hara, Y. Otake
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • T. Hasegawa, O. Morimoto, Y. Tajiri, S. Tanaka, M. Yoshioka
    SES, Hyogo-pref., Japan
  • N. Hosoda, S. Matsubara, T. Ohshima
    JASRI/SPring-8, Hyogo-ken, Japan
  • C. Kondo, M. Yamaga
    JASRI, Hyogo, Japan
  
  The main linac of the X-ray free electron laser (XFEL), SACLA, provides electron beams to two XFEL beamlines and a beam transport line to the SPring-8 storage ring. In order to utilize these beamlines at the same time, a kicker magnet was installed into the switch yard and electron beams with a 60 Hz repetition rate can be distributed to these beamlines pulse-by-pulse. Since a beam energy and an optimum bunch length are usually different for each beamline, the operation condition of each acceleration unit, such as the rf phase, the trigger permission, etc., has to be changed pulse-by-pulse. Even in that case, the electron beam quality, such as 1 mm mrad normalized emittance, 10 fs bunch length, 10 kA peak current, etc., must not be deteriorated. At first, we developed a parameter control software that was able to manage two XFEL beamlines with an equal repetition rate. Different energy beams with sufficient quality for lasing were successfully distributed to the two XFEL beamlines and the XFEL performances of both beamlines were optimized simultaneously. The development status of a new parameter switching system with an arbitrary sequence of the destinations will also be reported.  
slides icon Slides FR1A06 [6.179 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2018-FR1A06  
About • paper received ※ 16 September 2018       paper accepted ※ 19 September 2018       issue date ※ 18 January 2019  
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FR2A02 Commissioning of the European XFEL MMI, operation, photon, linac 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       paper accepted ※ 17 October 2018       issue date ※ 18 January 2019  
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