Electron Accelerators and Applications
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MOPOPA02 Identification of the Mechanical Dynamics of the Superconducting Radio-Frequency Cavities for the European XFEL CW Upgrade 76
  • W.H. Syed, A. Bellandi, J. Branlard, A. Eichler
    DESY, Hamburg, Germany
  The European X-Ray Free-Electron Laser (EuXFEL) is to-date the largest X-ray research facility around the world which spans over 3.4 km. EuXFEL is currently being operated in a pulsed mode with a repetition rate of 10Hz. One upgrade scenario consists of operating the EuXFEL also in a Continuous-Wave (CW) mode of operation to improve the quality of experiments. This upgrade brings new challenges and requires new algorithms to deal with controlling a stable accelerating field inside the Superconducting Radiofrequency (SRF) accelerating cavities and keeping them on resonance in this new mode of operation. The purpose of this research work is to identify the mechanical dynamics of the cavities which will facilitate the development of the resonance controller for the CW upgrade. To this extent, experiments were conducted at a test bench. For the first time, in this work, two different types of spectrally rich excitation signals: multi-sine and stepped-sine are used to excite the mechanical dynamics of the cavities using the piezo actuator. After the analysis of experimental data, mechanical modes are successfully identified and will be used to design the controller.  
poster icon Poster MOPOPA02 [0.687 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-MOPOPA02  
About • Received ※ 23 August 2022 — Revised ※ 25 August 2022 — Accepted ※ 26 August 2022 — Issue date ※ 01 September 2022
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MOPOPA03 Beam-Transient-Based LLRF Voltage Signal Calibration for the European XFEL 80
  • N. Walker, V. Ayvazyan, J. Branlard, S. Pfeiffer, Ch. Schmidt
    DESY, Hamburg, Germany
  The European XFEL linac consists of 25 superconducting RF (SRF) stations. With the exception of the first station which is part of the injector, each station comprises 32 1.3-GHz SRF TESLA cavities, driven by a single 10-MW klystron. A sophisticated state-of-the-art low-level RF (LLRF) system maintains the complex vector sum of each RF station. Monitoring and maintaining the calibration of the cavity electric field (gradient) probe signals has proven critical in achieving the maximum energy performance and availability of the SRF linac. Since there are no dedicated diagnostics for cross-checking calibration of the LLRF system, a procedure has been implemented based on simultaneously measuring the beam transient in open-loop operation of all cavities. Based on methods originally developed at FLASH, the European XFEL procedure makes use of automation and the XFEL LLRF DAQ system to provide a robust and relatively fast (minutes) way of extracting the transient data, and is now routinely scheduled once per week. In this paper, we will report on the background, implementation, analysis methods, typical results, and their subsequent application for machine operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-MOPOPA03  
About • Received ※ 13 August 2022 — Revised ※ 23 August 2022 — Accepted ※ 14 September 2022 — Issue date ※ 27 September 2022
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MOPOPA04 Simulation Study of an Accelerator-based THz FEL for Pump-Probe Experiments at the European XFEL 83
  • P. Boonpornprasert, G.Z. Georgiev, M. Krasilnikov, X.-K. Li, A. Lueangaramwong
    DESY Zeuthen, Zeuthen, Germany
  The European XFEL considers to perform THz-pump and X-ray-probe experiments. A promising concept to provide the THz pulses with satisfactory properties for the experiments is to generate them using a linear accelerator-based free-electron laser (FEL). A simulation study of a THz FEL facility capable of generating powerful tunable coherent THz radiation that covers the wavelength range of 25 ’m to 100 ’m was performed. An accelerator beamline layout based on the Photo Injector Test Facility at DESY in Zeuthen (PITZ) and an APPLE-II undulator with a period length of 40 mm were used in the simulation study. Results of the study are presented and discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-MOPOPA04  
About • Received ※ 25 August 2022 — Revised ※ 27 August 2022 — Accepted ※ 30 August 2022 — Issue date ※ 05 September 2022
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MOPOPA11 Laser-to-RF Synchronisation Drift Compensation for the CLARA test facility 87
  • J. Henderson, A.J. Moss, E.W. Snedden
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • A.C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  Femtosecond synchronisation between charged particle beams and external laser systems is a significant challenge for modern particle accelerators. To achieve femtosecond synchronisation of the CLARA electron beam and end user laser systems will require tight synchronisation of several accelerator subsystems. This paper reports on a method to compensate for environmentally driven long-term drift in Laser-RF phase detection systems.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-MOPOPA11  
About • Received ※ 22 August 2022 — Revised ※ 26 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 15 September 2022
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MOPOPA12 Preserving Bright Electron Beams: Distorted CSR Kicks 91
SUPCRI08   use link to see paper's listing under its alternate paper code  
  • A. Dixon, T.K. Charles
    The University of Liverpool, Liverpool, United Kingdom
  • T.K. Charles, P.H. Williams
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • S. Thorin
    MAX IV Laboratory, Lund University, Lund, Sweden
  • P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  Short pulse, low emittance electron beams are necessary to drive bright FEL X-rays, for this reason it is important to preserve and limit emittance growth. The strong bunch compression required to achieve the short bunches, can lead to coherent synchrotron radiation (CSR)-induced emittance growth, and while there are some methods of CSR cancel- lation, these methods may be less effective when the CSR kicks are distorted. In an attempt to understand why CSR kicks become distorted, we compare the CSR kicks calcu- lated using the whole beam parameters to the CSR kicks calculated using the longitudinally sliced beam parameters, when propagated to the end of the bunch compressor. We find that CSR kicks can become distorted when calculated with non-uniform slice beam parameters. While slice beam parameters that are uniform along the centre of the bunch, do not result in distorted CSR kicks.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-MOPOPA12  
About • Received ※ 24 August 2022 — Revised ※ 26 August 2022 — Accepted ※ 27 August 2022 — Issue date ※ 31 August 2022
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MOPOPA13 200 MV Record Voltage of vCM and LCLS-II-HE Cryomodules Production Start Fermilab 95
  • T.T. Arkan, D. Bafia, D.J. Bice, J.N. Blowers, A.T. Cravatta, B. Giaccone, C.J. Grimm, B.D. Hartsell, J.A. Kaluzny, M. Martinello, T.H. Nicol, Y.M. Orlov, S. Posen
    Fermilab, Batavia, Illinois, USA
  • M. Checchin
    SLAC, Menlo Park, California, USA
  Funding: Department of Energy
The Linac Coherent Light Source (LCLS) is an X-ray science facility at SLAC National Accelerator Laboratory. The LCLS-II project (an upgrade to LCLS) is in the commissioning phase; the LCLS-II-HE (High Energy) project is another upgrade to the facility, enabling higher energy operation. An electron beam is accelerated using superconducting radio frequency (SRF) cavities built into cryomodules. It is planned to build 24 1.3 GHz standard cryomodules and 1 1.3 GHz single-cavity Buncher Capture Cavity (BCC) cryomodule for the LCLS-II-HE project. Fourteen of these standard cryomodules and one BCC are planned to be assembled and tested at Fermilab. Procurements for standard cryomodule components are nearing completion. The first LCLS-II-HE cryomodule, referred to as the verification cryomodule (vCM) was assembled and tested at Fermilab. Fermilab has completed the assembly of the second cryomodule. This paper presents LCLS-II-HE cryomodule production status at Fermilab, emphasizing the changes done based on the successes, challenges, mitigations, and lessons learned from LCLS-II; validation of the changes with the excellent vCM results.
poster icon Poster MOPOPA13 [1.975 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-MOPOPA13  
About • Received ※ 10 August 2022 — Revised ※ 26 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 09 September 2022
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Progress of Shanghai HIgh repetitioN rate XFEL and Extreme light facility (SHINE)  
  • B. Liu, D. Wang, L. Yin
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • Z.T. Zhao
    SSRF, Shanghai, People’s Republic of China
  The first hard X-ray FEL light source in China, the so-called Shanghai HIgh repetitioN rate XFEL and Extreme light facility (SHINE), is under construction. It includes an 8 GeV superconducting linac and will be built up in 2025. The first CM has been tested and the commissioning of the injector will start in 2023. Progress of the SHINE project will be presented.  
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WE2AA01 The CompactLight Design Study 642
  • A. Latina
    CERN, Meyrin, Switzerland
  • G. D’Auria, R.A. Rochow
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  CompactLight (XLS) is an H2020 Design Study funded by the European Union under grant agreement No. 777431 and carried out by an international collaboration of 23 international laboratories and academic institutions, three private companies, and five third parties. The project, which started in January 2018 with a duration of 48 months, aimed to design an innovative, compact, and cost-effective hard X-ray FEL facility complemented by a soft X-ray source. In December 2021, the Conceptual Design Report was completed. The result is an accelerator that can be operated at up to 1 kHz pulse repetition rate, beyond today’s state of the art, using the latest concepts for high brightness electron photoinjectors, very high gradient accelerating structures in X-band, and novel short-period undulators. This paper gives an overview of the current status, focusing particularly on the technological challenges addressed and their future applications to compact accelerator-based facilities.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-WE2AA01  
About • Received ※ 19 August 2022 — Revised ※ 25 August 2022 — Accepted ※ 30 August 2022 — Issue date ※ 02 September 2022
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High Extraction Efficiency Operation of Oscillator-Type Free Electron Laser Driven by a Normal Conducting Linac  
  • H. Zen
    Kyoto University, Kyoto, Japan
  Funding: MEXT Quantum Leap Flagship Program (MEXT Q-LEAP) Grant Number JPMXS0118070271.
The highest extraction efficiency (9.4%) of a Free Electron Laser (FEL) oscillator has been achieved at the mid-infrared FEL facility of Kyoto University*. The FEL is driven by a normal conducting linac consisting of a thermionic/photocathode RF gun and a traveling wave accelerator tube. The dynamic cavity desynchronization method**,*** was used to achieve the high extraction efficiency with a short macro-pulse duration (7 micro-s). Because of the interaction between the electron beam and FEL electromagnetic field, a maximum electron energy decrease of 16% was observed. An FEL micro-pulse energy of ~100 micro-J with the micro-pulse duration of 150 fs at the wavelength of 11 micro-m was observed. The detailed structure of the FEL micro-pulse was measured using a fringe resolved autocorrelation with a phase retrieval algorithm. As a result, superradiance ringing (or Burnham Chiao ringing), i.e. generation of multiple sub-pulses and 180-degree phase jumps between those sub-pulses, was experimentally observed for the first time in an FEL oscillator.
*H. Zen et al., Applied Physics Express 13, 102007 (2020)
**R.J. Bakker et al., Physical Review E 48, R3256 (1993)
***H. Zen et al., Physical Review Accelerators and Beams 23, 070701 (2020)
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TH2AA02 RF System Performance in the SwissFEL Linac 679
  • C.D. Beard, J. Alex, H.-H. Braun, P. Craievich, Z. Geng, N. Hiller, R. Kalt, C. Kittel, T. Lippuner, T.G. Lucas, M. Pedrozzi, E. Prat, S. Reiche, T. Schietinger, W.T. Tron, D. Voulot, R. Zennaro
    PSI, Villigen PSI, Switzerland
  The Hard X-ray FEL machine SwissFEL at the Paul Scherrer Institut in Switzerland is commissioned and transiting to user operation smoothly. FEL operation requires stringent requirements for the beam stability at the linac output, such as the electron bunch arrival time, peak current and beam energy. Among other things, a highly stable RF system is required to guarantee the beam stability. RF performance often dominates the overall performance and availability of FELs, and for this reason the SwissFEL RF system has been designed based on the state-of-the-art technologies that have enabled excellent RF stability, resulting in an arrival time jitter of ~10 fs rms and relative beam energy stability of 10-4 rms. This paper aims to provide an understanding of the peak performance of the RF systems and to highlight possible limitation currently faced, focusing on the S-, C- and X-Band systems.  
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-TH2AA02  
About • Received ※ 20 August 2022 — Revised ※ 26 August 2022 — Accepted ※ 30 August 2022 — Issue date ※ 02 September 2022
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