THB —  Thursday - Late Morning   (29-Aug-19   11:15—12:45)
Chair: S. Bettoni, CERN, Meyrin, Switzerland
Paper Title Page
THB01
Using an E-SASE Compression to Suppress Microbunch Instability and Resistive-Wall Wake Effects  
 
  • P.M. Anisimov
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Research presented in this presentation was supported by the Laboratory Directed Research and Development program of Los Alamos National Laboratory under project number 20180535ECR.
High brightness electron sources, such as photo injectors, deliver electron beams with a few Ampere peak currents yet high energy X-ray free-electron lasers require electron beams with >3kA peak currents to operate. In order to bridge this gap, a 100x beam compression that does not reduce the brightness of an electron beam has to take place. We will present our study of an E-SASE based compression scheme aimed at satisfying the requirements of high energy X-ray free electron lasers regarding electron beam currents, energy spreads and emittances. The E-SASE compression is based on a laser modulation of an electron beam energy and subsequent compression in a small magnetic chicane, which results in a train of high current bunches that are synchronized to the external laser and could be used in pump-probe experiments. A unique time profile of an electron beam is expected to suppress the resistive-wall wake effects.
 
slides icon Slides THB01 [11.055 MB]  
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THB02 Understanding 1D to 3D Coherent Synchrotron Radiation Effects 578
 
  • A.D. Brynes
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Collective effects such as coherent synchrotron radiation (CSR) can have a strong influence of the properties of an electron bunch with respect to the quality of the FEL light that it produces. In particular, CSR experienced by a bunch on a curved trajectory can increase the transverse emittance of a beam. In this contribution, we present an extension to the well-established 1D theory of CSR by accounting fully for the forces experienced in the entrance and exit transients of a bending magnet. A new module of the General Particle Tracer (GPT) tracking code was developed for this study, showing good agreement with theory. In addition to this analysis, we present experimental measurements of the emittance growth experienced in the FERMI bunch compressor chicane as a function of bunch length. When the bunch undergoes extreme compression, the 1D theory breaks down and is no longer valid. A comparison between the 1D theory, experimental measurements and a number of codes which simulate CSR differently are presented, showing better agreement when the transverse properties of the bunch are taken into account.  
slides icon Slides THB02 [3.591 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THB02  
About • paper received ※ 19 August 2019       paper accepted ※ 27 August 2019       issue date ※ 05 November 2019  
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THB03
Emittance Measurements and Minimization at SwissFEL  
 
  • E. Prat, M. Aiba, S. Bettoni, P. Craievich, P. Dijkstalpresenter, E. Ferrari, R. Ischebeck, F. Löhl, A. Malyzhenkov, G.L. Orlandi, S. Reiche, T. Schietinger
    PSI, Villigen PSI, Switzerland
 
  The transverse emittance of the electron beam is a fundamental parameter that determines the performance of free-electron-lasers (FELs). In this contribution, we present emittance measurements carried out at SwissFEL, the X-ray FEL facility that recently started to operate at PSI in Switzerland, including a description of our measurement methods and optimization procedures. We obtained slice emittance values at the undulator entrance down to ~200 nm for an electron beam with a charge of 200 pC and an r.m.s. duration of ~30 fs. Furthermore, we achieved slice emittances as low as ~100 nm for 10 pC beams with few femtosecond duration.  
slides icon Slides THB03 [6.285 MB]  
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THB04 Longitudinal Phase Space Study on Injector Beam of High Repetition Rate X-Ray FEL 584
 
  • Q. Gu
    SSRF, Shanghai, People’s Republic of China
  • Z. Wang
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
 
  The longitudinal phase space of the high repetition rate injector beam usually twisted and deteriorated by the space charge force. It causes the correlated energy spread and the local chirp within the beam, which could not compensated by the harmonic correction. As a consequence of this problem, one could not get ideal beam with a peak current more than kiloamperes. In this paper several approaches have been studied to relieve this effect and get the well compressed beam for the lasing.  
slides icon Slides THB04 [3.151 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THB04  
About • paper received ※ 26 August 2019       paper accepted ※ 16 September 2019       issue date ※ 05 November 2019  
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