TUCOWBS —  WG2: ERL beam dynamics and instrumentation   (17-Sep-19   09:00—10:30)
Chair: S.A. Bogacz, JLab, Newport News, Virginia, USA
Paper Title Page
TUCOWBS01
Longitudinal Phase Space Dynamics in ERLs  
 
  • S.V. Benson, C. Tennant
    JLab, Newport News, Virginia, USA
  • D. Douglas
    Douglas Consulting, York, Virginia, USA
  • P.E. Evtushenko
    HZDR, Dresden, Germany
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Both the dynamics and the architecture of an energy recovery linac are primarily determined by the longitudinal match. This match can be manipulated by both the magnetic lattice and the RF systems. Here we will present a few examples of systems and the longitudinal solutions found for each. The first application is a free-electron laser application where a short bunch and high peak current are required. The laser increases the energy spread and lowers the energy and this must be compensated in the ERL design. The second application is for an internal target experiment where the need was for small energy spread rather than a short bunch. The third example is for an electron cooler where the bunch must be very long with extremely small energy spread. The beam disruption due to cooling is small but CSR and microbunching effects are a real challenge. In the FEL, the longitudinal matching is mainly accomplished via lattice matching while in the cooler application the RF system is the dominant method to control the phase space. The internal target can be addressed either way.
 
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TUCOWBS02
Beyond the Limits of 1D Coherent Synchrotron Radiation  
 
  • P.H. Williams
    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. 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 TUCOWBS02 [1.146 MB]  
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TUCOWBS03
CSR Phase Space Dilution in CBETA  
 
  • W. Lou, G.H. Hoffstaetter, D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • C.E. Mayes
    SLAC, Menlo Park, California, USA
 
  While Energy Recovery Linac (ERLs) give promise to deliver unprecedentedly high beam current with simultaneously small emittance, Coherent Synchrotron Radiation (CSR) can pose detrimental effect on the beam at high bunch charges and short bunch lengths. CBETA, the Cornell BNL ERL Test Accelerator, will be the first multi-turn ERL with SRF accelerating cavities and Fixed Field Alternating gradient (FFA) beamline. To investigate the CSR effects on CBETA, the established simulation code Bmad has been used to track a bunch with different CSR parameters. We found that CSR causes phase space dilution, and the effect becomes more significant as the bunch charge and recirculation pass increase. Convergence tests have been performed for the CSR parameters to validate the observed micro-bunching instability. Potential ways to mitigate the effect involving vacuum chamber shielding and increasing bunch length are also being investigated.  
slides icon Slides TUCOWBS03 [5.215 MB]  
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