Author: Li, R.
Paper Title Page
MOP052 Linear Vlasov Solver For Microbunching Gain Estimation with Inclusion of CSR, LSC, And Linac Geometric Impedances 147
 
  • C.-Y. Tsai
    Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
  • D. Douglas, R. Li, C. Tennant
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
As is known, microbunching instability (MBI) has been one of the most challenging issues in designs of magnetic chicanes for short-wavelength free-electron lasers or linear colliders, as well as those of transport lines for recirculating or energy recovery linac machines. To more accurately quantify MBI in a single-pass system, we further extend and continue to increase the capabilities of our previously developed linear Vlasov solver [1] to incorporate more relevant impedance models into the code, including transient and steady-state free-space and/or shielding CSR impedances, the LSC and linac geometric impedances with extension of the existing formulation to include beam acceleration [2]. Then, we directly solve the linearized Vlasov equation numerically for microbunching gain amplification factor. In this study we apply this code to a beamline lattice of transport arc [3] following an upstream linac section. The resultant gain functions and spectra are presented here, and some results are compared with particle tracking simulation by ELEGANT [4]. We also discuss some underlying physics with inclusion of these collective effects and the limitation of the existing formulation. It is anticipated that this more thorough analysis can further improve the understanding of MBI mechanisms and shed light on how to suppress or compensate MBI effects in lattice designs.
[1] C. -Y. Tsai et al., FEL'14 (THP022), IPAC'15 (MOPMA028) and ERL2015 (TUICLH2034)
[2] M. Venturini, Phys. Rev. ST Accel. Beams 10, 104401 (2007)
[3] D. Douglas et al., arXiv: 1403.2318v1 [physics.acc-ph]
[4] M. Borland, APS Light Source Note LS-287 (2000)
 
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MOP087 Multistage CSR Microbunching Gain Development in Transport or Recirculation Arcs 263
 
  • C.-Y. Tsai
    Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
  • D. Douglas, R. Li, C. Tennant
    JLab, Newport News, Virginia, USA
 
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Coherent synchrotron radiation (CSR) induced microbunching instability has been one of the most challenging issues in the design of modern accelerators. A linear Vlasov solver has been developed [1] and applied to investigate the physical processes of microbunching gain amplification for several example lattices [2]. In this paper, by further extending the concept of stage gain as proposed by Huang and Kim [3], we develop a method to characterize the microbunching development in terms of stage orders that allow the quantitative comparison of optics impacts on microbunching gain for different lattices. We find that the microbunching instability in our demonstrated arcs has a distinguishing feature of multistage amplification (e.g, up to 6th stage amplification for our example transport arcs, in contrast to two-stage amplification for a typical 4-dipole bunch compressor chicane). We also try to connect lattice optics pattern with the obtained stage gain functions by a physical interpretation. This Vlasov analysis is validated by ELEGANT [4] tracking results with excellent agreement.
[1] C. -Y. Tsai et al., MOP052, these proceedings
[2] See, for example, C. -Y. Tsai et al., ERL2015 (TUICLH2034)
[3] Z. Huang and K. -J. Kim, Phys. Rev. ST Accel. Beams 5, 074401 (2002)
[4] M. Borland, APS Light Source Note LS-287 (2000)
 
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