Author: Emma, P.
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MOP056 Reversible Electron Beam Heater without Transverse Deflecting Cavities 166
 
  • G. Stupakov, P. Emma
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by Department of Energy contract DE-AC03-76SF00515.
Suppression of microbunching instability in modern FELs is an important issue that often limits the performance of the machine. A technique to suppress the instability with the help of a reversible electron beam heater was proposed by C. Behrens, Z. Huang, and D. Xiang [*]. It employs transverse deflecting cavities synchronized in a way that one of the cavities, located before a bunch compressor, generates a slice energy spread, while the other one removes it after the beam passes through the bunch compressor. Being an attractive approach, this concept unfortunately imposes extremely tight tolerances on the synchronization of the cavities. In this paper we demonstrate that a reversible heater equivalent to that of Behrens et al. can be designed using much simpler elements: bend magnets and quadrupoles in combination with the energy chirp of the beam.
* C. Behrens, Z. Huang, and D. Xiang, PRST-AB 15, 022802 (2012).
 
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TUP007 High Fidelity Start-to-end Numerical Particle Simulations and Performance Studies for LCLS-II 342
 
  • G. Marcus, Y. Ding, P. Emma, Z. Huang, T.O. Raubenheimer, L. Wang
    SLAC, Menlo Park, California, USA
  • J. Qiang, M. Venturini
    LBNL, Berkeley, California, USA
 
  High fidelity numerical particle simulations that leverage a number of accelerator and FEL codes have been used to analyze the LCLS-II FEL performance. Together, the physics models that are included in these codes have been crucial in identifying, understanding, and mitigating a number of potential hazards that can adversely affect the FEL performance, some of which are discussed in papers submitted to this conference[*, **]. Here, we present a broad overview of the LCLS-II FEL performance, based on these start-to-end simulations, for both the soft X-ray and hard X-ray undulators including both SASE and self-seeded operational modes.
* M. Venturini, et al., The microbunching instability and LCLS-II lattice design: lessons learned, FEL'15
** Z. Zhang, et al., Microbunching-induced sidebands in a seeded free-electron laser, FEL'15
 
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TUP066 Benchmark of ELEGANT and IMPACT 505
 
  • L. Wang, P. Emma, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
  • J. Qiang
    LBNL, Berkeley, California, USA
 
  The beam dynamics codes ELEGANT and IMAPCT have many users. We use these two codes for the design of LCLSII. Both codes use a 1D model for the coherent synchrotron radiation (CSR) in bend magnets. In addition, IMPACT has a 3D space-charge model, while ELEGANT uses a 1D model. To compare the two codes, especially the space-charge effects, we systematically benchmark the two codes with different physics aspects: wakefields, CSR and space-charge forces.  
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WEP025 Effect of Microbunching on Seeding Schemes for LCLS-II 639
 
  • G. Penn, J. Qiang
    LBNL, Berkeley, California, USA
  • P. Emma, E. Hemsing, Z. Huang, G. Marcus, T.O. Raubenheimer, L. Wang
    SLAC, Menlo Park, California, USA
 
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
External seeding and self-seeding schemes are particularly sensitive to distortions and fluctuations in the electron beam profile. Wakefields and the microbunching instability are important sources of such imperfections. Even at modest levels, their influence can degrade the spectrum and decrease the output brightness. These effects are evaluated for seeded FELs at the soft X-ray beam line of LCLS-II. FEL simulations are performed in GENESIS based on various realistic electron distributions obtained using the IMPACT tracking code. The sensitivity depends on both the seeding scheme and the output wavelength.
 
poster icon Poster WEP025 [0.962 MB]  
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WEP070 Start-to-End Simulation of the LCLS-II Beam Delivery System with Real Number of Electrons 714
 
  • J. Qiang, C.E. Mitchell, C. F. Papadopoulos, M. Venturini
    LBNL, Berkeley, California, USA
  • Y. Ding, P. Emma, Z. Huang, G. Marcus, Y. Nosochkov, T.O. Raubenheimer, L. Wang, M. Woodley
    SLAC, Menlo Park, California, USA
 
  The LCLS-II as a next generation high repetition rate FEL based X-ray light source will enable significant scientific discoveries. In this paper, we report on the progress in the design of the accelerator beam delivery system through start-to-end simulations. We will present simulation results for three cases, 20 pC, 100 pC and 300 pC that are transported through the hard X-ray line and the soft X-ray line for FEL radiation.  
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