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[Andreas Adelmann <andreas.adelmann AT psi.ch>]

Review of Microbunching Beam Instability in the XFEL Driving Linacs - Part 2

Yujong Kim

Recently, many laboratories in the world have been competing to build next generation light source facilities to supply coherent,
ultra-bright, and ultra-short X-rays. With the advanced X-ray photon beams, beamline users can perform various status-of-art
scientific experiments with femtosecond temporal resolution and atomic-scale spatial resolution. Up to now, linear accelerator
(linac) based X-ray Free Electron Laser (XFEL) has been considered as the best candidate to supply such an advanced photon beams at
the hard X-ray region. The XFEL facility generally consists of a low emittance electron gun, a high energy linac, and a long undulator.
To get the power saturation of XFEL photon beams in the long undulator easily, lower slice emittance and lower slice energy spread are required,
while a higher peak current is needed. However, those slice beam parameters can be diluted, and the FEL lasing mechanism can be destroyed due
to a fatal microbunching beam instability in the FEL driving linac. The instability is generated if electron beams has a small density or
energy modulation in beam profiles. During this talk, speaker will introduce basic concepts and simulation results on the microbunching
instability due to collective self-fields such as longitudinal space charge, coherent synchrotron radiation, geometrical short-range wakefields.
Additionally, he will review a new type microbunching instability or Coherent Optical Transition Radiation (COTR) initiated by the shot
noise and its possibility in the PSI-XFEL driving linac.



Today: WBGB 21, 14.00

See you Andreas

-- 
Dr. sc. math. Andreas (Andy) Adelmann
Staff Scientist
Paul Scherrer Institut WLGB/132 CH-5232 Villigen PSI
Phone Office: xx41 56 310 42 33 Fax: xx41 56 310 31 91
Phone Home: xx41 62 891 91 44
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Wednesday: ETH CAB F 10.1  xx41 44 632 82 76
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The more exotic, the more abstract the knowledge, 
the more profound will be its consequences."
Leon Lederman 
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