Bd-palaver mailing list

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

Dear colleagues please note we have a BD-Palaver on November 18 at WBGB 19 (14.00).

Review of Microbunching Beam Instability in the XFEL Driving Linacs

by 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.



Hope to see you all

with the best regards

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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