UW-Madison/SRC, Madison, Wisconsin
SLAC, Menlo Park, California
Bunch compression for a free-electron laser (FEL) may cause growth of current and energy fluctuations at wavelengths shorter than the bunch length. This microbunching instability may disrupt FEL performance or it may be used to produce coherent radiation. We give analytic formulas that approximate microbunching growth and apply them to the Wisconsin FEL (WiFEL).
DESY, Hamburg
Longitudinal space charge (LSC) driven microbunching instability in electron beam formation systems of X-ray FELs is a recently discovered effect hampering beam instrumentation and FEL operation. The instability was observed in different facilities in infrared and visible wavelength ranges. In this paper we propose to use such an instability for generation of VUV and X-ray radiation. A typical longitudinal space charge amplifier (LSCA) consists of few amplification cascades (drift space plus chicane) with a short undulator behind the last cascade. A wavelength compression could be an attractive option for LSCA since the process is broadband, and a high compression stability is not required. LSCA can be used as a cheap addition to the existing or planned short-wavelength FELs. In particular, it can produce the second color for a pump-probe experiment. It is also possible to generate attosecond pulses in the VUV and X-ray regimes. Finally, since the amplification mechanism is broadband and robust, LSCA can be an interesting alternative to self-amplified spontaneous emission free electron laser (SASE FEL) in the case of using laser-plasma accelerators as drivers of light sources.
Report DESY 10-048, March 2010
