Microbunching Instability due to Bunch Compression
Magnetic bunch compressors are designed to increase the peak current while maintaining the transverse and longitudinal emittances in order to drive a short-wavelength free electron laser (FEL). Recently, several linac-based FEL experiments observe self-developing micro-structures in the longitudinal phase space of electron bunches undergoing strong compression [1-3]. In the mean time, computer simulations of coherent synchrotron radiation (CSR) effects in bunch compressors illustrate that a CSR-driven microbunching instability may significantly amplify small longitudinal density and energy modulations and hence degrade the beam quality [4]. Various theoretical models have since been developed to describe this instability [5-8]. It is also pointed out that the microbunching instability may be driven strongly by the longitudinal space charge (LSC) field [9,10] and by the linac wakefield [11] in the accelerator, leading to a very large overall gain of a two-stage compression system such as found in the Linac Coherent Light Source (LCLS) [12]. This paper reviews theory and simulations of microbunching instability due to bunch compression, the proposed method to suppress its effects for short-wavelength FELs, and experimental characterizations of beam modulations in linear accelerators. A related topic of interests is microbunching instability in storage rings, which has been reported in the previous ICFA beam dynamics newsletter No. 35 (http://wwwbd. fnal.gov/icfabd/Newsletter35.pdf).
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 877512
- Report Number(s):
- SLAC-PUB-11597; TRN: US0601457
- Journal Information:
- ICFA Beam Dynamics Newsletter, Vol. 38
- Country of Publication:
- United States
- Language:
- English
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