Energy spread analysis for a multiharmonic optical klystron (MHOK)

Summary form only given. Optical klystrons (OKs) based on two wiggler sections of the same periodicity and a dispersion section in between have been used to enhance the interaction gain in free electron lasers (FELs), especially those used in storage rings. It has been shown recently that if the first wiggler section is replaced by a wiggler of multiple periodicities, a multiharmonic wiggler, more electrons in the beam will be grouped into tight bunches and as a result the small signal gain of the resultant device will be enhanced considerably. Such an arrangement is known as a multiharmonic optical klystron (MHOK). To assess their practical application, it is important to establish whether multiharmonic optical klystrons requires a significantly better beam quality than conventional OKs. In this contribution, an energy spread analysis is presented for MHOKs in the small signal limit.