A model of laser heater undulator system for self-amplified free electron lasers

摘要

The laser heater has been proposed to damp the microbunching instability affecting the operation of free electron laser (FEL) self-amplified spontaneous emission (SASE) devices. The heater may be provided by an external laser or by a FEL oscillator using the same electron beam driving the SASE-FEL operation. The second solution offers undoubtful advantages, which will be discussed in this paper. We present simple physical arguments which allow the derivation of a criterion yielding the amount of laser power necessary to damp the instability, without compromising the FEL SASE operation.