PHASE STABILITY OF THE NEXT GENERATION RF FIELD CONTROL FOR VUV- AND X-RAY FREE ELECTRON LASER

For pump-probe experiments at FLASH and XFELs (free-electron lasers) the stability of the electron beam arrival time with respect to the timing reference depends critically on the phase and amplitude stability of the injector. An arrival time jitter below the longitudinal bunch duration of 60fs (rms) requires 0.01 ◦ (rms) phase and 0.01% (rms) amplitude stability. The cavity field detection critically influences the regulation of the acceleration field. In this paper we present the phase noise budget for a RFregulation system including the noise characterization of its subcomponents, in particular downconverter,analog-todigital converter, vector-modulator, master oscillator and klystron. We investigate the cavity field jitter induced by these noise sources within the regulation and determine the optimal controller gain.