Physical design of a wavelength tunable fully coherent VUV source using a self-seeding free electron laser

摘要

In order to meet requirements of the synchrotron radiation users, a fullycoherent VUV free electron laser (FEL) has been preliminarily designed. Oneimportant goal of this design is that the radiation wavelength can be easilytuned in a broad range (70-170 nm). In the light of the users' demand and ouractual conditions, the self-seeding scheme is adopted for this proposal.Firstly, we attempt fixing the electron energy and only changing the undulatorgap to varying the radiation wavelength, but the analysis implies that it isdifficult because of the great difference of the power gain length and FELefficiency at different wavelength. Therefore, dividing the wavelength rangeinto three subareas is considered. In each subarea, a constant electron energyis used and the wavelength tuning is realized only by adjusting the undulatorgap. The simulation results shows that this scheme has an acceptableperformance.