AN R&D PROGRAM FOR A HIGH BRIGHTNESS ELECTRON BEAM SOURCE AT LNF

The design of a high gradient S-band Photo-Injector system for the production and study of high brightness electron beams is in progress at the Frascati Laboratory, in the frame of a collaboration among INFN, ENEA, CNR, Univ. Roma TV, INFM and ST. This collaboration submitted last year a proposal to a dedicated call for proposals launched by our government, meant to be the first step of a R&D program strategically oriented to a large X-ray FEL initiative. This proposal was approved (December 2001), among others, for a total allocated budget of 9.5 M€ .The construction of the system is expected to start soon: it is comprised of a RF gun driven by a Ti:Sa laser to produce 10 ps flat-top pulses on the photocathode (up to a few nC bunch charge), injecting into two SLAC structures which boost the beam up to 150 MeV. We foresee to conduct investigations on the emittance correction technique and on the RF compression (velocity bunching) scheme, which is expected to increase the natural peak current (100 A) achievable at the gun exit up to a few kA level, with proper preservation of the transverse emittance. Although the system is expected to drive a FEL experiment in the UV region, it will be used also to investigate beam physics issues like surface roughness induced wake-fields, bunch length measurements in the sub-ps range, emittance degradation in magnetic compressors due to CSR and an eventual experiment of Compton backscattering to produce sub-ps X-ray pulses.