New Optimization for the Lcls Photo-injector

A new parameter optimization of the LCLS photo-injector beamline minimizing the transverse emittance has been established for operating the gun at 120MV/m. The design goals of the LCLS photo-injector beamline are to provide a 150 MeV, 10ps FWHM, 1nC bunch at 120Hz with less than 1.2 mm.mrad for the projected emittance and less than 1 mm.mrad for the slice emittance for 80 slices out of 100. The new optimization gives 0.92 mm.mrad for the normalized projected emittance (εp) and less than 0.8 mm.mrad normalized slice emittances for 80 slices out of 100, for perfect beam conditions and with 0.7 ps rise time on the laser pulse and a 0.3mm.mrad thermal emittance (εth). Combining multiple errors on tuning parameters and emission pulse characteristics, the projected emittance and slice emittances goals remain well within the LCLS requirements for shot-to-shot pulses. In this paper, we present the PARMELA studies performed to design the LCLS photo-injector beamline and study its stability.