DC-SC Photoinjector with Low Emittance at Peking Univeristy

High average power Free Electron Lasers require the high average current electron beams with the low emittance. The DC-SC photoinjector developed at Peking University, directly combining a DC Pierce gun with an SRF cavity, can produce the high brightness beam with moderate bunch charge and high duty factor. In order to optimize the transverse emittance which sharply increases at the beginning of the DC gun, a carefully design for the DC gap and the cavity shape is needed. In this paper, the simulation of an upgraded design has been performed. This photoinjector, consisting of a DC gap and a 2+1/2 cell SRF cavity, can produce 4.2 MeV electron beams with 100 pC per bunch and 1.1 μm normalized emittance.