Beam emittance simulations for high gradient pulsed dc/rf gun

One of the most important targets for building modern accelerators is to increase their brightness. The purpose of building a pulsed dc/rf gun is to seek high charge bunch and low beam transverse emittance injection for subsequent acceleration. These, together with a short bunch length, are key factors for enhancing brightness of accelerators. In this paper, we will present the simulation results of the beam emittance changes in dc/rf guns under different gun voltages. SUPERFISH code and PARMELA code were used to simulate the beam dynamic process in the gun. These simulations indicate that smaller beam transverse emittance (< 0.5 mm.mrad) can be obtained when the voltage on the dc gap is lower than 200 kV and the bunch charge is at 200 pc, and increasing the dc gap voltage will greatly improve the emittances.