Simulations of high-brightness rf photocathode guns for LLNL-SLAC-LBL 1 GeV test experiment

An ideal rf photocathode gun in a π-mode configuration supporting only a single mode with no nonlinear rf field is studied numerically by using the simulation code PARMELA. For a given electron bunch, the normalized emittance can be minimized. Both the minimum normalized emittance and the optimized accelerating field are proportional to the square root of the peak current. Three possible rf photocathode guns for LLNL-SLAC-LBL 1 GeV test are simulated. It is found that both a 2 ps half-width bunch and a 6 ps half-width bunch with the transverse emittance roughly 8–17 mmm mrad and 1 nC charge per bunch can be generated by guns with (1) ƒ = 1269 MHz , E 0 = 30 MV/m; (2) ƒ = 1269 MHz , E 0 = 60 MV/m; and (3) ƒ = 2856 MHz , E 0 = 60 MV/m. Here, ƒ is the rf frequency, and E 0 is the peak accelerating field.