Modelling of an RF electron accelerator

The authors report on the modeling of an RF e-beam accelerator, intended to eventually yield a high energy (100 MeV), high current (200's of amps), short pulse (10's of ps), and low emittance (25π mm-mrad, normalized) electron beam for use in a free electron laser. The design approach relies upon RF focusing by photocathode shaping to minimize the number of injector focus solenoids. The simulation code ISIS models particle motion within the first two injector RF cavities, where space charge effects are most significant and need to be treated precisely. Body-fitted coordinates in the ISIS code making modeling variations to the RF cavity shapes particularly straightforward. A scheme for initializing RF cavity fields in ISIS is reported. The particles are followed into the remainder of the accelerator (through RF cavities, solenoids ampersand quadrupole focus magnets, drifts, bends, etc.) using an e-beam accelerator code PARMELA. This combination of codes provides the requisite accuracy and flexibility needed to optimize the large number of design parameters involved