Particle Simulation of Darht-ii Downstream Transport

The DARHT-II beamline utilizes a fast stripline kicker to temporally chop a high current electron beam from a single induction LINAC and deliver multiple temporal electron beam pulses to an x-ray converter target. To obtain a high quality radiographic measurement requires that high beam quality be maintained throughout the transport line from the end of the accelerator through the final focus lens and to the x-ray converter target. Issues that will affect beam quality such as spot size and emittance at the converter target include dynamic effects associated with the stripline kicker as well as emittance growth due to the nonlinear forces associated with the kicker and various focusing elements in the transport line. A particle-in-cell code is utilized to evaluate beam transport in the downstream transport line in DARHT-II. External focusing forces are included utilizing either analytic expressions or field maps. From these simulations, for various initial beam loads based on expected accelerator performance the temporally integrated spot size and emittance can be estimated.