LSP Simulations of the Neutralized Drift Compression Experiment

The Neutralized Drift Compression Experiment (NDCX) at Lawrence Berkeley National Laboratory involves the longitudinal compression of a singly-stripped K ion beam with a mean energy of 280 keV in a meter long plasma. We present simulation results of compression of the NDCX beam using the PIC code LSP. The NDCX beam encounters an acceleration gap with a time-dependent voltage that decelerates the head and accelerates the tail of a 500 ns pulse which is to be compressed 130 cm downstream. Results show good longitudinal compression without significant emittance growth, but a time-dependent focal length limits the beam radius. An explanation is given for the sizable defocusing effect of the voltage gap. An envelope calculation including the time-dependent focusing effect is in good agreement with the LSP simulations.