Computer studies of collective ion acceleration

A relativistic electron beam entering a metallic drift tube filled with neutral gas at low pressure (e.g., 0.1-0.5 Torr ${\mathrm{H}}_2$) creates a potential well which may result in acceleration of ions to several times the beam energy. We have studied this process computationally, with emphasis on the modeling of a number of recent experiments. The code agrees with most of the experimental results, and verifies a recently proposed model for the acceleration process.