Force-neutral beams and limiting currents

Abstract

For intense relativistic electron-beam propagation into low-pressure neutral gas in a metallic drift tube, it is shown for typical experimental parameters that the beam leaves the anode only when it is almost space-charge neutral, and that a fully propagating beam occurs only if it is completely space-charge neutral. Ion ionization effects are shown to play a crucial role in the charge-neutralization process, and a new interpretation of existing experimental data is given.