Ion Source for Low-Energy Collision Studies

An ion source is described which produces either positive or negative ion beams by electron bombardment of a jet of gas at relatively high pressure. The electrons are confined to an ionization region by a reflection-collimation geometry. The ion currents produced are moderate (∼10−9 A) but the ion beams are very stable and noise-free, and have a small spread in kinetic energy as required for low energy collision studies. Most of the data presented pertains to negative ions, although some positive ion results are given.