General plasma characteristics of a Berkeley multifilament ion source

Abstract

The general plasma characteristics of a Berkeley Multifilament Ion Source are presented. The measurements are obtained via a pulsed electrostatic‐probe data‐acquisition system, and in part conclude: (a) The electron distribution function consists of a bulk component of thermal electrons (kT_e∼3–5 eV) comprising 90–97% of the total electron population (depending on operating conditions), plus a nonthermal high‐energy tail, which is a monotonically decreasing function of energy, and contains a small but experimentally significant electron population at energy values 10–15 eV above maximum cathode fall. (b) Overall source performance, i.e., the spatial distribution of plasma potential, plasma density, and ion current density, approximately follows steady‐state low‐pressure discharge theory assuming spatially uniform ion production.