Ion Temperature, Charge Exchange, and Coulomb Collisions in an Argon Plasma Column

Abstract

Ion temperatures in a highly ionized argon plasma column have been measured with a Fabry‐Perot interferometer. Plasma‐column conditions were altered over a range of parameters from 10% to 70% ionized, electron temperature T_e=2–10 eV, and magnetic field 1400–2800 G. In general, T_i is about one‐tenth T_e, determined by the balance between electron heating and charge‐exchange cooling. The measured values of T_i agree fairly well with those calculated, using accepted values of Coulomb collision and charge‐exchange cross sections. Alternately, the present data are processed to derive approximate values of the charge‐exchange cross section to neutral argon as a function of Ar⁺ ion energy in the range 0.1–1.0 eV. It can also be concluded that the theoretical rate for electron‐ion energy relaxation is not seriously in error.