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 Te=2–10 eV, and magnetic field 1400–2800 G. In general, Ti is about one-tenth Te, determined by the balance between electron heating and charge-exchange cooling. The measured values of Ti 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.