Ion Sampling from the Positive Column of dc Discharges in HeAr Mixtures

摘要

Measurements have been made of the ion species present in the positive column of dc discharges of 0.05% and 0.5% argon in helium, by sampling through a 35‐μ‐diam orifice in the wall of the discharge tube. Data for 0.05% argon has been obtained over a current range of 15–90 mA and for pressures from 3 to 30 Torr. The main ion species observed were Ar+, He+, and He2+. Theoretical analysis combined with measurements of the variation of Ar+ with distance from the cathode, enable estimates to be made of the degree of ionization of Ar, and also an upper limit for the helium metastable particle densities present in the discharge. Metastable density values are, in general, an order‐of‐magnitude larger than the electron densities.