Positive column of Na‐Ne‐Ar ac discharges

The positive column of 50-Hz ac discharges in a mixture of sodium vapor and noble gas (99 vol% Ne--1 vol% Ar) has been investigated experimentally. The experimental conditions were as follows: discharge tube radius 10 mm, noble-gas pressure 5.5 Torr at 20degreeC, and sodium density (2.4--5.7) x 10/sup 19/ m/sup -3/ which corresponds to a tube wall temperature of 519--538 K. The rms values of the current ranged from 0.25 to 1.5 A. The discharge properties, measured with the aid of electrostatic probes, show hysteresis effects especially for high rms current values. This behavior can be explained from the combined effects of depletion of sodium atoms and diffusion. It is found that the experimental data on the time-resolved electron temperature agree with calculated values. Qualitative agreement is obtained between the measured and calculated data on the electron density, electric field strength, and radiated power. (AIP)