A model for the positive columns of dc low-pressure discharges in Cs-Ar mixtures, which includes radial depletion of Cs ground-state atoms and radiation trapping, is presented. The available experimental data for this discharge system were extended in such a way that comparison could be made between model calculations and experiments for a wide range of discharge currents and Cs vapor densities (0.2 X 10 19 _3.0 X 10 19 m-3 ) and a reasonable agreement is obtained.

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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 20°C, and sodium density (2.4–5.7)  × 1019 m−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.