Positive column of Na--Ar and Na--Ne--Ar dc low-pressure discharges

Measurements are reported of the electron temperature, electric field, and electron density in the positive column of low-pressure Na–Ar and Na–Ne–Ar dc discharges. The production of light at the sodium D resonance lines was also measured. The experimental data were obtained for a tube radius of 1.4 cm, and a noble gas filling of 10 Torr. The sodium density varied from 1×1019 to 6×1019 m−3, and the discharge current from 0.1 to 3.0 A. Depletion of sodium ground-state atoms was found to have a decisive effect on the discharge properties at the higher discharge currents. Calculations on a model of the discharge were performed in addition to the measurements. In this model deviations from the Maxwell electron energy distribution were included. The results of the calculations for the electron temperature as a function of current were found to be in good agreement with the experimental data. However, the calculated electric field as a function of current showed qualitative agreement only.