The Positive Ion Current at the Cathode in the Glow Discharge

Abstract

The positive ion current passing through a perforation in the cathode of a glow discharge tube has been measured with various types of collectors and the factors influencing the ratio of positive ions to total current studied. At pressures above 0.5 mm the positive ion current constitutes but a small fraction of the total current, while at lower pressures it increases inversely with the pressure, reaching approximately half the total current below 0.01 mm. The fraction of the current carried by positive ions is independent of the size and shape of the perforation, of the current passing through the discharge, and of the position of the anode provided it is not within a certain critical distance from the edge of the Crookes dark space; it does, however, vary with the gas, increasing for decreasing molecular weight.