Glow discharge in hydrogen-water vapor mixture

Abstract

Summary form only given, as follows. A glow discharge in hydrogen is widely used in various modifications of the ion sources for generation of both H/sup +/ and H/sup -/. The paper is devoted to experimental investigations of plasma parameters of a positive column in hydrogen and water vapor mixture. The discharge was fired between two parallel 15 mm diameter Mo electrodes with 80 mm separation in a 15 mm inner diameter quartz tube. The total gas pressure and discharge current were changed between 0.2-2 Torr and 10-30 mA respectively. The electron temperature (T/sub c/) was measured with a Langmuir probe. The excitation temperature (T/sub exc/) was estimated from the intensity ratio of the emission lines H/sub /spl gamma//, and H/sub /spl delta//. It was shown that this temperatures depends strongly on the amount of H/sub 2/O due to the vibrational collisions between electrons and H/sub 2/O molecules. When the water vapor concentration was optimal, we observed a significant decreasing of T/sub e/ and T/sub exc/ in comparison with the pure hydrogen case (4-5 times). It is essential for the H/sup -/ generation because the cross section for the reaction of dissociative attachment H/sub 2//sup +/+e=H/sup +/+H/sup -/ is inversely proportional with the electron temperature.