Mechanisms of Positive and Negative Corona in Hydrogen and Argon between Coaxial Cylindrical Electrodes over an Extended Pressure Range

Abstract

Mechanisms in the corona discharge from a fine platinum wire at a positive potential along the axis of a hollow nickel cylinder have been investigated by using the oscilloscope to analyze the pulses caused by α-particles passed through the low field region parallel to the wire. γp, the secondary coefficient for the photo-electric effect at the cathode in hydrogen, had values from 70×10−5 at 100 mm to 5×10−5 at 650 mm pressure. γi for the hydrogen ions at the cathode was less than 10−6. The mobility of the positive ions (presumably H2+) was 13.4 (±0.4) cm2/volt×sec at 760 mm and 20°C. Adding 0.1 to 1.0 percent of oxygen to hydrogen resulted in the formation of O2− ions. γi for the argon positive ions was about 9×10−4 extrapolated to zero pressure and decreased with increasing pressure and γp was less than 110γi. Most of the ions were A2+ with a mobility of 1.94 (±0.08) cm2/volt×sec. Positive wire dc current voltage data were taken in hydrogen and argon at several pressures. Sparks occurred with the positive wire in argon at relatively lower gap voltages than in hydrogen. Current-voltage data were taken with the wire negative. In hydrogen the discharge started as a small (10−11 amp) self-supporting current (probably uniformly distributed along the wire) which changed with increasing gap voltage to a larger (microampere) discharge localized in luminous spots on the wire in analogy to Miller's observations in nitrogen. No small self-supporting currents were observed in argon. The discharge started as a spark above 200 mm and as a glow that spread uniformly over the wire below 100 mm pressure.