Electrical conduction and breakdown in argon and helium at temperatures from 1500°K to 2500°K

Characteristic current/voltage curves have been obtained for inert gases at high temperature and pressure between coaxial graphite electrodes. Argon and helium of commercial purity have been investigated at pressures from 1 to 2 atmospheres and in the temperature range 1500¿2500°K. The geometry chosen was such that the gases and the electrodes were in approximate thermal equilibrium. 400 c/s alternating voltages (up to 500 V peak) were applied to the electrodes, and breakdown occurred at voltages which decreased rapidly as the temperature increased. Below about 2000°K, sharp transitions were observed to either glow-or arc-type discharges. Above this temperature, thermionic emission from the electrodes controlled the form of the characteristic which could be separated into four well defined regions. The initial slopes of the characteristics indicate high effective conductivities, which are believed to be partly associated with the dynamic nature of the characteristics.