Electrical Breakdown Measurements of Cesium Vapor in a Rhenium Electrode Diode

The electrical breakdown of cesium vapor was measured in a guard-ringed, variable parameter test vehicle, which had plane parallel rhenium electrodes. Experiments were conducted over a range of emitter temperatures from 1300° to 2000°K, with cesium pressures from 0.053 to 6.22 Torr and interrelectrode spacings from 0.001 to 0.07 cm. Because the breakdown occurred at relatively low voltages, the contact potential difference of the electrodes, as a function of temperature and cesium coverage, was taken into account. Paschen-type curves exhibited minima in breakdown potential as a function of spacing at high pressures. At low pressures the necessary large spacings could not be achieved. The maximum breakdown voltage was 6 V at 0.053 Torr and the minimum breakdown voltage was 0.21 V at 6.22 Torr. At low cesium pressures the effect of the emitter temperature is pronounced. When the pressure is constant, the breakdown voltage shifts as a function of emitter temperature. At high pressures, the curves do not vary with emitter temperature at constant pressure, but shift in voltage as the pressure is changed. These experiments indicate that the Paschen behavior is not followed in the case of hot electrode discharges, for all ranges of temperature and pressure.