A new method for measuring heat of electron evaporation from thermionic energy converter emitter

The method described is based on measuring the rate of emitter cooling after the thermionic energy converter is switched from the open-circuit steady-state operation into the current mode of operation at a constant input power. The rate of change in useful voltage across the electrodes is measured for 0.5 s. During this time useful voltage changes, depending on the current density, from a few to dozens of megavolts. For a current below the kink point of arc voltage-current characteristic where useful voltage is linearly related to the emitter temperature, this corresponds to a definite change in the temperature. The amount of power carried off from the emitter by the current Q _e is determined by a formula. The analysis of measurement errors revealed that they do not exceed 3%. Dependences Q_e on current density, emitter temperature, collector temperature, and cesium vapor pressure are obtained from the measurement. The heat of electron evaporation from the emitter does not depend on the collector temperature, whereas the heat of electron condensation on the collector is independent of the emitter temperature for currents below the kink point of the voltage-current function. With an increase in the cesium vapor pressure the evaporation heat decreases and the heat of condensation passes through the minimum