On Calculation of the Ignition Voltage for a Back-Arc Discharge in a High-Voltage Thermionic Diode

Abstract

Development of large spacecraft propulsion units involves the creation of high-temperature radiation-resistant systems for current conversion based on thermionic devices of plasma electric power engineering, such as grid-controlled switches and high-voltage plasma thermionic diodes (HVPTD). The current conversion system (CCS) is required to match the electrical parameters of a thermionic conversion power reactor (with an output voltage of 120–150 V) with the parameters of the electric jet engine (having a working voltage of hundreds or thousands of volts). This brings about an urgent issue of calculating the ignition voltage for the back-arc discharge in the interelectrode gap (IEG) of HVPTDs. A semiempirical correlation is proposed for predicting the back-arc discharge ignition voltage as a function of the cesium vapor pressure in IEG and the anode temperature. It can be used by designers of thermionic plasma power engineering devices.