Estimation of plasma parameters in a gas-discharge tube using the terminal characteristics and a transient computer model

A transient computer model is used to estimate plasma parameters in a high-current demountable Cs-Ba tacitron. The model couples the external circuit to the plasma discharge, and calculates electron energy, plasma density, sheath potentials, cesium coverage on the emitter surface, forward voltage drop, and discharge current as functions of time. Fitting the model I-V curve to the measured I-V characteristic of an experimental device provides an estimate for various internal physical parameters using only the terminal characteristics of the device and the reservoir and electrode temperatures. The high-current demountable Cs-Ba tacitron was designed and fabricated at the Russian Scientific Center, Kurchatov Institute, and tested by the University of New Mexico´s Pulsed Power and Plasma Sciences Laboratory as part of a program to develop radiation-hard switching elements for use in space nuclear power applications. In addition to demonstrating high-current operation, testing of this tacitron was intended to provide scaling information for future efforts. Estimates of internal physical parameters, based on the transient computer model, are used to provide greater insight on device scaling.