Pre-ionization studies on the modular theta-pinch experiment for field-reversed configuration applications

Abstract

A new semi-empirical model is introduced for the quantification of inductively-coupled breakdown systems. The model is informed by breakdown studies conducted on the Modular Theta-pinch eXperiment (MTX). Observations made of inductively-coupled breakdown behaviour are consistent with the model's expectations, indicating that the model can be used to aid in design of inductively-coupled pre-ionization systems. The model is further found to be capable of quantifying the efficacy of seed ionization in inductively-coupled systems. Comparisons are made between the standard ringing-theta and a new field-aligned dipole pre-ionization systems. In the presence of sufficient seed ionization, no physical reason was observed for selection of one method over the other, leaving only engineering considerations as the determining factor for selection of an appropriate pre-ionization system. This work is supported by the Institute for Critical Technology and Applied Science (ICTAS) at Virginia Tech and the National Nuclear Security Administration of the U.S. Department of Energy. LA-UR-24-31269