Electric Field and Breakdown Modeling of Helical Explosive Generators

At the 14th International Conference on Megagauss Magnetic Field and Related Topics (MG-XIV) Chase et al reported on modeling electrical breakdown in helical explosive generators [1]. The onset of electrical breakdown between stator and armature was predicted to occur just ahead of the advancing shock front of the expanding armature. A special set of generators was constructed without the usual stator wire insulation, so that the nitrogen fill gas was the only dielectric in the system. In this simplified configuration it was possible to predict when and where electrical breakdown would occur and benchmark the model. In this paper we describe the technique used to calculate the internal electric fields in helical generators, including the cases of only gas insulation and gas plus solid dielectric at the stator. The electric field model has been incorporated into the CAGEN explosive generator modeling code [2-4] and applied to the LLNL Mini-G [5,6] helical generator design.

I. Introduction

Magnetic flux compression generators (FCGs) powered by high explosives (HE) were invented in the former Soviet Union and the United States more than 50 years ago. Because of the large energy density of HE (approximately 5 MJ/kg), conversion from chemical energy to electrical energy can be accomplished with relatively small (less than 1 m characteristic size) devices.