Analysis of helical generator driven exploding foil opening switch experiments

The paper presents results from experiments in which a 1 MJ helical flux compression pulsed power generator was used to power an exploding-foil opening switch. Although the high reproducibility of the generator performance enabled the experiments to be performed successfully, the time variation of the fuse voltage confirmed earlier work showing the different fuse behaviour when fed at the reduced energy input rate provided by a flux compressor. Consideration of the experimental data, using an empirical model for the copper foils obtained from fast capacitor bank experiments, showed that the predictions are only accurate until the fuse begins to vaporise. The knowledge gained will enable better fuse designs for flux compression conditioning to be produced, but a complete understanding of the post-burst fuse behaviour must await a detailed theoretical approach which is under development elsewhere. The paper concludes by describing a novel circuit arrangement, which avoids the post-burst fuse behaviour. Automatically operating opening and closing exploding-foil switches are used to provide the conditioning required to drive a very fast high-impedance load.