High-Power Pulse Generation Using Exploding Fuses

Exploding foils provide an opening switch technique that can deliver energy from an inductive store to a resistive load. The work described in this paper derives from that of DiMarco (Los Alamos Scientific Laboratory) who used copper foils to generate ∼ 100 nsec pulses of up to 100 kV. Our objective was to establish the feasibility of generating still shorter pulses (in the 10 to 100 nsec range) with voltages of up to 1 MV. Initial experiments used a 25 kV capacitor bank energy source, similar to that used by DiMarco, charging a stripline inductive energy store provided with distributed capacitance to permit pulse shaping. Subsequent experiments used a 60 kV bank with a 1 nsec risetime, and some tests were conducted using a water capacitor energy store charged to more than 100 kV. In all cases the foils were immersed in liquid to discourage re-strike. A number of scaling laws were postulated and were found to be in general agreement with experiments. Voltages of more than 200 kV were generated in 50 nsec pulses and voltages in excess of 400 kV were generated in 25 nsec pulses. Of the foil materials tested, copper was found to give the best performance. This result is believed to be associated with its low resistivity at room temperatures which suggests that low temperature foils may give still better results. In the time regimes studied, the limits of the technique appear to be maximum voltage gains between five and 6 and pulse duration “compressions” of the order of twenty.