High voltage generator with fast risetime for EMP simulation

The 1-MV EMP simulator at WWDBw, Munster, Germany, was developed during the late 1970s. The pulsed power system, supplied by Physics International Company (PI) of San Leandro, CA, includes a Marx generator and a peaking circuit/transmission line pulse launch system contained within a plastic housing (gas box) filled with the insulating gas R-12 (freon). Two major concerns have developed over the years since the WWDBw simulator was first dedicated: (1) the venting of freon-12 into the atmosphere is considered harmful to the natural environment, and (2) the most recent EMP studies show that simulated field risetimes might need to be considerably faster than the 10 ns requirements of ten years ago. WWDBw has contracted with PI to provide modifications as necessary to eliminate R-12 from the gas house and to design and develop a pulser providing faster risetimes. PI´s modifications have achieved reliable, reproducible operation at 970 kV in an air environment with risetimes less than 7 ns. In addition, PI has designed, fabricated and tested a pulser for risetimes of 1 ns, 300 to 500 kV output voltage, and 30 to 100 ns pulsewidth. The pulser is compatible with the 1 MV pulser interface so that either pulser can be used to drive the 90 /spl Omega/ waveguide. The fast risetime pulser uses the existing Marx to charge a transfer capacitor similar to the existing peaking capacitors. Upon closure of the transfer switch, a very low inductance peaking capacitor is charged. Subsequent closure of a low inductance output switch launches the fast risetime wave.