Switch evaluation test system for the National Ignition Facility

Flashlamp pumped lasers use pulsed power switches to commute energy stored in capacitor banks to the flashlamps. To lower the total cost of these switches, Sandia National Laboratories has a research program to evaluate large closing switches. The particular application in which we are interested is the National Ignition Facility (NIF), being designed by Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and Sandia National Laboratories. The target value of the energy switched by a single device is 1.6 MJ, from a 6 mF, 24 k V capacitor bank. The peak current is 500 WI. The lifetime of the NIF; facility is 24 thousand shots. There is no switch today proven at these parameters. Several short-lived switches (100's of shots) exist that can handle the voltage and current, but would require maintenance during the facility life. Other type devices, notably ignitrons, have published lifetimes in excess of 20 thousand shots, but at lower currents and shorter pulse widths. The goal of the experiments at Sandia is to test switches with the ill NIF wave shape, and at the correct voltage. The Sandia facility can provide over 500 kA at 24 kV charge voltage. The facility has 6.4 mF total capacitance, arranged in 25 sub-modules. The modular design makes the facility more flexible (for possible testing at lower current) and safer. For pulse shaping (the NIF wave shape is critically damped) there is an inductor and resistor for each of the 25 modules. Rather than one large inductor and resistor, this lowers the current in the pulse shaping components, and raises their value to those more easily attained with lumped inductors and resistors. We will show the design of the facility, and show results from testing conducted thus far. We will also show details of the testing plan for high current switches.