High voltage trigger-pulse generator for marxes and plasma foci

We report the design and implementation of a reversible, square-pulse generator for triggering spark gaps. It employs coaxial cables for charge-storage and pulse formation, and a thyratron as the switch. The generator has a nominal output voltage 5–30 kV, and a pulse length governed by the cable’s physical length. Two variants are presented: 1) single-stage one consisting of one charged cable that is discharged with a thyratron, 2) two-stage having an inverting circuit that uses a second coaxial cable to reverse the polarity of the pulse produced by the first one. Since the cables employed were wound solenoid-like special insulation was devised to avoid breakdown between adjacent coils in the winding when the pulses propagate along the shields of the cables. The rise-time obtained is mostly dictated by the switching time of the thyratron; with the one we used in the tests, rise-times in the range 30–40 ns were obtained. We present the results obtained in the application of the generator to triggering a Marx generator and a plasma focus.