A COMPACT ONE-HALF MV REP-RATE PULSER

Abstract

A rep-rate pulser system has been developed for use in an Army high power test facility. This paper presents final test results of the pulser's performance, The pulser system contains an SCRcontrolled power supply which charges a 55 pF filter bank to voltages up to 50 kV. The power supply can provide up to 300 kW in one second bursts for rep-rate operation. This bank is switched with ignitrons into a second capacitor bank which resonantly charges to 80 kV and stores the maximum energy of 33 kJ. This bank is then switched with a pair of low inductance, simultaneously triggered gas switches into the primary of a step-up 1:13.5 iron-core pulse transformer. The transformer's core is reset by the pulse charging current to the 10.4 pF capacitor bank. The output of the transformer resonantly charges a 56 nF PFN to the maximum voltages of 1 MV in 7 ps. At 90% of peak, a self-breaking output switch closes and the PFN discharges into a 5 resistive load. The stored PFN energy is thus 28 kJ. The pulser section, extending from the primary capacitors to the resistive dummy load is contained within an oil tank. The pulser was tested in single-pulse and at reprates to the full PFN voltage of 1 MV. The specified 500 kV load voltage was achieved without breakdown or corona. Tests were conducted with full voltage at rep-rates up to 1 Hz and with 90% of full voltage, at rep-rates up to 3 Hz. Rep-rate in the maximum voltage range was limited by the capabilities of the DC power supply rather than by the pulser. A 10 to 90% voltage risetime of approximately 35 ns was obtained across the low inductance 5 L2 resistive load. The pulsewidth of the flat-top, an important parameter for this pulser, was 450 ns within an amplitude range +5% of peak. The input power and the pulser triggering were controlled with a Macintosh IIcx computer using LabVIEW (National Instruments) software. This computer accepts commands which allows the pre-setting of all essential pulser parameters, including rep-rate, number of shots, burst width and the amplitude and timing of voltages and currents within the power unit. The LabVIEW control program also incorporates fault detection and display routines.