Three kilojoule, one hertz modulator

A 300 kV, 10 kA, spark-gap switched line-type modulator with a pulse width of 1 μs and a repetition rate of 1 Hz has been designed and constructed and is operational. An excellent flat-top pulse has been achieved. The output impedance is only 30 Ω. Two parallel 8:1 transformers are used, each with two parallel networks connected at the primary. Each of the four 1.9 Ω networks contains seven capacitors positioned for minimal return inductance. Each pair of adjacent capacitors is connected by four parallel inductors, to allow easy adjustment of both mutual and self-inductance. Variable series and parallel resistors allow further flexibility. The modulator is interfaced to a high-power microwave vacuum tube by an epoxy-cast high-voltage bushing. Voltages are monitored by two different types of custom-made voltage probes. The charging supply has been custom-modified to allow nearly a 1 Hz repetition rate