Hydrogen Spark Gap For High Repetition Rates

The Pulsed Power Technology Branch at NAVSWC is investigating high-power switch technologies. In- house efforts have concentrated on spark-gap switches because of their high-voltage and high-current capabilities in single-shot devices and because of their simplicity and low cost. We have found that using hydrogen gas, with its high thermal diffusivity, allows an order-of-magnitude improvement in the recovery time (and, therefore, repetition rate) of an unblown spark-gap switch. Recovery of the switch can be made even faster by triggering the switch well below its self-break voltage, allowing voltage to be reapplied while the gas is still hot. Tests have shown that recovery times (to the operating voltage) can be reduced an order-of-magnitude when the gap is undervolted by approximately 50%. Recent tests have demonstrated 100-microsecond recovery of an undervolted hydrogen spark gap at voltages up to 120 kV, peak currents up to 170 kA, and energies up to 12 kJ. Plans are underway to test the switch to 500 kV.