Explosive cathode gyrotron experiments

Abstract

Experiments have investigated the behavior of explosive emission cathode gyrotrons using cylindrically symmetric coaxial diodes with centrally located knife-edged cathode and conical anode. Voltage probes and current shunts were exploited to monitor the diode electrical behavior when driven by a 3 /spl mu/s 1/e time Marx power supply (up to 150 kV). Temporal reference signals permitted comparison of the diode's electrical evolution with the simultaneously measured microwave output signal from the gyrotron. The microwave output pulse duration was found to depend on the diode gap spacing (in the range 16-27 mm), the cavity magnetic field (range 1.3-3.3 T) and the cathode material, the termination being caused by the decay of the accelerating potential across the diode and the disruption of the diode geometry. The ratios of the cathode flare expansion velocities for graphite, copper and stainless steel cathodes were estimated as (1:(1.3/spl plusmn/0.2):(2.2/spl plusmn/0.5)) with a corresponding change in the duration of the microwave output signal [((590/spl plusmn/17):(414/spl plusmn/25):(325/spl plusmn/10)) ns at 2.6 T]. Preliminary results are reported of recent experiments which have compared the optical emissions from the diode region during pulsed gyrotron operation with the simultaneously recorded diode electrical behavior and the gyrotron microwave output.