EXPLOSIVE CATHODE GYROTRON EXPERIMENTS

Experiments have investigated the behavior of explosive emission catho de gyrotrons using cylindrically symmetric coaxial diodes with central ly located knife-edged cathode and conical anode. Voltage probes and c urrent shunts were exploited to monitor the diode electrical behavior when driven by a 3 mu s 1/e time Marx power supply (up to 150 kV), Tem poral reference signals permitted comparison of the diode's electrical evolution with the simultaneously measured microwave output signal fr om the gyrotron, The microwave output pulse duration was found to depe nd on the diode gap spacing (in the range 16-27 mm), the cavity magnet ic field (range 1.3-3.3 T) and the cathode material, the termination b eing caused by the decay of the accelerating potential across the diod e and the disruption of the diode geometry. The ratios of the cathode hare expansion velocities for graphite, copper and stainless steel cat hodes were estimated as (1:(1.3+/-0.2): (2.2+/-0.5)) with a correspond ing change in the duration of the microwave output signal [((590+/-17) : (414+/-25): (325+/-10)) ns at 2.6 T], Preliminary results are report ed of recent experiments which have compared the optical emissions fro m the diode region during pulsed gyrotron operation with the simultane ously recorded diode electrical behavior and the gyrotron microwave ou tput.