Pulsed cathode heating method

A pulsed-mode heating method has been developed and tested for a 1-in.-diameter cathode which reduces the average filament power by over an order of magnitude. The method allows cyclic operation with a few seconds of peak cathode temperature, which allows many microsecond-duration electron pulses to be fired at the peak cathode temperature in each cycle. For a 2-in.-diameter 0.125-in.-thick LaB/sub 6/ cathode, the saving is just as great. A 1.68-mF capacitor at 6 kV can cycle the larger cathode from 494 degrees to 1800 degrees C and back in 120 s. The energy requirement is 30.2 kJ, which is an average power of 252 W. This is still a saving of over an order of magnitude from the case of steady heating. The same cathode thickness as in the 1-in. case is assumed in this prediction.< >