Ka-band second-harmonic cusp-gun gyro-TWT

Summary form only given, as follows. A 30 GHz second-harmonic sliced smooth-bore TE/sub 21/ gyro-TWT with a cusp gun has been designed to double the efficiency of our previous 200 kW, 12% efficient, MIG TE/sub 21//sup (2)/ gyro-TWT. The new circuit is also sliced to destroy the odd-order azimuthal modes, but the axis-encircling electrons are no longer be confined to the maxima and minima of the linearly polarized mode. The 70 kV, 3.5 A, v/spl perp//v/sub z/=1.2, /spl Delta/v/sub z//v/sub z/=8%, axis-encircling electron beam is produced by a cusp gun delivered by Northrop Grumman. The single-stage amplifier is predicted by our large-signal simulation code to generate 50 kW at 30 GHz with 20% efficiency, 30 dB saturated gain and 3% constant-drive bandwidth. Linear theory has been used to determine the threshold start-oscillation beam current for absolute instability and the critical section lengths for the potential harmonic gyro-BWO interactions.