TE/sub 21/ second-harmonic gyro-TWT amplifier with an axis-encircling beam

Summary form only given. A second-harmonic TE/sub 21/ gyro-TWT with an axis-encircling electron beam is being constructed at University of California Davis (UCD) that is predicted to double the efficiency of our previous 200 kW, 12% efficient MIG TE/sub 21//sup (2)/ gyro-TWT (Wang et al, Phys. Rev. Lett. vol. 75, p. 4322, 1995), where the superscript refers to the harmonic number. The new device will avoid the loss in efficiency due to off-axis electrons interacting with the resulting linearly polarized node. The amplifier is predicted by our large signal code to produce 50 kW in Ka-band with 20% efficiency, 30 dB saturated gain and 3% bandwidth. The 70 kV, 3.5 A axis encircling beam with v/sub /spl perp///v/sub z/=1.2, /spl Delta/v/sub z//v/sub z/=7%, will be produced by a Cusp electron gun delivered by Northrop Grumman.