Design of a W-band second-harmonic TE02 gyro-TWT amplifier

A harmonic gyrotron traveling-wave tube (gyro-TWT) amplifier is described that can stably deliver high peak and average power in the ion-loss TE02-mode at 91.4 GHz, The single-stage second-harmonic TE02 gyro-TWT is predicted to produce a peak power of 600 kW with an efficiency of 24% a saturated gain of 30 dB, and a 3-dB bandwidth of 2.7%. The amplifier employs a 100-kV 25-A electron beam emitted from a magnetron injection gun with v(perpendicular to)/v(parallel to) = 1.2 and Deltav(parallel to)/v(parallel to) = = 8%. The de,ice is based on the proven concept that the electron beam current can be much higher in a stable harmonic gyro-TWT amplifier than at the fundamental due to the relatively weaker strength of the harmonic interaction. The TE02 overmoded interaction waveguide is sufficiently large to handle an average power of 60 kW and provides considerable clearance for the high-current electron beam, An innovative mode-selective interaction circuit prevents the amplifier from oscillating in undesired modes.