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

A harmonic gyrotron traveling-wave tube (gyro-TWT) amplifier is described t hat can stably deliver high peak and average power in the ion-loss TE02-mod e 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 gai n 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(perpendicula r to)/v(parallel to) = 1.2 and Deltav(parallel to)/v(parallel to) = = 8%. T he 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 fundame ntal due to the relatively weaker strength of the harmonic interaction. The TE02 overmoded interaction waveguide is sufficiently large to handle an av erage power of 60 kW and provides considerable clearance for the high-curre nt electron beam, An innovative mode-selective interaction circuit prevents the amplifier from oscillating in undesired modes.