Operation of a Large-Orbit High-Harmonic Gyro-Traveling-Wave Tube Amplifier

Absfracf-The high-harmonic gyro-traveling wave tube (gyro-TWT) is a high-power ( 2 1 kW) millimeter wave amplifier based on the synchronous interaction of a beam of lafge-orbit axis-encircling electrons with a high-order cylindrical waveguide mode. Since the interaction occurs at a high harmonic of the cyclotron frequency, the intense magnetic fields required for the conventional fundamental-mode gyro-TWT are not required. A proof-of-principle experiment designed to demonstrate the interaction of a 150-mA 350-keV electron beam with the TE8, mode of a cylindrical waveguide is described. Principal results include a small signal gain of 10 dB, an interaction bandwidth of 4.3 percent, and a saturated power transfer from electron beam to wave of 0.5 kW. Additional measurements include the dependence of gain on electron beam current and the measurement of the beam’s y, PI, PI,, and A PIl. Sufficient agreement between the experimental results, simulation codes, and an analytic description of the interaction is demonstrated to permit the design of high-performance millimeter wave amplifiers.