A tapered reflection-type gyrotron travelling-wave-tube amplifier (gyro-twt) operating in Ka-band is presently under investigation at NRL. The device incorporates precise axial tapering of both the magnetic field and the interaction circuit for broadband operation. The amplifier operates in the TE10 rectangular waveguide mode at the fundamental cyclotron frequency at a beam voltage of 33 kV and a beam current of 1.6 A. By employing an electron beam with an alpha of around 0.6, small signal gain in excess of 16 dB is observed over a wide instantaneous frequency range (33 %, 27-39 GHz), in good agreement with theory.
G. S. Park,
"Broadband operation of a millimeter-wave GYRO-TWT", Proc. SPIE 1514, 15th International Conference on Infrared and Millimeter Waves, 151456 (1 December 1990); doi: 10.1117/12.2301596; https://doi.org/10.1117/12.2301596