Helically corrugated interaction regions for W-band gyrotron-Traveling Wave Amplifiers

The helically corrugated interaction region (HCIR) is able to produce an almost ideal dispersion for microwave oscillators/amplifiers. The HCIR is studied and presented in this paper with particular application in a W-band broadband, kWlevel gyrotron traveling wave amplifier (gyro-TWA). The dispersion of the waveguide was calculated, and measurements of a manufactured HCIR showed good agreement with predictions. Numerical simulations of the beam-wave interaction in different circuits showed stable output can be achieved in two gain regions separated by a sever (with purposeful reflections at each end of the circuit). The demonstration of a gyro-TWA based on the HCIR is described with a 3-dB bandwidth of over 5.5 GHz with more than 3.4 kW and the gain was around 36-38 dB. The work presented in this paper will widen the capability of the gyro-TWA from single pulse to high PRF operation.