W-band gyro-devices using helically corrugated waveguide and cusp gun : design, simulation and experiment

He, W. and Donaldson, C. R. and Li, F. and Zhang, L. and Cross, A. W. and Phelps, A. D. R. and Ronald, K. and Robertson, C. W. and Whyte, C. G. and Young, A. R. (2011) W-band gyro-devices using helically corrugated waveguide and cusp gun : design, simulation and experiment. Terahertz Science & Technology, 4 (1). pp. 9-19. (https://doi.org/10.11906/TST.009-019.2011.03.02)

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Abstract

This paper presents the design and simulation of W-band Gyro-devices using helically corrugated waveguides as the beam-wave interaction region and a cusp gun as the electron beam source. The electron beam system and the beam-wave interaction were optimized through numerical simulations by using a particle-in-cell (PIC) code MAGIC to predict (calculate) the output power and frequency bandwidth. The beam cross sectional measurement using a scintillator plate confirmed that an axis encircling electron beam was achieved with the designed beam parameters of current 1.5 A and energy 40 keV. The W-band helically corrugated interaction region for the gyrotron backward wave oscillator (Gyro-BWO) was manufactured with a dispersion from 80 GHz to 110 GHz measured using a vector network analyser which was found to be in good agreement with simulations and theory. The Gyro-BWO achieved frequency-tuneable operation by adjusting the magnetic field in the interaction cavity. A -3 dB bandwidth of ~84-104 GHz and output power ~10 kW were simulated using the electron beam from the cusp gun. The gyrotron travelling wave amplifier (Gyro-TWA) is designed to have a -3 dB frequency bandwidth of 90-100 GHz, output power of 10 kW and saturated amplification gain of 40 dB.