Design of an 85 GHz TE1,3phase-locked gyroklystron oscillator experiment

The design is described of an 85 GHz TE1,3 phase-locked gyroklystron oscillator experiment. The purpose of the experiment is to study the physics issues associated with ultra-high power highly overmoded phase-locked gyroklystron oscillators. The problems of mode conversion losses at cavity boundaries and self-oscillation of the input cavity presented the most challenging aspect of the design. A WKB type theory of mode conversion losses in highly overmoded waveguide cavities had to be developed to quantify design trade-offs. Three input cavity designs with varying degrees of design risk with respect to mode conversion losses were fabricated and cold tested. Two cavities with conservative designs were found to perform very close to expectations.