Resonant Reflectors for Experimental Studies of the Reflected-Signal Influence on the Gyrotron Operation Regimes

Abstract

Experimental study of the influence of resonant reflection of the operation mode on the gyrotron generation regimes is a topical problem of modern high-power vacuum electronics. In this work, we formulate the requirements for the external resonant reflection system and propose its development variants. We consider resonant reflectors of two types, which are intended for experiments with a gyrotron at the operation mode TE0, 2 at a frequency of 28 GHz. According to the initial requirements, the reflection coefficient of the gyrotron operation mode at the resonant frequency should amount to 5–10% with the reflector quality factor exceeding 15000 in the range 27998–28008 MHz of the gyrotron-frequency tuning by a magnetic field. The first variant of the reflector is a cylindrical cavity at the TE0, 3, 1 mode. The measured reflection coefficient amounted to 6% at a frequency of 27999 MHz with a quality factor of 15000. The tunable two-mirror resonator at the mode TEM0, 0, p (p >> 1) is the second variant. A number of the waveguide converters of the circular-waveguide mode TE0, 2 to the TE0, 1 mode, the TE0, 1 mode to the TE1, 1 mode, and the convertor of the TE1, 1 mode to the linearly polarized Gaussian wave beam are developed and manufactured for excitation of a two-mirror resonant reflector by the gyrotron radiation. During the frequency tuning in the band 27990–28010 MHz, the measured reflection coefficient amounted to 8% with a quality factor of about 40000. The calculated and measured converter characteristics are given along with the measured frequency characteristics of the developed resonant reflectors.