Analysis of the Possibilities to Control Diffraction Quality Factors of the Cavities of Subterahertz Gyrotrons

Abstract

Manufacturing of cylindrical cavities for shortwavelength gyrotrons is usually performed with micrometerscale precision. In subterahertz (sub-THz) and terahertz (THz) gyrotrons, this often results in the fabrication of slightly up-tapered cavities instead of the cavities having the central parts of a constant radius. Correspondingly, the diffractive quality factors (Q D-factors) of such slightly conical cavities may differ from those calculated for the cavities with constant radius central parts. We show that the sensitivity of Q D-factors to the cavity fabrication can be mitigated by introducing some local nonuniformities at the end of a slightly conical up-tapered section of the cavities. The proposed approach is illustrated with an example of a gyrotron designed for spectroscopic applications and having an output radiation power of tens of watts at the frequency of 0.527 THz. This article presents some numerical modeling results, which show how proposed local nonuniformities reduce the sensitivity of Q D-factors to defects in fabrication.

Improvement of the Output Mode Purity of a Complex-Cavity Resonator for a Frequency-Tunable Sub-THz Gyrotron

“…Irises in cavities of sub-THz gyrotrons have been applied mainly to enhance the diffractive quality factor of the resonators [2], [13]- [15]. Here, we use a radial stub to improve the output mode purity.…”