Microwave Cavities for Plasma Diagnostics

Abstract

Standard devices used in plasma diagnostics are the microwave interferometer and microwave cavity. The cavities usually used are cylindrical resonators (TM010, TM020, etc.), which present the problem that they “diagnose” a plasma over a relatively long section without taking into consideration local instabilities or fluctuations. In this paper, two types of smallgap cavities are presented: namely, the spherical resonator and the reentrant cavity. Theoretical and experimental results are given and compared with those of a cylindrical resonator.