Ceramic materials for microwave windows

Abstract

Ceramic materials selected for the study of their properties relevant to gyrotron windows are presented. Models for their performance in high frequency and high power gyrotrons show that the materials are to be operated at the limits of their capabilities. Dielectric measurements which determine the dielectric loss tangent in the range from 30-200 GHz and which are used for low loss ceramics -are reviewed, and some results are given. The application of a Fabry-Perot resonator system for measuring tan S in ceramic discs is reported, and first results compared to present data. Methods in use for the mechanical and thermophysical characterization are presented. Evaluation and interpretation of four point bending tests are summarized along with the results from thermal conductivity and thermal shock measurements.