Precision characterization of gyrotron window materials. Final report, September 1, 1995--April 30, 1997

An optical resonator has been constructed to measure dielectric properties of materials at millimeter wavelengths. The objectives are the identification and loss measurements of window materials for high power gyrotrons. The source of radiation is from a backward wave oscillator (BWO) with enhanced power, good stability, and spectral purity. The measurement technique is based on the application of a high Q Fabry-Perot resonator which provides a means of determining the difference in the reciprocal Q-factors with high accuracy. Initial loss measurements at 150 GHz at room temperature are performed on sapphire. Preliminary loss tangent results on sapphire is found to be around 10{sup {minus}4} and are reported here. Work is in progress to develop a system which will scan the resonance rapidly to produce a measurement in less than a minute and to measure the loss as a function of temperature