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Precision Measurement of Low Loss Window Materials

Published online by Cambridge University Press:  01 February 2011

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Abstract

A precision measurement technique for measuring complex dielectric permittivity in the 118 – 178 GHz frequency range is described. The combination of a high-quality Fabry-Perot resonator, excited by a free-running BWO (backward wave oscillator), combined with the processing capability of a sensitive receiver based on the Tektronix 2782 spectrum analyzer, using the WM782 (F-G) harmonic mixer, yields a very sensitive measurement technique.

The development of techniques for measuring extremely low losses in dielectric materials has been driven primarily by the requirements of the fusion energy research program. The heating of a plasma to the temperatures required for fusion is expected to require the delivery of megawatts of RF power through vacuum windows into the plasma vessel. A material with very low loss as well as excellent thermal and mechanical properties must be utilized to avoid a catastrophic window failure.

The relevant loss mechanisms and measured results for several candidate materials are discussed

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 833: Symposium G – Materials, Integration, and Packaging Issues for High-Frequency Devices II , 2004 , G2.8
Copyright
Copyright © Materials Research Society 2005

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References

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