A comparison of the effect of radiation on the thermal conductivity of sapphire at low and high temperature

Technical Report · Thu Sep 01 04:00:00 EDT 1994

OSTI ID:47779

White, D P ^[1]

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1. Oak Ridge National Lab., TN (United States)

It has been proposed that sapphire be used in insulating feedthroughs and windows in radiofrequency and microwave heating systems in fusion reactors. The degradation of the thermal conductivity of sapphire with irradiation is a concern in the design of these windows. It has been proposed to cool microwave windows to liquid nitrogen temperatures to take advantage of the thermal conductivity peak, which occurs at approximately 30K in unirradiated sapphire, and the lower dielectric loss tangent at these temperatures. In this paper the methods used to calculate the thermal conductivity and the changes which occur with changes in point defect concentration will be reviewed and the results of the low temperature calculations will be compared to the high temperature calculations. It is found that vacancy scattering can significantly reduce the thermal conductivity over a wide temperature range; for example, a vacancy concentration of 0.01 per atom leads to a fractional change of about 90% at 77K versus 43% at 400K. This reduction has significance for the design and placement of radio frequency and microwave windows in fusion reactors.

• Research Organization: Oak Ridge National Lab., TN (United States)
• OSTI ID: 47779
• Report Number(s): DOE/ER--0313/16; ON: DE95003404
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
IRRADIATION
PHYSICAL RADIATION EFFECTS
PROGRESS REPORT
SAPPHIRE
THERMAL CONDUCTIVITY
THERMONUCLEAR REACTOR MATERIALS