Linear Thermal Expansion Measurements of Single Crystal Silicon for Validation of Interferometer Based Cryogenic Dilatometer

Abstract

Linear thermal expansion measurements were performed for high‐purity P‐type single crystal silicon over a temperature range of 30K to 310K to validate the accuracy of JPL’s interferometer‐based Cryogenic Dilatometer Facility. This system was developed to better characterize thermophysical properties of precision engineering materials at cryogenic temperatures for space‐based optical systems. An accurate measurement of these properties is critical for the success of missions such as the James Webb Space Telescope and the Terrestrial Planet Finder Coronagraph where picometer‐level instabilities and thermal deformations impact performance. Results from these single crystal silicon measurements show a mean system repeatability of 4 ppb/K in the coefficient of thermal expansion (CTE) from 35K to 305K. Comparison with NIST/CODATA recommended values shows agreement of better than 2 ppb/K from 30K to 80K, better than 11 ppb/K from 80K to 165K, and better than 2 ppb/K from 165K to 305K.