Setup to Measure the Coefficient of Thermal Expansion (CTE) of Ultra Stable Materials at Temperature Range from 100K to 300K

Abstract

For space and terrestrial applications dimensionally highly stable materials are needed, e.g. to enable precise measurements. This property of the ultra stable materials, like glass-­ceramics or composite materials, is characterized by the Coefficient of Thermal Expansion (CTE). Space applications, like optical systems or sensors, often have a wide operating temperature range, where the CTEs of used materials have to be determined also at cryogenic temperatures. The basic of our setup is a heterodyne laser interferometer, that measures length variations of the sample caused by temperature changes. Our setup is an improvement of the existing facility at room temperature and allows to define CTEs at the temperature range from 100K to 300K. The mechanical and thermal design were improved, due to new requirements. The reached accuracy at room temperature is 10ppb/K, which is also the goal for the new setup.