The JPL Cryogenic Dilatometer: Measuring the Thermal Expansion Coefficient of Aerospace Materials

Opto-mechanical systems such as the James Webb Space Telescope and the Herschel Space Tele- scope must maintain accurate dimensions over a wide range of temperatures. One piece of in- formation essential to I successful instrument is the thermal expansion coefficient (CTE) of the component materials measured over the expected range of temperatures, Other important data are stability (creep), and for actuators, the stroke as a function of temperature. From room temperature to below 30 K, the JPL dilatometer has measured CTE and creep for a variety of materials including ULE, Zerodur, fused silica, single-crystal silicon, silicon carbide, copper, Invar and PMN actuators. It has also tested the CTE and stroke of piezo-electric actuators. This paper updates the status of the JPL cryogenic dilatometer, presents improved error estimation, and recent measurements of silicon carbide and Invar.