A high-precision dilatometer based on sub-nm heterodyne interferometry

In this paper, we present a high-precision dilatometer for dimensional characterization of highly-stable materials. The dilatometer is based on a highly symmetric heterodyne interferometer where a reference and a measurement mirror are fixed inside a tubular shaped specimen made of the material under investigation. The specimen is placed inside a thermally controlled oven; the temperature can be varied between 20°C and 60°C. We measured the linear coefficient of thermal expansion (CTE) of tubes made of carbon-fiber reinforced plastics (CFRP) and Zerodur, a thermally highly stable glass ceramics. An accuracy ≪10−7 K−1 was achieved.