Measurement of thermal expansion by double extensometers between 290Â K and 5Â K

We developed an apparatus for the measurement of thermal expansion using double extensometers between 290 K and 5 K. The sample was set vertically in a variable temperature cryostat and its expansion or contraction was measured using the extensometers directly attached to the sample. The temperatures of the samples were controlled with He gas from the cryostat and a heater wounded around the sample chamber. In order to ensure the validity of this system, we measured the thermal expansion of Ag plates with different thicknesses. As a result, the measured thermal expansion curves were confirmed to show good agreement with each other for Ag plates with thickness of 3 mm, 1 mm and 0.2 mm. Good agreement was also ensured for the curves measured during both the cooling and warming processes. These results suggest that our system will be applicable for superconducting composites with a cross-section as small as 1 mm2.