A SENSITIVE DILATOMETER FOR USE AT LOW TEMPERATURES

Abstract

A new dilatometer for the measurement of thermal expansion at very low temperatures is described. It employs a doubly twisted strip which converts the linear expansion of a specimen into a rotation which can be measured with an optical lever. The present limit of detection of the apparatus is about 3 × 10−10 cm change in length of a specimen 8 cm long. So far, measurements have been made only on copper; these indicate that below 8 °K α is given by 3.10 × 10−11T3 + 2.78 × 10−10T/° K. This implies a limiting lattice Grueneisen constant, [Formula: see text], of 1.95, and an electronic γe of 1.21.