Apparatus for the absolute measurement of the linear thermal expansion coefficient of solids over a wide temperature range

Abstract
Apparatus is described for the automatic measurement of the linear thermal expansion coefficient of solids over the temperature range 80 to 800 K by an absolute interferometric technique which is suitable for use with any material. A microcomputer is used to analyse interference fringe patterns in order to determine length changes to an accuracy of 3 nm. Test results are presented for the linear thermal expansion coefficients of fused silica and copper obtained using the apparatus.