Low-temperature thermal expansion of beryllium as an optical material

Abstract

A study has been completed on hot isostatic pressed beryllium to determine its suitability for mirrors to be used in space telescopes.1 This study was performed for the Perkin-Elmer Corp, on small cubic specimens cut from specified locations in various shaped large blanks of the material. The coefficients of thermal expansion for the samples were measured along various orthogonal directions to determine their isotropy in the temperature range from 60 to 310 K. Similar measurements were made on samples from various locations to determine their homogeneity. Graphs comparing the expansivity of beryllium against other optical materials2 are presented to illustrate the suitability of this form of beryllium as a mechanical support for optical elements.