The coefficient of thermal expansion (CTE) and its spatial homogeneity from small to large formats is the most important property of ZERODUR. Since more than a decade SCHOTT has documented the excellent CTE homogeneity. It started with reviews of past astronomical telescope projects like the VLT, Keck and GTC mirror blanks and continued with dedicated evaluations of the production. In recent years, extensive CTE measurements on samples cut from randomly selected single ZERODUR parts in meter size and formats of arbitrary shape, large production boules and even 4 m sized blanks have demonstrated the excellent CTE homogeneity in production. The published homogeneity data shows single ppb/K peak to valley CTE variations on medium spatial scale of several cm down to small spatial scale of only a few mm mostly at the limit of the measurement reproducibility. This review paper summarizes the results also in respect to the increased CTE measurement accuracy over the last decade of ZERODUR production.

Date Published: 5 September 2017
PDF: 11 pages
Proc. SPIE 10401, Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems, 104010J (5 September 2017); doi: 10.1117/12.2272902

Published in SPIE Proceedings Vol. 10401:
Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems
Tony B. Hull; Dae Wook Kim; Pascal Hallibert, Editor(s)