Properties of Low-Expansion Materials for Hydrogen Maser Cavities

Abstract

We have measured thermal and mechanical properties of four low-expansion materials that are candidates for use in hydrogen maser resonant cavities: Cer-Vit@ C-l01 and C-126, ULE', and Zerodur@. Thermal expansivities were measured at room temperature and after heating the samples to 3OO0C and to 700°C. The approximate expansivities, (1/L) (dL/dT) , in units of 10-8 OC-1, are: Cer-Vit C126, -40; Cer-Vit C101, -13; Zerodur, -12 to -6; and ULE, +5. Zerodur's expansivity decreased in magnitude by 50% after heating to 7OO0C, while the expansivities of ULE and Cl01 remained substantially unchanged.