Recent critical applications for ultralow expansion materials have required thermal expansion measurements with very high precision and accuracy. A Fizeau interferometer employing a helium–neon laser has given a precision of ±0.1 × 10−6 cm/cm. A second, more rapid method consists of a rod type vitreous silica dilatometer. A stirred water bath is used for specimen temperature control and a high output, linear variable differential transformer serves as the extensometer. Precision of this method is ±0.5 × 10−6 cm/cm. Calibration procedures and results for several low expansion materials are discussed.
© 1968 Optical Society of AmericaFull Article | PDF Article