Long-term dimensional stability and longitudinal uniformity of line scales made of glass ceramics

Abstract

Line scales are commonly used as a working standard of length for the calibration of optical measuring instruments such as profile projectors, measuring microscopes and video measuring systems. For high-precision calibration, line scales with low thermal expansion are commonly used. Glass ceramics have a very low coefficient of thermal expansion (CTE) and are widely used for precision line scales. From a previous study, it is known that glass ceramics decrease in length from the time of production or heat treatment. The line scale measurement method can evaluate more than one section of the line scale and is capable of the evaluation of the longitudinal uniformity of the secular change of glass ceramics. In this paper, an arithmetic model of the secular change of a line scale and its longitudinal uniformity is proposed. Six line scales made of Zerodur®, Clearceram® and synthetic quartz were manufactured at the same time. The dimensional changes of the six line scales were experimentally evaluated over 2 years using a line scale calibration system.

Spontaneous crystallization noise in mirrors of gravitational wave detectors

“…In this way some contraction of fused silica samples in time should be observed if devitrification takes place. This effect of contraction is indeed known for glasses and its rate for different materials was measured [13][14][15]. From the other hand, each event of local crystallization is a discrete event causing small perturbations.…”

“…As one can see from the Table I [13][14][15]. From the other hand, each event of local crystallization is a discrete event causing small perturbations.…”

Absolute refractometry of dry gas to ±3 parts in 10^9

“…The FP cavities (both spacer and end mirrors) were made of ultralow expansion (ULE) glass [14], and the end mirrors were optically contacted (Van der Waals bond) to the spacer. The salient property of ULE that makes it desirable for absolute refractometers is its long-term dimensional stability [15] compared to other low thermal expansion materials [12,16]. However, ULE has the disadvantage that it absorbs helium, as will be discussed shortly.…”

Characterization of the long-term dimensional stability of a NEXCERA block using the optical resonator technique

“…For ULE, values of the fractional length drift rate L −1 d∆L/dt ≈ −2.5 × 10 −8 yr −1 have been reported [15], as well as significantly lower ones, −0.4 × 10 −8 yr −1 [12]. Zerodur has a relatively large dimensional instability, −0.1 × 10 −6 to −0.2 × 10 −6 yr −1 , [13,15], making it less suitable for applications requiring extreme long-term stability.…”