An absolute interferometric dilatometer

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Abstract
The dimensional changes produced in materials by temperature variations are generally very small, so that sensitive measuring techniques must be used to observe them. The interferometer developed at NPL for thermal expansion measurement exploits the high resolution and accuracy of laser interferometry in a dilatometer design which places a minimum of restrictions on the shapes and dimensions of specimens which can be measured. The presentation of thermal expansion data is discussed and relationships between the relevant parameters are derived. Many different materials have been investigated and some results of interest are included here.