Abstract：The thermal expansion measurements with NIM’s precision interferometer are described.The measurements are based on the observation of the length change of the material samples as a function of a temperature using laser interferometry. The interferometer and the material sample up to 1m are situated in a tight enclosure which temperature is controlled by a water circulation within a temperature range from 5 ℃ to 40 ℃.A heat-balanced interference mirror was designed.A high precision temperature measuring system is used for measuring the temperature of the material sample and the air.The accurate determination of the refractive index of air and the real-time compensation of zero error are accomplished. Using an 500 mm gauge block, thermal expansion coefficient is measured with a relative deviation of less than 0.2%, and it was compared with those of Physikalisch-Technische Bundesanstalt (PTB) of Germany. The coefficient of thermal expansion can be obtained with a uncertainty less than 3×10-8K-1.
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2012, Vol. 33 
