MEASUREMENT OF THE THERMAL EXPANSION COEFFICIENT BY DIODE LASERS

摘要

We present an apparatus that allows to measure the thermal expansion coefficient (TEC) of solid samples in the range from room temperature up to temperatures as high as 450℃, up to date. The dilatometer that measures the length changes of the sample can be roughly described to consist of two diode lasers, two photodiodes, whose sensitive surface area is divided in two sectors, and of an acquisition system of the photodiodes outputs, which permits the signal analysis through a PC. The temperature is measured by a thermocouple. The sensitivity in the length change measurement was determined about one hundredth of micrometer by measuring the photodiode output versus calibrated displacements of the order of the micron, and that in the detection of the temperature close to five hundredth of Celsius degree (by using a chromel-alumel thermocouple and a microvoltmeter). The experimental results on the TEC of a fused silica sample are also presented.