Simultaneous Measurements of Thermal Relaxation Times and Thermal Diffusivity at Low Temperature by Transient Laser-Heating Technique

瞬态测温不仅为热物性的高速测量提供了途径，而且为热传导中的一些新现象提供了途径。在低温范围内，利用波长为632.8 nm的激光椭偏仪测定了光学反射率的温度依赖性。利用连续波探测技术，研制了一套瞬态反射测量系统，用于测量10 ~ 300 K范围内的瞬态温度响应。用激光脉冲辐照加热箔试样的前表面。对连续波激光器后表面的反射率进行了原位测量，利用反射率与温度的关系推导出了薄膜的瞬态温度响应。通过对广义热传导问题的逆分析，给出了一种估计热扩散系数和松弛参数的一般方法。该方法通过将理论公式拟合到温升实验数据中来推导热物性。以不锈钢箔为样品，通过与理论温度响应和文献中的热扩散系数数据进行比较，验证了计算结果的准确性。本文所做的工作为今后研究非傅立叶现象提供了理论和实验准备。

The transient temperature measurement gives approaches to not only high-speed measurement of thermophysical properties but also some new phenomena in heat conduction. In this work, the temperature dependency of optical reflectivity is determined by a laser ellipsometer at a wavelength of 632.8 nm in the range of low temperature. A transient reflectance measurement system is developed for measuring the transient temperature responses in range of 10 K to 300 K by using the continuous wave probing technique. The front surface of a foil specimen is heated by a laser-pulse irradiation. In situ measurement of the reflectivity of a continuous wave laser at the rear surface is conducted, the transient temperature response of film is then deduced using the temperature dependence of reflectivity. A general method for estimating the thermal diffusivity and relaxation parameters is given by the inverse analysis of generalized heat conduction problem. The method is employed to deduce thermophysical properties by fitting theoretical formulae to the experimental data of temperature rise. The stainless steel foils are chosen as samples and the accuracy is examined by comparing with the theoretical temperature responses and the thermal diffusivity data from the literatures. What done in this work gives the theoretical and experimental preparations to study the non-Fourier phenomena in the future.