Abstract
The measurement of temperature of a material at shock compression is one of the way to investigate the thermodynamic properties of the material and other phenomena induced by shock compression, which are sometimes difficult to be observed by conventional Hugonit experiments. Optical measurement is the most available to estimate the shock temperature. There are, however, a few problems, because the material must be transparent for this measurement and/or the shock compressed state is not homogeneous from mechanical, optical and thermal views. To solve these problems, it is necessary to observe not only the time profile of radiance but also the spectrum of it. Fused silica is one of the materials well investigated by such method.
The absorption coefficient of shock compressed material is estimated from the radiance profile, and increases with pressure. In low pressure region, it is difficult to estimate the shock temperature, because heterogeneous emissions are comparable to homogeneous thermal radiation. In high pressure region, the radiance spectrum has not any anomalous structures, and the brightness can be related to the shock temperature.
The radiance profile indicates a characteristic property of shock compression. The temperature is the lower in the layer the closer to the shock front. It is the result of relaxation process from heterogeneous strain to heat behind the shock front.
