Radiation temperatures of soda-lime glass in its shock-compressed liquid state

A radiation pyrometer in conjunction with a two-stage light gas gun has been used to measure shock temperatures of soda-lime glass in the pressure range 54-109 GPa. This pyrometer consists of two parts, i.e., an optical multichannel analyzer which measures the radiation spectrum over the visible range (similar to 450 nm window) and a four-channel photomultiplier tube system which records the time-varying behavior of shock temperatures. The measured radiation spectra are compared with the Planck function to estimate the shock temperatures and emissivities. Obtained spectra are well fit by the Planck function with moderate emissivities, indicating that relatively homogeneous thermal radiation is the main component of radiation. Obtained shock temperatures range from 2800 (100) to 5700 (300) K and they seem to represent shock temperatures of liquefied soda-lime glass (melt). The Hugoniot is well described by a linear relation, u(s) = 0.14(21) + 1.92(5)u(p) km/s. It is deduced that the radiation from liquids under shock compression, in contrast to the radiation from solids under shock compression, is more thermal and fits the Planck function well, even at lower temperatures. This is because the radiation spectrum of solids under compression often shows nonthermal radiation due to heterogeneous deformation, while the radiation spectrum of liquids under compression could not have such a nonthermal component. (C) 1998 American Institute of Physics. [S0021-8979(98)08103-1].