Analysis of temperature measurement at material/LiF interface under moderate shock wave compression

Abstract

In the field of dynamic high-pressure physics of condensed materials, the accurate knowl- edge of the thermodynamic state of a material is fundamental to understand its dynamic behaviour under stress. The equation of state of materials is verified in terms of pressure, density and internal energy thanks to the measurements of pressure and velocity under shock wave compression with a satisfying precision. The theoretical temperature evaluated from EOS remains discussed. So; its ac- curate measurement is of great interest, in particular at low temperature. However, in this range, measurements appear more difficult to perform. Because of this, a high-speed infrared three-wave- length pyrometer has been modified at CEG to perform measurements at very low temperature (<500 K). Besides, an emissive layer has been designed to increase the emissivity of the shocked surface. To reduce the uncertainty of the temperature measurement, it appears necessary to limit its emissivity to a 0.9-1 range. 1. EXPERIMENTAL SETUP The technique to approach as close as possible the shock temperature is to record the spectral radiance emitted from the surface of the target through a window with a pyrometer. It is well- known technique above 900 K (1,2), but this technique is difficult to adapt for low radiance temperature measurements (<500 K) while guarantying a good precision. The aim of this work is to adapt a pyrometer to perform low radiance temperature measurements on plate impact experiments and to reduce the interface temperature measurement uncertainties by using an emissive layer at the interface.