INFRARED PRECISION PYROMETRIC ANALYSIS OF THE TEMPERATURE OF SHOCK-LOADED METALLIC MATERIALS IN THE RANGE 70-DEGREES-C-1000-DEGREES-C

The infrared pyrometer described in a previous paper /1/ has been improved to determine time-resolved surface temperatures of shocked polished metal plates. The actual measurement range is 70-1000-degrees-C, the response time is about 60 ns and the accuracy is remarkable: +/- 3%. To overcome the general lack of knowledge for the emissivity of a shocked free-surface, the emissivity of the sample material is increased up to an apparent emissivity of about 0.8 using an integrating reflective cavity which includes: 1) an optimized specular cylindrical reflector for light collection associated to a fluoride glass fiber with high transmittance in the 4-5-mu-m range and 2) a 3000 angstrom-thick layer of vacuum deposited ReSi2 on the metal plate. The emissivity of the shocked material is thereby restricted in the 0.8-1 range, which determine the accuracy of the measured temperature. This technique has been used to record the residual temperature of pure copper subjected to shock loading by plate impact experiments in the range 29-97 GPa.