Initial Results From a Simultaneous Pyrometry and Reflectivity Diagnostic

Pyrometry is an established technique used in high strain rate experiments (such as plate impact experiments) whereby the temperature of a sample is determined from the measurement of collected thermal radiation. By applying Planck's Law, radiometry data can be used to determine temperature. A significant source of uncertainty in applying pyrometry to high strain rate experiments is due to possible changes in emissivity after a sample has been shocked; thus it is desirable to determine emissivity during the experiment. Kirchhoff's Law, which states emissivity is the complement of reflectivity, can be applied to determine emissivity in high strain rate experiments. Ideally the sample's reflectivity would be measured at the same wavelength and on the same experiment as the pyrometry measurement. A diagnostic has been developed which produces a modulated reflectivity signal that is insensitive to tilt and surface finish. Following characterisation of the system in the laboratory, dynamic tests were conducted. During the dynamic tests, the reflectivity signal was multiplexed onto the radiance signal allowing simultaneous measurement of radiance and reflectivity. A description of the diagnostic, results from laboratory testing and results and analysis from dynamic experiments are presented. (C) British Crown owned copyright 2017/AWE.