Free-surface temperature measurement of shock-loaded tin using ultrafast infrared pyrometry

摘要

Abstract: The main problem regarding free surface temperature measurement by infrared pyrometry is the lack of emissivity data of shocked materials. Moreover, the short rise time in an hydrodynamic experiment requires particular detectors and experimental measurement technique. This paper describes a three channel pyrometer adapted to the study of shocked tin sample melted in release. The radiative infrared emission is collected by ZnSe lens and carried from the firing chamber to the pyrometer by fluoride glass optical fiber. In order to deduce the temperature from the electrical signals amplified before recording on a numerical oscilloscope, we use different narrow filters associated with a previous static calibration of the detectors by means of a continuously heated black body. The spectral integration of Planck's formula and the comparison between the static calibration with the black body and the dynamic signals give, for each experiment, three temperature-emissivity couples in agreement with Planck's theory. The originality of this measurement technique is the use of a 15 meter infrared optical triple core fiber for transporting the radiation from the target to the detectors, which simultaneously permits the measurement of three temperature-emissivity couples in the case of very small and hermetic experimental set-up. The main characteristics of this pyrometer are: a rise time of about 20 nanoseconds; an analysis area with a diameter smaller than 5 millimeters; continuous free surface temperature measurement during more than 5 microseconds; and the study of the wavelengths between 2 and 5 micrometers. Experiments have been achieved with optical polished tin samples. The abacus voltages, temperature, and emissivity versus time for a 45 GPa shock pressure is discussed.!10