Problems of shock temperature measurements for metals by using optical radiometry method

Abstract

Several problems encountered in shock temperature measurements for metals using optical radiometry were discussed in detail. The influences of the driver/film gap upon the observed interface temperature history were formulated analytically, and the temperature relaxation behaviors at the film/window interface were also characterized. We found that the energy deposition at the driver/film gap would influence to varied degrees the film/window interface temperature profile unless the film deposited on the window can be regarded to have an infinite thickness. Modeling calculations showed that at shock pressures of a few megabars, the observed interface temperature of iron would be at least 300–600 K higher, relative to the prediction from the Grover model, provided that the gap and film were both 1 ～ 2 pm thick. Additionally, a metal-plate sample was used to measure a reliable shock temperature based on one-dimensional heat conduction model for the plate-sample(driver)/ pm-gap/window setup we proposed. Preliminary measured results for a meteoritic iron sample (kamacite, with Fe 93.65 wt.% and Ni 6.35 wt.%) using a disc sample showed that this method was practical and effective. Finally, the “heat-resistance model” proposed by Tang et al., and the experimental measurement of the heat conductivity for a transparent window (sapphire or LiF crystal) at megabar shock pressures were discussed and commented on as well.