Characterization of Sapphire for Optical Pyrometry in Shock Experiments.

Pyrometry measurements on shock-heated metals are often performed through a transparent anvil. Sapphire is an interesting anvil, but is also known to emit light when shocked above its Hugoniot Elastic Limit (HEL). To study its optical response, we have carried out experiments in the 15–37 GPa pressure range on c-cut sapphire in contact with a metallic sample (tin or bismuth) or a lithium fluoride window. Even though a significant amount of light is emitted by sapphire, we notice that the signal rise is directly related to the volume of sapphire under shock-loading. Consequently, the window emission can be subtracted to infer the thermal radiation originating from the metal under study. A theoretical calculation of the expected pyrometer signals supports that point of view. These results give evidence that sapphire, despite its shock-induced optical emission above the HEL, can be used as a transparent anvil for quantitative pyrometry measurements at medium and high shock pressures. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]