Research On Radiation Behaviors And Temperatures Of Copper/sapphire Interface Under Shock Compression

In shock temperature measurements using optical radiometry technique, a transparent window (sapphire or LiF) deposited with a studied metal film was traditionally used to assure the ideal contact between metal and window, so that the interfacial temperature can be obtained from shock-loaded interface spectral radiance history. The shock temperature of metal is derived based on the quantitative relation among shock, release, and interfacial temperatures. However, there existed considerable scatter and uncertainty in the interfacial radiance measurements, and the transparent window (mostly in case of sapphire) was found to emit or absorb some radiation at lower pressures in recent research. So, some attentions should be paid on re-evaluating the spectral radiance from metal/window interface. In this article, the OFC copper sample was used as a representative metal to directly contact with sapphire to investigate the characteristic of interfacial radiation from bulk metal/window interface.The main results of this study are as follow:(1) To reduce the gap between copper and sapphire surface as small as possible, a uniform press was executed by means of compressed gaseous media. The initial interfacial condition was improved by increasing the pressure of compressed gas. Results showed that this prepressing technique is much better than mechanical one because the mechanical method could cause additional non-uniformity thickness of gap at contacted interface. The technique to prepare "nearly gapless" contact interface in our work was not reported elsewhere.(2) The spectral radiance history from copper/sapphire interface, with little influence of "high-temperature layer" , was firstly achieved under shock compression up to 100 GPa. Experimental results showed that the emission feature is sensitively dependent of the initial interface conditions. The measured radiation profile of shock-loaded interface was varied from wide and strong peak emission to narrow and weak when improving the interfacial contact situation.(3) A new method was brought forward to determine bulk meal/window interfacial temperature, namely, the interfacial temperature could be deduced from the forepart spectral radiance history. Since the real interfacial temperature can be directly obtained from the apparent interfacial temperature profile, the influence of light emission from optical window on temperature measurement can be avoided.