Temperature Measurement and Equation of State of Condensed Matter

Abstract

A dynamic method for creation and measurement of high pressures that has been developed in Russia and in the U.S. during the past 50 years allows study of condensed material properties over a wide range of densities and temperatures that cannot be reached by any other method [1–3]. A strong shock wave, having a velocity exceeding 10 km/s, heats the compressed substance up to several tens of thousands of degrees. If the substance is transparent in its initial state, e.g., an ionic crystal or noble gas, then measurement of the radiation passing from the shock-heated material through its uncompressed layer makes it possible to obtain unique information about its properties at the high pressure. Fundamental studies of the role of radiation in strong shock waves in gases were made by Zel’dovich and Raizer [1]. Model’ made the first measurements of the brightness temperature of a shock front in a gas [4]. Those pioneering studies showed the phenomenon of a sharp decrease of the brightness temperature from the shock front to the material behind the front. A large body of experimental data on the radiating properties of shock waves in dense gases is presented in [5]. At VNIIEF, Kormer was the absolute leader in experimental study of optical properties of shock compressed, transparent, condensed substances. He and Zel’dovich gathered around themselves a team of young enthusiasts who started investigations in the 1960s and 1970s [6]. This work is still unique.