Shock Wave Overtake Measurements on Cesium Iodide

Abstract

The present shock wave experiments on cesium iodide were carried out as a complement to the shock wave optical pyrometry measurements on cesium iodide by Radousky, et al.¹ Those experiments gave temperatures along the Hugoniot from 0.25 Mbar to 0.91 Mbar, and suggested that melting occurred at approximately 0.32 Mbar and 3700 K. One reason for the interest in melting in CsI is the suggestion by Ross and Rogers² that under these conditions the coordination number for liquid CsI will have changed from the normal 6 to 12, the value for a rare gas atom. The luminosity of the shock front for CsI makes it an ideal material for which to measure directly sound velocities along the Hugoniot using shock wave overtake methods.³ In these measurements, the occurrence of melting along the Hugoniot is marked by a discontinuous decrease in the measured sound velocity.^4,5 In addition, CsI is isoelectronic with xenon, and is expected to begin to show metallic behavior along the Hugoniot near 0.9 Mbar.⁶ The directly-determined sound velocities and corresponding elastic moduli would be expected to be more sensitive to this transition than either Hugoniot equation of state or optical pyrometry experiments. The following gives a brief description of the present experiments and results. A more complete discussion of the results will be published elsewhere.⁷

Work done at Las Alamos National Laboratory and sponsored by the U. S. Department of Energy.

Operated by Iowa State University for the U. S. Department of Energy under Contract No. W-7405-Eng-82. This work was supported in part by the Director for Energy Research, Office of Basic Energy Sciences.