Optical spectroscopy measurements of shock waves driven by intense z-pinch radiation

Z-pinches, created using the Z accelerator, generate ∼220 TW, 1.7 MJ radiation pulses that can heat large (∼103 cm) hohlraums to 100–150 eV temperatures for times of order 10 ns. We are performing experiments exploiting this intense radiation to drive shock waves for equation of state studies. The shock pressures are typically 1–10 Mbar with 10 ns duration in 6-mm-diameter samples. We demonstrate the ability to perform optical spectroscopy measurements on shocked samples located in close proximity to the z-pinch. These experiments are particularly well suited to optical spectroscopy because of the relatively large sample size and long duration. The optical emission is collected using fiber optics and recorded with a streaked spectrograph. Other diagnostics include VISAR and active shock breakout measurements of the shocked sample and a suite of diagnostics that characterize the radiation drive. Our near term goal is to use the spectral emission to obtain the temperature of the shocked material. Longer term objectives include the examination of deviations of the spectrum from blackbody, line emission from lower density regions, determination of kinetic processes in molecular systems, evaluation of phase transitions such as the onset of metallization in transparent materials, and characterization of the plasma formed when the shock exits the rear surface. An initial set of data illustrating both the potential and the challenge of these measurements is described.