Experimental investigation of diffusive supersonic radiation propagation in low density CH foam doped with Cu

Abstract

Eight beams of 0.35 mm laser with pulse duration of 1ns and 2 kJ of total energy enter into a hohlraum to create intense x-ray radiation on the Shenguang II laser facility. The plastic foam doped with 59 nanometers of Cu granule (C 6 H 12 Cu 0.394 ) at a low density of 50 mg/cm 3 is heated by x-ray radiation emitted from the hohlraum. The breakout time of the radiation wave is measured by a three chromatic streaked x-ray spectrometer (TCS) that consists of a set of three imaging pinholes and an array of three transmission gratings coupled with an x-ray streak camera (XSC). At one shot, the simultaneous measurements of the drive source and the radiation transport at two energies (210 eV, 840 eV) through the foam have been made for the first time. The experimental results indicate that the time delays vary with photon energies. The radiation at energy 210 eV propagates at a lower velocity. Using TGS, the transmitting spectrum was measured, and the lower limit of the optical depth, which is more than 1, was obtained. The Mach number of the radiation wave is about 4. The radiation transport in the foam doped with Cu is diffusively supersonic and the diffusion approximation begins to be applicable. The experimental data were compared with the simulation of two-dimensional radiation hydrodynamics code and they reasonably agree.PACS: 52.50.Jm, 52.25.Nr