EXPERIMENTAL INVESTIGATION OF RADIATIVE TRANSPORT IN X-RAY HEATED LOW-Z MATTER

Intense thermal x-rays with brightness temperatures in the range 50-10 0 eV have been generated in laser-irradiated high-Z targets such as pl ane thin converter foils or spherical micro-cavities. These x-ray sour ces were used to irradiate various absorber foils consisting of low-Z matter (Be, B, C and Al). The radiative heating of these materials has been studied by time-resolved spectroscopy at sub-keV photon energies . The radiative burnthrough occurring as a consequence of the transiti on from the cold solid state to an ionized gas has been observed. The measurements agree well with calculations of the radiation transport, for which electron impact line broadening was found to be essential. O f interest is also smoothing of the K-edge of Be and the L-edge of Al observed in the beginning of the heating when the foil is still dense and in a partially degenerate state. We also present first results on the reemission of carbon foils heated by x-rays generated in a gold mi cro-cavity.