The conversion of laser light into soft x rays by irradiation of a high-Z material is theoretically investigated for open, planar geometry. The material may be subdivided into a hot, low-density conversion layer, optically thin for the x rays, and a dense, optically thick reemission zone. The two layers are coupled through radiation only. Dimensional analysis yields asymptotic expressions for the x-ray conversion efficiency and the reemission coefficient and hence for the total converted flux from the target.

The propagation of a radiation heat wave through a thin foil of solid gold was investigated experimentally. The wave is driven by the intense thermal radiation in 1-3-mm-diam gold cavities heated by an intense laser pulse (duration 0.8-0.9 ns, wavelength 0.35 ttm) to temperatures of more than 200 eV. Evidence of the propagating wave was obtained from the delayed onset of intense thermal emission from the outer side of the foil. The results agree with theoretical predictions for a self-similar ablative heat wave and with numerical simulations.

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The propagation of a radiation heat wave through a thin foil of solid gold was investigated experimentally. The wave is driven by the intense thermal radiation in 1 -3-mm-diam gold cavities heated by an intense laser pulse (duration 0.8 -0.9 ns, wavelength 0.35 pm) to temperatures ranging from 80 to 240 eV.Evidence of the propagating wave was obtained from the delayed onset of thermal emission from the outer side of the foil. A detailed comparison of the results with the self-similar solution for the ablative heat wave and with numerical simulations is presented.PACS number(s): 52.50. Jm, 44.40.+a, 47.70.Mc

Thermal x-ray confinement in a laser-heated gold cavity was investigated. Intense blue laser light (wavelength 351 nm, energy 5 kJ, duration 0.9 ns) irradiated the inner surface of (1 -3)-mm-diam gold shells at average intensities up to 2X10' W/cm to generate the source x ray for the confinement. A maximum brightness temperature of 240 eV and a quality factor of confinement of N =5.3 (corresponding to a reemission coefficient of r =0.84) have been achieved. Experimental results are in satisfactory agreement with theoretical predictions based on the self-similar ablative heat wave driven by radiation and with numerical simulations.PACS number(s): 32.30. Rj, 44.40.+a, 52.25.Nr, 52.50.Jm