A sharp density increase (referred to as density incrustation) of the Au plasmas in the radiative cooling process of high-Z Au plasmas confined by low-Z CH plasmas is found through the radiative hydrodynamic simulations. The temperature of Au plasmas changes obviously in the cooling layer while the pressure remains constant. Consequently, the Au plasmas in the cooling layer are compressed, and the density incrustation is formed. It is also shown that when the high-Z plasma opacity decreases or the low-Z plasma opacity increases, the peak density of the density incrustation becomes lower and the thickness of the density incrustation becomes wider. This phenomenon is crucial to the Rayleigh–Taylor instability at the interface of high-Z and low-Z plasmas, since the density variation of Au plasmas has a considerable influence on the Atwood number of the interface.

Hydrodynamic processes of radiation-ablated high-Z plasmas have great influence on the x-ray radiation transport both in a high-Z tube with low-Z foam filling and in a low-Z filling indirect drive cavity. Using the intense x-ray radiation to heat a low-Z foam-tamped high-Z gold plate from a half cavity, the hydrodynamic moving process of the x-ray-ablated gold plasma has been studied by an imaging method with Ti He-α line emission as the backlighter source. The hydrodynamic trajectory of the x-ray-heated gold plasma was obtained and the average trajectory velocity of (36.5±1.2) km/s was derived. The experimental trajectory was compared with the simulations using the one-dimensional (1D) RDMG [P. Gu et al., Sci. China, Ser. G 48, 345 (2005)] and two-dimensional (2D) LARED-R [K. Lan et al., Laser Part. Beams 23, 275 (2005)] codes separately. It is shown that the 2D LARED-R code simulated the measured plasma trajectory much better than the 1D RDMG code due to the fact that the lateral x-ray radiation loss was taken into account in the 2D LARED-R but not in the 1D RDMG simulations.

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The energy leaking through a slot in the hohlraum filled with low-<i>Z</i> foams is a typical dynamic problem of the ablated high-<i>Z</i> plasmas. In this paper, we develop a simplified one-dimensional model to study the expansion-reverse process of the ablated Au plasmas, which corresponds to the closing-reopening process of a slot. Our work shows that its physical mechanism is the ablation pressure competing with radiation pressure difference and the material pressure of low-<i>Z</i> foams. The analytical formulas for the reverse time and reverse distance of the Au plasma are deduced, respectively, indicating that the cubic value for each of both peak temperatures is proportional to the density of the low-<i>Z</i> foams. The main conclusions of analytic theory are verified by numerical simulation through using the modified radiation-hydrodynamic program MULTI. It is shown that the power exponents of scaling law in high-<i>Z</i> plasma ablation keep unchanged in a wide range of density of low-<i>Z</i> foams. The range of validity of the model is discussed.

K-shell absorption spectroscopy of radiatively heated Al sample is reported. The experiment was conducted on Shenguang-Ⅱ Laser facility. Eight main beams of the facitliy are injected into a conical gold cavity to produce high-temperature X-ray heating source. This X-ray source is then used to irradiate an Al foil located in the center of the cavity, and heat the foil to temperature of tens of electronvolt. After a time delay, a ninth short-pulsed laser beam is focused on a gold disk to generated an X-ray point-backlighter. By measuring the spectra both directly from backlighter and attenuated by the heated sample in the wavelength range of 075—085nm, the K-shell absorption spectrum of Al is obtained. By fitting the experimental spectrum with theoretical calculation, electron temperature of the heated sample is determined.