Experimental studies on the opacity of dense aluminum compressed by a laser-driven shock waves

The high-precise opacity of the dense plasma has important applications in the design and simulation of fusion research, and in plasma diagnostics. Base on the novel technique of point-projection backlighting, a broadband high-resolution elliptical crystal X-ray spectrometer, which is used to measure simultaneously the self-emission spectrum, the backlighting source spectrum, and the transmission spectrum in one shot, is designed on the Shengguang-II laser facility. The process of the colliding-shock-compressed sample by laser-driven shock waves is also investigated using a one-dimensional radiation hydrodynamics code MULTI. In the measurement, the dense plasma, produced in aluminum by colliding shocks driven by laser beams, reaches a peak density several times that of a solid, and the short backlighting from the 3d-4f transition bands of ytterbium is used as an absorption source for time- and space-resolving diagnostics. Several experimental results are obtained, they are the X-ray source spectrum, the transmission spectrum, and the self-emission spectrum of the dense Al sample in one shot obtained by using the point-projection method, as well as X-ray-absorption fine-structure spectra, and the changes in the K-shell photo-absorption edge of aluminum as it was compressed by a laser-driven shock waves. The transmissivity distribution and red- shift around 80 m (with respect to the cold value of 1.56 keV) of the dense aluminum are also obtained. The data obtained are further analysed. As a result, a new theoretical model is developed.