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PLASMA-PHYSICS-04 Optimization of the hohlraum wall composition

By E. Yu. Arapova, M. A. Barinov, M. A. Vronskii, G. V. Dolgoleva and V. F. Yermolovich

Abstract

Experimental investigations on the conversion of Nd-laser radiation (λ = 532 nm, intensity 10 13 W/cm 2) into X-rays by irradiating gold/copper alloys have shown a dependence on the atomic percentage of gold in the alloys [1, 2]. The X-ray yield in the photon energy region up to 1 keV reaches the maximum when the alloy contains 43 % of gold. For harder X-rays above 1 keV the yield decreases drastically with a higher percentage of gold in the alloy. Adding 12 % of gold into the copper of the originally investigated alloy results in a decrease by a factor of 2.1 for X-ray’s above 1 keV. The one-dimensional code SND [3] is developed for calculations of two temperature gas dynamics of plasma expansion and includes the radiation transport in a diffusion approximation. The wavelength dependent radiation diffusion in materials was used to determine the conversion of laser radiation into X-rays in AuCu alloys by variation of the gold content. The needed spectral opacities were obtained using the THERMOS code [4], which calculates spectral absorption ratios on the basis of the average atom model in the modified Hartree–Fock-Slater approximation. Fig.1 shows the curves calculated for the X-ray flux (energies up to 1 keV) emitted from a Au0.43Cu0.57- alloy at a laser intensity of 10 13 W/cm 2. For a part of the X-ray spectrum the maximum yield of the radiation from the Au/Cu-alloy is higher than that from laser irradiated pure gold- or copper-targets. For example the X-ray´s yield from the Au0.43Cu0.57- alloy at 0.15 keV, 0.3 keV and between 0.7 – 1 keV is higher than the yield from the pure gold or copper, irradiated with the same laser parameters. For the X-ray energies higher than 1 keV a significant decrease in the X-ray yield is observed for alloys containing more gold, see Fig. 2. Figure 2: The calculated ratios of fluxes for the AuxCu1-xand for the pure Au in the photon energy range of 1.15-1.6 keV: S ( Au Cu) / S ( Au) [1.15, 1.6] keV x 1 − x [1.15

Year: 2012
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