THE INFLUENCE OF LASER BEAMS POWER IMBALANCE ON SYMMETRY OF ABSORBED ENERGY IN THE CORONA OF DIRECT-DRIVEN TARGETS
I. A. Khimich, V. A. Lykov
VANT. Ser.: Mat. Mod. Fiz. Proc 2017. Вып.2. С. 42-52.
The absorption of laser energy has been simulated in the geometrical optics approximation with regard to refraction in an isothermal corona and with the exponential law of the radial electron density distribution. Two target illumination configurations are considered: 1) 6 × 8 clusters around the directions passing through the centers of cube faces; 2) 8 × 6 clusters, which axes of symmetry pass through cube corners. According to simulation results, the mean-root-square deviation of the absorbed laser energy in a solid angle under optimal irradiation conditions is Δ ≈ 0,73% and 6 × 8 и Δ ≈ 0,52% for the 6 × 8 and 8 × 6 configurations, respectively. The absorbed energy expansions in spherical harmonics demonstrate that for the chosen target illumination configurations the leading ones are harmonics 4 and 8. The power imbalance of laser beams taken into account in simulations beams leads to degradation of symmetry in the absorbed energy distribution and occurrence of lower harmonics. The mean-root-square deviation of the absorbed laser energy does not exceed 1% , with the standard deviation in the laser beams power not exceeding 3% and 5% for the 6 × 8 and 8 × 6 illumination configurations, respectively. Keywords: direct-driven targets, a megajoule laser facility, power imbalance of laser beams, non-uniformity of absorbed energy.
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