激光等离子体能量角分布及吸收定标律

LASER PLASMA ENERGY ANGULAR DISTRIBUTION AND ABSORPTION SCALING LAWS

主要研究激光平面靶等离子体发射能量角分布及吸收定标律。实验利用高斯型1.06μm激光脉冲,其能量为2～50J,脉冲宽度为0.3～2.2ns,靶面平均辐照强度为1.8×1013～1.1x10^(15)W/cm^2,光束以25°角入射。实验采用了Au、Ag、Ti、Al和C_8H_8等厚靶。用等离子体卡计测量靶面吸收的激光能量。用指数函数拟合实验数据,给出了吸收效率分别作为激光强度、脉冲宽度和靶材料原子序数的函数的定标关系式。这些关系式定性地与逆轫致吸收的理论关系式相一致。

Experiments to study the laser plasma angular distribution and the absorption scaling laws for planar targets are reported. Gaussian (0.3 to 2.2ns) 1.06μm laser pulse with energy from 2 to 50J at average laser intensity of 1.8×1013 to 1.1 × 1015W/cm2, were used to irradiate thick, Au, Ag, Ti, Al, and C8H8 targets. The absorption was measured with plasma calorimeters. The experimental data were fitted with exponential functions. Scaling relations of the absorption efficiencies as function of laser intensity, pulse duration, and target material atomic number were presented, respectively. The scaling relations of absorption efficiency are qualitatively consistent with theoretical relations of the inverse- bremsstrahlung absorption.