Simulating x-ray Thomson scattering signals from high-density, millimetre-scale plasmas at the National Ignition Facility
Simulating x-ray Thomson scattering signals from high-density, millimetre-scale plasmas at the National Ignition Facility
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DOI：
10.1063/1.4893146
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发表时间：
2014-08-01
影响因子：
2.2
通讯作者：
Doeppner, T.
中科院分区：
文献类型：
--
作者：
Chapman, D. A.;Kraus, D.;Doeppner, T.
我们已经开发了一个模型，用于分析在国家点火设施中以球形会聚几何形状的超高压内爆产生的高密度毫米级非均匀等离子体的x射线汤姆森散射数据。散射信号的密度加权以及入射和散射x射线在整个目标中的衰减都包括在辐射流体动力学模拟提供的密度、不透明度、电离状态和温度的径向分布中。这些模拟结果表明，散射信号被强烈地向冲击等离子体的主体和靠近烧蚀锋面的费米简并物质倾斜。我们表明，散射信号可以很好地表示这种高度不均匀的体等离子体的温度，并且可以使用简单的0D计算的典型数据分析技术确定精度约为15%。另一方面，整体碳的平均电离被低估了。我们认为这种差异是由于来自目标不同区域的散射轮廓的卷积。随后，我们讨论了对当前平台的修改，以最大限度地减少不均匀性和不透明性的影响，并使探测条件更倾向于压缩核心。
We have developed a model for analysing x-ray Thomson scattering data from high-density, millimetre-scale inhomogeneous plasmas created during ultra-high pressure implosions at the National Ignition Facility in a spherically convergent geometry. The density weighting of the scattered signal and attenuation of the incident and scattered x-rays throughout the target are included using radial profiles of the density, opacity, ionization state, and temperature provided by radiation-hydrodynamics simulations. These simulations show that the scattered signal is strongly weighted toward the bulk of the shocked plasma and the Fermi degenerate material near the ablation front. We show that the scattered signal provides a good representation of the temperature of this highly nonuniform bulk plasma and can be determined to an accuracy of ca. 15% using typical data analysis techniques with simple 0D calculations. On the other hand, the mean ionization of the carbon in the bulk is underestimated. We suggest that this discrepancy is due to the convolution of scattering profiles from different regions of the target. Subsequently, we discuss modifications to the current platform to minimise the impact of inhomogeneities, as well as opacity, and also to enable probing of conditions more strongly weighted toward the compressed core.