Progress towards a more predictive model for hohlraum radiation drive and symmetry.
Progress towards a more predictive model for hohlraum radiation drive and symmetry.
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DOI：
10.1063/1.4982693
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发表时间：
2017-05
影响因子：
2.2
通讯作者：
Turnbull DP
中科院分区：
文献类型：
--
作者：
Jones OS;Suter LJ;Scott HA;Barrios MA;Farmer WA;Hansen SB;Liedahl DA;Mauche CW;Moore AS;Rosen MD;Salmonson JD;Strozzi DJ;Thomas CA;Turnbull DP
几年来，我们一直在计算激光加热的金黑腔中的辐射驱动，使用通量限制的热传输，限制器为0.15，表列的局部热力学平衡金不透明度值，以及不处于局部热力学平衡（NLTE）金发射率的近似模型（DCA_2010）。这个模型已经成功地预测了真空黑腔中的辐射驱动，但对于用于驱动胶囊内爆的充气黑腔，该模型始终预测太多的驱动和胶囊爆炸时间早于测量。在这项工作中，我们引入了一个新的模型，使计算的爆炸时间与测量的爆炸时间更好地吻合。新模型采用（1）在空间、能量和时间上完全收敛的数值网格，（2）修改后的近似NLTE模型，包括更多的物理特性，并与更详细的离线发射率模型更好地一致，以及（3）降低的通量限制值为0.03。我们应用这个模型的气体填充的黑腔实验，使用高密度碳和塑料烧蚀胶囊，黑腔他填充气体密度范围从0.06到1.6毫克/立方厘米和黑腔直径为5.75或6.72毫米。新的模型预测爆炸时间在±100 ps的大多数实验与低到中等填充密度（高达0.85毫克/立方厘米）。该模型预测等离子体中的温度比旧模型更高，并且还预测在更高的气体填充密度下，大量的内束激光能量通过相对的激光入口孔逸出黑腔。
For several years, we have been calculating the radiation drive in laser-heated gold hohlraums using flux-limited heat transport with a limiter of 0.15, tabulated values of local thermodynamic equilibrium gold opacity, and an approximate model for not in a local thermodynamic equilibrium (NLTE) gold emissivity (DCA_2010). This model has been successful in predicting the radiation drive in vacuum hohlraums, but for gas-filled hohlraums used to drive capsule implosions, the model consistently predicts too much drive and capsule bang times earlier than measured. In this work, we introduce a new model that brings the calculated bang time into better agreement with the measured bang time. The new model employs (1) a numerical grid that is fully converged in space, energy, and time, (2) a modified approximate NLTE model that includes more physics and is in better agreement with more detailed offline emissivity models, and (3) a reduced flux limiter value of 0.03. We applied this model to gas-filled hohlraum experiments using high density carbon and plastic ablator capsules that had hohlraum He fill gas densities ranging from 0.06 to 1.6 mg/cc and hohlraum diameters of 5.75 or 6.72 mm. The new model predicts bang times to within ±100 ps for most experiments with low to intermediate fill densities (up to 0.85 mg/cc). This model predicts higher temperatures in the plasma than the old model and also predicts that at higher gas fill densities, a significant amount of inner beam laser energy escapes the hohlraum through the opposite laser entrance hole.