We report on numerical simulations of laser-driven convergent plasma fusion targets. These “inverted corona” fusion targets are useful for the study of counter-streaming and converging rarefied plasma flows, and previous experiments have demonstrated their potential as neutron sources. The scheme consists of a fuel layer lined along the interior surface of a hollow plastic shell that is laser-ablated and expands inward towards the target center. The plasma streams generated in these targets are initially nearly collisionless as they converge, leading to wide interaction length scales and long interaction time scales as the jets interpenetrate. Such kinetic effects impact mixing of constituent ions - a phenomenon not properly captured by single-fluid hydrodynamic simulations. Here we conduct numerical simulations using two different methods: (1) single-fluid simulations in HYDRA, and (2) kinetic-ion, fluid-electron hybrid particle-in-cell (PIC) simulations in the code Chicago. It is shown that the initially nearly collisionless plasma fronts interpenetrate deeply and lead to broader interaction regions in space and time resulting in significant beam-beam fusion. The two approaches make different, testable predictions for the effect of fuel-layer thickness on neutron yield.

我们报告了激光驱动的会聚等离子体融合目标的数值模拟。这些“反向电晕”聚变靶可用于研究逆流和会聚稀疏等离子体流，并且先前的实验证明了它们作为中子源的潜力。该方案由沿着中空塑料壳内表面排列的燃料层组成，该燃料层被激光烧蚀并向目标中心向内扩展。在这些目标中生成的等离子流在收敛时最初几乎是无碰撞的，从而导致射流互穿时相互作用长度范围宽，相互作用时间范围长。这种动力学效应会影响组成离子的混合-单流体流体动力学模拟无法正确捕获这一现象。在这里，我们使用两种不同的方法进行数值模拟：（1）HYDRA中的单流体模拟，以及（2）代码芝加哥中的动力学离子，流体电子混合细胞内粒子（PIC）模拟。结果表明，最初几乎无碰撞的等离子锋面会相互渗透，并在空间和时间上导致更宽的相互作用区域，从而导致明显的束流融合。两种方法对燃料层厚度对中子产率的影响做出了不同的，可检验的预测。