Cylindrical foil liners, with foil thicknesses on the order of 400 nm, are often used in university-scale Z-pinch experiments (∼1 MA in 100 ns) to study physics relevant to inertial confinement fusion efforts on larger-scale facilities (e.g., the magnetized liner inertial fusion effort on the 25-MA Z facility at Sandia National Laboratories). The use of ultrathin foil liners typically requires a central support rod to maintain the structural integrity of the liner target assembly prior to implosion. The radius of this support rod sets a limit on the maximum convergence ratio achievable for the implosion. In recent experiments with a support rod and a pre-imposed axial magnetic field, helical instability structures in the imploding foil plasma were found to persist as the foil plasma stagnated on the rod and subsequently expanded away from the rod [Yager-Elorriaga et al., Phys. Plasmas 25(5), 056307 (2018)]. We have now used the 3D extended magnetohydrodynamics simulation code PERSEUS (which includes Hall physics) [C. E. Seyler and M. R. Martin, Phys. Plasmas 18(1), 012703 (2011)] to study these experiments. The results suggest that it is the support rod that is responsible for the helical structures persisting beyond stagnation. Furthermore, we find that as the radius of the support rod decreases (i.e., as the convergence ratio increases), the integrity and persistence of the helical modes diminish. In the limit with no support rod, we find that the structure of the final stagnation column is governed by the structure of the central precursor plasma column. These simulation results and their comparisons to experiment are presented.

中文翻译：

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与实验相比较的薄箔 Z 箍缩内爆的扩展磁流体动力学模拟

圆柱形箔衬垫，箔厚度约为 400 nm，通常用于大学规模的 Z 收缩实验（100 ns 中约 1 MA），以研究与大规模设施上的惯性约束聚变工作相关的物理学（例如，在桑迪亚国家实验室的 25-MA Z 设施上进行磁化线性惯性聚变工作）。使用超薄箔衬里通常需要一个中央支撑杆，以在内爆之前保持衬里靶组件的结构完整性。该支撑杆的半径限制了内爆所能达到的最大收敛比。在最近使用支撑杆和预施加轴向磁场的实验中，发现内爆箔等离子体中的螺旋不稳定性结构持续存在，因为箔等离子体停滞在棒上并随后扩展远离棒 [Yager-Elorriaga 等人，Phys. 等离子体 25(5), 056307 (2018)]。我们现在使用了 3D 扩展磁流体动力学模拟代码 PERSEUS（包括霍尔物理学）[CE Seyler 和 MR Martin，Phys. Plasmas 18(1), 012703 (2011)] 来研究这些实验。结果表明，支撑杆是造成螺旋结构在停滞之后持续存在的原因。此外，我们发现随着支撑杆的半径减小（即，随着收敛比增加），螺旋模式的完整性和持久性减弱。在没有支撑杆的极限，我们发现最终停滞柱的结构受中央前体等离子体柱的结构控制。介绍了这些模拟结果及其与实验的比较。