Inhomogeneities in a current-carrying conductor promote non-uniform heating and expansion through the complex feedback between current density, electrical resistivity, Ohmic heating, temperature, and hydrodynamics. Three-dimensional-magnetohydrodynamic (3D-MHD) simulations suggest that μm-scale resistive inclusions or voids seed local overheating and through hydrodynamic explosion generate continuously growing craters which become several times larger than the initial perturbation. The ejected mass is the genesis of an electrothermally driven plasma filament which develops at lower current than plasmas on uniform surfaces adjacent to the defect. This result suggests that 1D or even 2D treatments are largely inadequate for detailed prediction of plasma formation. To test computational predictions, z-pinch experiments driven to 1 MA studied ultra-high-purity aluminum rods which were then machined to include pairs of quasi-hemispherical voids or “engineered defects (ED)” on the current-carrying surface. ED are the dominant current-density perturbation and reproducibly drive local overheating which can be compared with 3D-MHD simulation. Data from high-resolution-gated imagers of visible surface emissions confirm many simulation predictions, including the surface topography of local overheating, and the propensity for neighboring ED to prematurely source plasmas which then connect to form a plasma filament. Results also provide conditional support of theory which suggests heating similarity; that is, heating is independent of ED size for geometrically scaled ED.

中文翻译：

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通过添加微米级表面缺陷以可控方式引发高电流密度导体的爆炸

载流导体中的不均匀性通过电流密度、电阻率、欧姆加热、温度和流体动力学之间的复杂反馈促进了非均匀加热和膨胀。三维磁流体动力学 (3D-MHD) 模拟表明μm 级电阻包裹体或空隙种子局部过热并通过流体动力爆炸产生持续增长的陨石坑，这些陨石坑变得比初始扰动大几倍。喷射出的物质是电热驱动的等离子灯丝的起源，该灯丝在比缺陷附近的均匀表面上的等离子更低的电流下产生。这一结果表明，一维甚至二维处理在很大程度上不足以详细预测等离子体形成。为了测试计算预测，驱动到 1 MA 的 z-pinch 实验研究了超高纯度铝棒，然后将其加工成在载流表面上包括成对的准半球形空隙或“工程缺陷 (ED)”。ED 是主要的电流密度扰动，可重复地驱动局部过热，可与 3D-MHD 模拟进行比较。来自可见表面发射的高分辨率门控成像仪的数据证实了许多模拟预测，包括局部过热的表面形貌，以及相邻 ED 过早产生等离子体的倾向，然后连接形成等离子体灯丝。结果还为表明加热相似性的理论提供了条件支持；也就是说，对于几何缩放的 ED，加热与 ED 尺寸无关。结果还为表明加热相似性的理论提供了条件支持；也就是说，对于几何缩放的 ED，加热与 ED 尺寸无关。结果还为表明加热相似性的理论提供了条件支持；也就是说，对于几何缩放的 ED，加热与 ED 尺寸无关。