The Electrothermal Instability on Pulsed Power Ablations of Thin Foils
The Electrothermal Instability on Pulsed Power Ablations of Thin Foils
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DOI：
10.1109/tps.2018.2873947
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发表时间：
2018-10
影响因子：
1.5
通讯作者：
A. Steiner;P. Campbell;D. Yager-Elorriaga;N. Jordan;R. Mcbride;Y. Lau;R. Gilgenbach
中科院分区：
文献类型：
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作者：
A. Steiner;P. Campbell;D. Yager-Elorriaga;N. Jordan;R. Mcbride;Y. Lau;R. Gilgenbach
给出了薄铝箔大气烧蚀的光学成像结果。这些实验被用来评估由电热不稳定性(ETI)引起的温度扰动的增长。ETI已经被证明在脉冲功率驱动的初始固体金属靶材的烧蚀中播撒磁流体动力学不稳定性，这是依赖于稳定的线性内爆的脉冲功率驱动等离子体物理中的各种程序感兴趣的主题。实验观测表明，垂直于电流方向的温度微扰呈指数增长，其增长率与线性ETI理论一致。在体箔中沉积足够的能量以克服汽化潜热之前，观察到高温区进入汽相，这表明能量沉积速率在空间上具有显著的异质性。这些扰动的增长率以电流密度的平方为尺度，这是长波长ETI结构的预测行为。这些结构的发展不受铝箔表面物理变形的影响，但受到铝箔载荷中局部高阻区的显著影响。随着时间的延长，观察窗口显示了从垂直细丝到平行细丝的转变，这一点很重要，因为预计当块材箔材料转变到等离子体状态时，ETI将改变方向。总而言之，这些结果为许多关于ETI的理论预测提供了实验验证。
Presented are results from the optical imaging of atmospheric ablations of thin aluminum foils. These experiments were performed to evaluate the growth of temperature perturbations attributed to the electrothermal instability (ETI). ETI has been shown to seed magnetohydrodynamic instabilities on pulsed power-driven ablations of initially solid metallic targets, a topic of interest to various programs in pulsed power-driven plasma physics that depend on stable liner implosions. Experimental observations presented herein demonstrate exponentially growing temperature perturbations perpendicular to the direction of current with growth rates consistent with the linear ETI theory. High-temperature regions were observed to enter the vapor phase before sufficient energy had been deposited in the bulk foil to overcome the latent heat of vaporization, indicating a significant spatial heterogeneity in energy deposition rates. The growth rates of these perturbations scale as the square of current density, the predicted behavior for long-wavelength ETI structures. The development of these structures was unchanged by physical deformation of the foil surface, but dramatically influenced by incorporating areas of local high resistance in the foil loads. Extending the observation window in time showed a transition from perpendicular to parallel filaments, which is significant because ETI is predicted to switch orientations when the bulk foil material transitions into the plasma state. Collectively, these results provide an experimental validation of many theoretical predictions regarding ETI.