Harmonic Generation and Inverse Cascade in the z-Pinch Driven, Preseeded Multimode, Magneto-Rayleigh-Taylor Instability,Physical Review Letters

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Harmonic Generation and Inverse Cascade in the z-Pinch Driven, Preseeded Multimode, Magneto-Rayleigh-Taylor Instability
Physical Review Letters ( IF 8.1 ) Pub Date : 2022-06-21 , DOI: 10.1103/physrevlett.128.255001
D E Ruiz ₁ , D A Yager-Elorriaga ₁ , K J Peterson ₁ , D B Sinars ₁ , M R Weis ₁ , D G Schroen ₂ , K Tomlinson ₂ , J R Fein ₁ , K Beckwith ₁

Affiliation

The magneto-Rayleigh-Taylor instability (MRTI) plays an essential role in astrophysical systems and in magneto-inertial fusion, where it is known to be an important degradation mechanism of confinement and target performance. In this Letter, we show for the first time experimental evidence of mode mixing and the onset of an inverse-cascade process resulting from the nonlinear coupling of two discrete preseeded axial modes (400- and

550 − μ m

wavelengths) on an Al liner that is magnetically imploded using the 20-MA, 100-ns rise-time Z Machine at Sandia National Laboratories. Four radiographs captured the temporal evolution of the MRTI. We introduce a novel unfold technique to analyze the experimental radiographs and compare the results to simulations and to a weakly nonlinear model. We find good quantitative agreement with simulations using the radiation magnetohydrodynamics code hydra. Spectral analysis of the MRTI time evolution obtained from the simulations shows evidence of harmonic generation, mode coupling, and the onset of an inverse-cascade process. The experiments provide a benchmark for future work on the MRTI and motivate the development of new analytical theories to better understand this instability.

中文翻译：

z 夹点驱动、预置多模、磁-瑞利-泰勒不稳定性中的谐波生成和反向级联

磁-瑞利-泰勒不稳定性 (MRTI) 在天体物理系统和磁惯性聚变中起着至关重要的作用，众所周知，它是限制和目标性能的重要退化机制。在这封信中，我们首次展示了模式混合的实验证据以及由两个离散的预置轴向模式（400 和

550 - μ 米

波长）在使用桑迪亚国家实验室的 20-MA、100-ns 上升时间 Z 机器进行磁内爆的 Al 衬里上。四张射线照片捕捉到了 MRTI 的时间演变。我们引入了一种新的展开技术来分析实验射线照片，并将结果与模拟和弱非线性模型进行比较。我们发现与使用辐射磁流体动力学代码hydra的模拟具有很好的定量一致性。从模拟中获得的 MRTI 时间演化的光谱分析显示了谐波产生、模式耦合和反级联过程开始的证据。这些实验为 MRTI 的未来工作提供了一个基准，并促进了新分析理论的发展，以更好地理解这种不稳定性。

更新日期：2022-06-21

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