电磁驱动的磁瑞利-泰勒不稳定性失稳判据和模式选择研究

Magneto-Rayleigh-Taylor (MRT) instability appears to play an important role in the evolution of electromagnetically-driven high energy density (HED) plasmas. Usually, the MRT instability makes the HED plasma's behaviors deviate from that predicted by theories and numerical simulations, leading to difficulties of control of HED plasmas. This proposal studies the interfacial destabilization criterion and the mode selection of MRT instability through theoretical analysis and related experimental verifications. According to the similarities between the MRT instability and the phase transition, we focus on studying properties of MRT instability which was treated as a kind of general form of phase transition, including: the interfacial destabilization criterion of MRT instability under the assumption that the wave vector is chosen to be the order parameter, deducing the quantitative relation between the free energy and the mode of MRT instability, and acquiring the mode selection model of MRT instability. The research results of this proposal are useful for understanding the spontaneous generation mechanism of interfacial structures and are useful for approach of magnetized liner inertial fusion as well.

磁瑞利-泰勒不稳定性对电磁驱动的高能量密度等离子体的演化有重要影响，它通常使得系统的演化严重偏离人们的预期，导致系统难以控制。本项目针对磁瑞利-泰勒不稳定性的失稳判据和模式选择问题，采用相变的物理图像开展相关的解析理论分析和实验验证研究。基于磁瑞利-泰勒不稳定性与相变的相似性，重点阐述将磁瑞利-泰勒不稳定性处理为一种广义形式的相变的方法研究；以不稳定性波矢为序参量研究界面失稳判据；推导自由能与不稳定性模式的定量关系，获得模式选择模型。本项目的研究结论有助于加深对界面结构自发生成机制的理解，对磁化套筒惯性聚变研究具有参考价值。

基于朗道相变理论建立了Z箍缩驱动的磁瑞利-泰勒不稳定性现象的理论模型，该模型解释了磁瑞利-泰勒不稳定性的模式选择和演化规律。与铁磁体的自发磁化类似，磁瑞利-泰勒不稳定性是界面结构自发产生的结果。深入研究表明，磁瑞利-泰勒不稳定性的振幅是序参量，不稳定性的模式对应为热力学温度。磁瑞利-泰勒不稳定性属于一级相变，存在相变潜热，并且不稳定性波长正比于相变潜热的平方根。对于Z箍缩驱动的固体套筒内爆，相变模型的结果表明，套筒外界面的磁瑞利-泰勒不稳定性波长随时间快速增大并趋于某个极限值，极限的不稳定性波长与套筒的终态半径相当。基于“聚龙一号”装置开展了固体套筒内爆实验，获取了套筒外界面不稳定性演化的定量数据。将不稳定性的相变模型的预测结果与圣地亚实验室ZR装置上的实验结果和“聚龙一号”装置上的实验结果进行了对比，结果表明相变模型能很好地预测实验结果。