E.T.S.I. Aeronáutica y del Espacio, Universidad Politécnica de Madrid, Madrid 28040, Spain.
Laboratory for Laser Energetics, Department of Mechanical Engineering, and Physics and Astronomy, University of Rochester, Rochester, New York 14623, USA.
Phys Rev E. 2018 Jan;97(1-1):011201. doi: 10.1103/PhysRevE.97.011201.
The theory of magnetic flux conservation is developed for a subsonic plasma implosion and used to describe the magnetic flux degradation in the MagLIF concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)10.1063/1.3333505]. Depending on the initial magnetic Lewis and Péclet numbers and the electron Hall parameter, the implosion falls into either a superdiffusive regime in which the magnetization decreases or a magnetized regime in which the magnetization increases. Scaling laws for magnetic field, temperature, and magnetic flux losses in the hot spot of radius R are obtained for both regimes. The Nernst velocity convects the magnetic field outwards, pushing it against the liner and enhancing the magnetic field diffusion, thereby reducing the magnetic field compression and degrading the implosion performance. However, in the magnetized regime, the core of the hot spot becomes magnetically insulated and undergoes an ideal adiabatic compression (T∼R^{-4/3} compared to T∼R^{-2/3} without magnetic field), while the detrimental Nernst term is confined to the outer part of the hot spot. Its effect is drastically reduced, improving the magnetic flux conservation.
磁通守恒理论是为亚声速等离子体内爆发展而来的，并用于描述 MagLIF 概念中的磁通退化[S. A. Slutz 等人，Phys. Plasmas 17, 056303 (2010)10.1063/1.3333505]。根据初始磁场刘易斯数和 Peclet 数以及电子 Hall 参数，内爆分为超扩散区（磁化强度减小）或磁化区（磁化强度增加）。对于这两种区域，都得到了半径为 R 的热点的磁场、温度和磁通量损失的标度律。奈斯特速度将磁场向外推动，使其与磁镜相互作用并增强磁场扩散，从而降低磁场压缩并降低内爆性能。然而，在磁化区，热点的核心受到磁绝缘，并经历理想的绝热压缩（与没有磁场时的 T∼R^{-2/3}相比，T∼R^{-4/3}），而有害的奈斯特项被限制在热点的外部。其影响大大降低，从而提高了磁通守恒。
