Weizmann Institute of Science, Rehovot 76100, Israel.
Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375, USA.
Phys Rev Lett. 2019 Feb 1;122(4):045001. doi: 10.1103/PhysRevLett.122.045001.
The fundamental physics of the magnetic field distribution in a plasma implosion with a preembedded magnetic field is investigated within a gas-puff Z pinch. Time and space resolved spectroscopy of the polarized Zeeman effect, applied for the first time, reveals the impact of a preembedded axial field on the evolution of the current distribution driven by a pulsed-power generator. The measurements show that the azimuthal magnetic field in the imploding plasma, even in the presence of a weak axial magnetic field, is substantially smaller than expected from the ratio of the driving current to the plasma radius. Much of the current flows at large radii through a slowly imploding, low-density plasma. Previously unpredicted observations in higher-power imploding-magnetized-plasma experiments, including recent, unexplained structures observed in the magnetized liner inertial fusion experiment, may be explained by the present discovery. The development of a force-free current configuration is suggested to explain this phenomenon.
在气体填充 Z pinch 中，研究了带有预嵌入磁场的等离子体内爆中磁场分布的基本物理特性。首次应用的偏振塞曼效应的时间和空间分辨光谱学揭示了预嵌入轴向磁场对脉冲功率发生器驱动的电流分布演化的影响。测量结果表明，即使存在较弱的轴向磁场，内爆等离子体中的角向磁场也远小于根据驱动电流与等离子体半径的比值预期的值。大部分电流通过缓慢内爆的低密度等离子体在大半径处流动。在更高功率的内爆磁化等离子体实验中，包括最近在磁化惯性聚变实验中观察到的未解释的结构，可能会根据本发现来解释之前未预测到的观测结果。建议发展无作用力电流结构来解释这一现象。
