Sutcliffe G D, Pearcy J A, Johnson T M, Adrian P J, Kabadi N V, Pollock B, Moody J D, Petrasso R D, Li C K
Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
Phys Rev E. 2022 Jun;105(6):L063202. doi: 10.1103/PhysRevE.105.L063202.
In laser-produced high-energy-density plasmas, large-scale strong magnetic fields are spontaneously generated by the Biermann battery effects when temperature and density gradients are misaligned. Saturation of the magnetic field takes place when convection and dissipation balance field generation. While theoretical and numerical modeling provide useful insight into the saturation mechanisms, experimental demonstration remains elusive. In this letter, we report an experiment on the saturation dynamics and scaling of Biermann battery magnetic field in the regime where plasma convection dominates. With time-gated charged-particle radiography and time-resolved Thomson scattering, the field structure and evolution as well as corresponding plasma conditions are measured. In these conditions, the spatially resolved magnetic fields are reconstructed, leading to a picture of field saturation with a scaling of B∼1/L_{T} for a convectively dominated plasma, a regime where the temperature gradient scale (L_{T}) exceeds the ion skin depth.
在激光产生的高能量密度等离子体中，当温度梯度和密度梯度不平行时，由比尔曼电池效应会自发产生大规模强磁场。当对流和耗散与磁场生成达到平衡时，磁场就会达到饱和。虽然理论和数值模拟为饱和机制提供了有用的见解，但实验验证仍然难以实现。在这篇论文中，我们报告了一项关于在等离子体对流占主导的区域中比尔曼电池磁场饱和动力学和标度关系的实验。通过时间选通带电粒子射线成像和时间分辨汤姆逊散射，测量了磁场结构和演化以及相应的等离子体条件。在这些条件下，重建了空间分辨磁场，得到了一幅对流主导等离子体磁场饱和的图像，在该区域温度梯度尺度（LT）超过离子趋肤深度，磁场标度为B∼1/LT 。
