Inductively coupled 30 T magnetic field platform for magnetized high-energy-density plasma studies

Enhanced X-ray emission arising from laser-plasma confinement by a strong transverse magnetic field

We analyze, using experiments and 3D MHD numerical simulations, the dynamic and radiative properties of a plasma ablated by a laser (1 ns, 10\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{12}$$\end{document}12–10\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{13}$$\end{document}13 W/cm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^2$$\end{document}2) from a solid target as it expands into a homogeneous, strong magnetic field (up to 30 T) that is transverse to its main expansion axis. We find that as early as 2 ns after the start of the expansion, the plasma becomes constrained by the magnetic field. As the magnetic field strength is increased, more plasma is confined close to the target and is heated by magnetic compression. We also observe that after \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sim 8$$\end{document}∼8 ns, the plasma is being overall shaped in a slab, with the plasma being compressed perpendicularly to the magnetic field, and being extended along the magnetic field direction. This dense slab rapidly expands into vacuum; however, it contains only \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sim 2\%$$\end{document}∼2% of the total plasma. As a result of the higher density and increased heating of the plasma confined against the laser-irradiated solid target, there is a net enhancement of the total X-ray emissivity induced by the magnetization.

Pulsed magnetic field device for laser plasma experiments at Shenguang-II laser facility

A pulsed intense magnetic field device was developed for the Shanghai Shenguang-II (SG-II) laser facility. The device using a double-turn coil with 12 mm diameter is capable of producing a peak current of 42 kA with 280 ns rising edge and 200 ns flat top width. A peak magnetic field of 8.8 T is achieved at the center of the coil. A two-section transmission line composed by a flexible section and a rigid section is designed to meet the target chamber environment of SG-II laser facility. The flexible section realizes the soft-connection between the capacitor bank and the target chamber, which facilitates the installation of the magnetic field device and the adjustment of the coil. The rigid section is as small as possible so that it can be inserted into the target chamber from any smallest flange, realizing elastic magnetic field configuration. The magnetic coil inside the chamber can be adjusted finely through a mechanical component on the rigid transmission line outside the target chamber. The adjustment range is up to 5 cm in both radial and axial directions with ∼50 µm precision. The device has been successfully operated on SG-II laser facility.

Portable pulsed magnetic field generator for magnetized laser plasma experiments in low vacuum environments

A portable pulsed magnetic field generator for magnetized laser plasma experiments in low vacuum environments is presented. It is based on a classical high-voltage discharge pulsed power system. A 95 kA peak current was delivered at a 65 kV discharge voltage, which generated a quasiuniform magnetic field of 12T in a Φ8 mm × 8 mm volume. A compact, sealed design was developed to avoid short-circuit breakdowns caused by an ambient low-pressure gas medium. Design improvements were made to the vacuum feedthrough, the transmission line, and the magnetic coil. The system worked well in a low vacuum environment for a laser plasma experiment using a gas target. But at intermediate ambient gas pressure, the ambient gas was ionized around the surface of the coil at first and then the ionized gas diffused inward and outward slowly, which affected the laser plasma image in the coil. Experiments and simulations indicated that the ambient gas was ionized by the induced electric field. We developed analytical models of the induced breakdown of the ambient gas to guide the experimental design of a gas target. The analysis can also be used in the experimental design of a solid target in an intense pulsed magnetic field of hundreds of tesla that the induced breakdown along solid's surface dominates the process.