Optimization of pulsed intense magnetic field device for laser plasma experiment via inductively coupled coil

Abstract

Magnetized laser plasma has attracted a lot of attention in recent years especially in magnetized inertial confinement fusion, laboratory astrophysics, and industrial application. Pulsed intense magnetic field device is the core equipment of magnetized laser plasma experiment. Here in this work, an inductively coupled coil is developed to optimize the pulsed intense magnetic field device. The primary coil of a multi-turn solenoid is used instead of a single-turn coil. Then the energy of the solenoid is delivered to the secondary coil via inductively coupled transformer, which increases the current density markedly. The current generates a stronger magnetic field in the single-turn magnetic field coil. The influence of the diameter and the number of turns of the primary solenoid of the inductively coupled coil on the magnetic field are explored in experiment and simulation. It is found that for a discharge system of 2.4 μF capacitance, the optimized parameters of the primary solenoid are 35 turns and 35 mm diameter. The optimized magnetic field is 3.6 times stronger than that of the conventional directly connected single-turn coil. At a charging voltage of 20 kV, the peak magnetic field reaches 19 T in a magnetic field coil of 5 mm inner diameter. The inductively coupled coil made of CuBe solves the problem of coil expansion in intense magnetic field, and a peak magnetic field of 33 T is obtained at a charging voltage of 35 kV. The present approach creates stronger magnetic field environments. At the same time, the inductively coupled coil reduces the requirements for system inductance, so that components such as energy storage capacitors and switch can be placed far from the coil, which improves the flexibility of the experiment setup.

Upgraded pulsed magnetic field generator for Shenguang-II laser facility toward 30 T

“…Here we present two forms of magnetic field coils in figure 4. One is a triple-turn Cu coil of the same diameter (𝜙12 mm) wound with Kapton copper wire (18AWG, Accu-Glass #112697), which significantly increases the magnetic field strength without increasing the solid angle occupied, as shown in figure 4 The other is an inductively coupled coil [45] made of a higher yield strength material BeCu [41][42][43], as shown in figure 4 (c) and (d), which is a transformer structure consisting of a primary solenoid directly connected to the discharge system, a secondary coil surrounding the primary solenoid, and a magnetic field coil connected to the secondary coil. The primary solenoid coil is made of densely wound Kapton copper wire (14AWG, Accu-Glass #100715).…”

“…We analytically calculated the peak current in magnetic coil with different solenoid diameters and turns, as shown in figure 5. It shows that, for our device, when the turns of 35 ∼ 45 and the diameter of 35 ∼ 55 mm are selected for 20 kV discharge, the current in the secondary circuit reaches a peak of 180 kA [45]. In our experiments, we use a 35 turn, 35 mm diameter primary solenoid, with a coupling coefficient, the fraction of magnetic flux produced by the primary solenoid that links with the secondary coil, of 0.84.…”

“…Due to the weak yield strength of copper wires, it is difficult to obtain stronger magnetic field by merely increasing the voltage. However, with the significant increase in system capacitance, a high-inductance inductively coupled coil [45] made of higher yield strength BeCu material can be used as magnetic field coil, which will widen the range of magnetic field parameters considerably.…”