WB10-6
Simulation of three-dimensional quantized magnetic flux structure in superconducting wire in various magnetic field directions
Dec.3 17:20-17:35 (Tokyo Time)
Kyushu Institute of Technology, Fukuoka, Japan1
National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan2
National Institute of Technology Ariake College, Fukuoka, Japan3
Experiments have confirmed that the critical current density JC of the second type of superconductor depends largely on the direction of the magnetic field with plainer pins or cylinder pins. By numerically solving the TDGL equation, we visualized the movement of the quantified magnetic flux lines in the superconductor and used this to research the dependence of the JC on the θB under various pin conditions. [1]
We give the boundary condition corresponding to the normal component of the electric current density J is zero at the surfaces of the cube. Superconducting cube with different angle of applied fields as shown in Fig.1. The direction of the current density is along y‐axis direction and the direction of the external magnetic field is the rotation from z‐axis to x‐axis expressed by（Bx,By,Bz）=（BextsinθB,0,BextcosθB）where θB is the angle in zx‐plane.It is assumed that θB = 0° refers to the z‐axis direction. Hence, the vector potential can be given by （Ax,Ay,Az）=（0,BextxcosθB−BextzsinθB,0）for the rotating magnetic field. Calculations were made with Bext =0.1,0.2,⋯,0.6,J = 0.01,0.02,⋯,0.385,and θB = 0,30,45,60,90°.
We consider a superconducting cube of which side length is 10ξ in the vacuum. In addition, four different configurations of pins as shown in Fig. 2. In the region of the pins, we define the order parameter Ψ as 0.
Fig. 3 shows the simulation results of the angular dependence of JC at Bext = 0.2.In the case of plainer pin, JC decreases as the angle increases, and shows the highest JC when θB is between 0° and 60°.Although when θB is higher than 60°, the JC of the without pin is higher. In the case of other than plainer pin, JC decreases as the angle increases when θB is between 0° and 45°. Although JC increases as the angle increases when θB is between 45° and 90°. This is probably because the boundary between the superconductor and the vacuum works as a plainer pin.
Fig. 1: Superconducting cube with different angle of applied fields.
Fig. 2: Small superconducting cubes with different pins (a) spherical pin, (b) plainer pin, (c) Z cylinder pin, (d) Y cylinder pin.
Fig. 3: Angular dependence of the normalized critical current density on applied magnetic field.
[1] R. Yonezuka et al., Journal of Physics Conference Series 1293 (2019) 012018.
Keywords: Critical current density, time-dependent Ginzburg-Landau equations
