Mechanism of magnetic flux trapping on superconducting bulk magnetized by pulsed field using a vortex-type coil

Abstract

Numerical simulations of trapped field B z and temperature T have been performed for a cryo-cooled superconducting bulk disc after applying a magnetic pulse using a vortex-type coil. Results of the simulation qualitatively reproduced experimental results reported by Ida et al (2004 Physica C 412-414 638). Using the vortex-type coil, the magnetic flux does not intrude into the bulk from the periphery but intrudes from both surfaces of the bulk disc. The temperature rise was less than that obtained when using a conventional solenoid coil. The effect of the trapped field enhancement using a long pulse application is small, which suggests that down-sizing of the condenser bank used for the pulsed field magnetization is possible and that the use of the vortex-type coil is desirable for practical applications.

Simulation of Stacks of High-Temperature Superconducting Coated Conductors Magnetized by Pulsed Field Magnetization Using Controlled Magnetic Density Distribution Coils

“…For each coil, the trapped field first increases and then decreases with the applied field. This is consistent with numerous previous theoretical and experimental works on bulks [7][8][9][10][11][12][13][14]. Too low applied field cannot induce full currents in the sample; however, too high applied field will generate excessive heat, increase the temperature and reduce J c .…”

“…And the larger the gradient of the applied field generated by CMDCs, the larger the maximum trapped field. This finding shows consistency with [10][11], which finds that split coils may generate larger trapped field in HTS bulks compared to solenoids.…”

“…1. The latter is inspired by previous works on bulks which suggest that vortex coils have potential to improve the trapped field [10][11]. The CMDCs consist of a H pair of split coils.…”

“…1. The layer is 1 mm thick with λ equal 0.1 W/(m·K) in this model, which can be adjusted according to cooling efficiency [9][10].…”

“…However, the trapped field acquired by PFM is usually lower than that acquired by field cooling, because fast flux motions during the PFM generate considerable amount of heat and increase the temperature [5][6][7]. Studies by experiments and simulation have been reported to analyze the dynamics during the PFM and suggest strategies to improve the trapped field, but they mostly focus on HTS bulks [8][9][10][11][12][13][14][15][16]. In this study, a two-dimensional electromagnetic-thermal coupled model is constructed for stacks of HTS CCs magnetized by PFM.…”