Pulse field magnetization of a ring-shaped bulk superconductor

Abstract

We have studied the pulse field magnetization of a YBCO bulk superconducting ring. In the experiments a 6 ms pulse magnetic field was applied to a ring-shaped YBCO superconductor with a 46 mm outer diameter, 16 mm inner diameter and 15 mm height, which was cooled by liquid nitrogen (77 K). Then, trapped magnetic field profiles were measured with a Hall sensor. For example, a single 1.2 T pulse field generated a hollow profile of the trapped magnetic field. In addition, the finite element method was used to solve the coupled problem of thermal and electromagnetic fields, where the power-n model was adopted for the E-J (E is the electric field and J is the current density) relation in the superconductor. A comparison between the results of experiment and analysis has shown that n = 6 gave good agreement between them. We have also discussed the current density distribution, temperature distribution, etc.

Critical state in finite type-II superconducting rings

“…In particular, the ring shape geometry can have a lower ratio of weight to trapped magnetic flux than a cylindrical bulk superconductor. 18 Furthermore, since the stress is the largest at the center of a disk, in a ring sample, one can avoid some mechanical problems by removing this central part of the superconductor. 19 Finally, we shall demonstrate in this work that the ring geometry presents some characteristics that make it an optimum geometry for the determination of J c from magnetic measurements.…”

Pulse Heating and Negative Magnetic Relaxation on Bulk HTS Annuli

“…To analytically evaluate the relative rate of the magnetic relaxation within idealized Bean model applied to thick-walled cylinders, knowledge of the temperature distribution in the magnetization process is sufficient [7]. In the case of real annuli and particularly for the PFM [10], the calculation of shielding currents is quite difficult even under the isothermal magnetization [11]. In our work, the shielding current distribution was determined from the measurements of the axial magnetic field B z (r) in the gap between the annuli (at z = 0).…”

3-D Transient Modeling of Bulk High-Temperature Superconducting Material in Passive Magnetic Bearing Applications

“…However, the frozen image method ignores effects related to the critical current density in the HTSC and therefore has only limited use. There has been, however, a considerable effort in the 2D and 3D modeling of the HTSC superconducting wire [8], [9] and to simulate the activation process in a bulk HTSC [9], [10]. Reference [8] gives a broad comparison of the 2D and 3D finite element methods to model HTSC using the commonly used potential formulation such as (i) the magnetic vector potential and the electric scalar potential (A-V, A method) and (ii) the magnetic scalar potential and the electric vector potential (T-Ω method).…”