Simulation studies on the magnetization of (RE)BCO bulk superconductors using various split-coil arrangements

Abstract

Simulation studies were conducted on the magnetization of (RE)BCO (RE–Ba–Cu–O, where RE represents a rare earth element) bulk superconductors using various split-coil arrangements by solving the critical state equation using the commercial software FlexPDE. A pair of coaxial coils of identical size is identified as an optimum arrangement for practical magnetization at 77 K by the ‘zero-field cooling’ technique. In general, the magnetization process is likely to be most effective when the outer radius of the coils lies between 100% and 50% of the sample radius. A relatively large coil pair is necessary for samples with either a smaller aspect ratio or larger values of Jc0. Two different regimes of flux penetration are found to be involved in the magnetization process. For a sufficiently small sample, the penetration field is determined by flux propagation from beneath the coil to the centre of the sample; for a sufficiently large sample, the definitive propagation route is from beneath the coil to the periphery of the sample. Effective split-coil magnetization occurs only in the former regime, and both penetration regimes are completely different from that involved in the solenoidal-coil magnetization process.

Trapped field properties of a Y–Ba–Cu–O bulk by pulsed field magnetization using a split coil inserted by iron yokes with various geometries and electromagnetic properties

“…Numerical simulation is a powerful tool to consider the obtained experimental results during PFM, and to understand the flux dynamics using electromagnetic and thermal equations. Several studies using the numerical simulation have been reported for PFM [17][18][19][20][21][22][23]. We have previously confirmed the advantage of the insertion of a soft iron yoke with a flat surface in the split coil numerically, and compared this to the case without the yoke [14,15].…”

Influence of Time-Varying External Magnetic Fields on Trapped Fields in Bulk Superconductors

“…The E-J power law (E α J n ) is used to simulate the non-linear electrical properties of the superconductors, where n = 21 and E 0 = 1 x 10 -4 V/m. J c0 is assumed to be 2 x 10 8 A/m 2 , which is consistent with the L measured material properties of the (RE)BCO bulk superconductors fabricated by the Cambridge Bulk Superconductivity Group [34].…”

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).…”