In a previous study, we achieved a record-high trapped field of BT=1.61 T at the center of the surface of an MgB2 bulk composite at 20 K by double-pulsed field applications using a split-type coil [1]. The MgB2 bulk composite consisted of the stacking of MgB2 ring bulk sandwiched by two thin oxygen-free copper (OFC) ring plates from both sides and a soft-magnetic iron (yoke) cylinder inserted into the bore of stacking. The yoke is well known to improve a trapped field by the pulsed-field magnetization (PFM), because it slows the intrusion velocity of vortices and then traps them effectively. Although the OFC plates were expected to act as a path of heat generated by the extensive vortex dynamics during PFM, we need to clarify the role of the OFC-plates to achieve the further enhanced trapped field. In this paper, we carried out the simulation study for the trapped field properties of the stacking of the OFC-MgB2-OFC cylindrical composite and found that the OFC plates did not act as the heat path but disturbed the intrusion of vortices due to the eddy current. The present results are in contrast to those by another group [2], the difference in which we will also discuss in the presentation.
[1] T. Hirano et al., Supercond. Sci. Technol. 33 (2020) 085002
[2] V. Cientanni et al., Supercond. Sci. Technol. 34 (2021) 114003
This work was partly supported by JSPS KAKENHI Grant Number JP21H01788 and the research grant program of The Futaba Foundation.