Analysis of the magnetic field in superconducting bulk magnets by the fluxoid dynamics method

Highlights: • We developed a novel calculation method to account for the reflection of the fluxoid in magnetic field calculations for superconducting bulk magnets. • The error in the B_z calculation using the proposed method was below 0.05 T at distances of more than 13 mm from the bulk center. • We expect the proposed technique to be more readily applicable and precise than existing models for magnetic field calculations of superconducting bulk magnets. -- Abstract: Highly precise magnetic field calculations must be conducted for superconducting bulk magnets at least 3 mm above the surface for cryocooler-cooling applications; in practice, calculations must be conducted for those at a distance of 5 mm from the surface. However, the reflection of the fluxoid affects the precision of the magnetic field calculations for superconducting bulk magnets but this effect has yet to be accounted for. Here, this effect was approximated and incorporated into the magnetic field calculations for superconducting bulk magnets. The numerical results were then compared with the experimental results. The data shows that the error was less than 4% at distances above 3 mm from the bulk surface in the magnetic field calculations performed by the new method. It is expected that the calculation error can be corrected in future studies by comparing the extrapolative semi-empirical model, like that presented here, with mesoscopic calculation models. These findings will be useful in the design of devices containing highly homogeneous superconducting magnets.