Numerical simulation of the trapped field in MgB₂bulk disks magnetized by field cooling

Abstract

We performed a numerical simulation of the trapped field properties of MgB 2 bulk disks with different superconducting characteristics magnetized by field cooling. The temperature dependence of the trapped field B T () z , and the time dependence of the local field B t () z and temperature T (t) were calculated, and compared with experimental results. Since the measured critical current density J T B (,) c was used in the simulation, the results of the simulation reproduce the experimental results well. These results suggest that the value of B z and the trapped field profile can be estimated precisely for bulks of any shape and under any conditions, such as the operating temperature and applied field, using the measured J T B (,) c characteristics. The diameter and thickness dependence of B z was also calculated.

Recent Progress of <inline-formula> <tex-math notation="TeX">$\hbox{MgB}_{2}$</tex-math></inline-formula> Bulk Magnets Magnetized by Pulsed Field

“…The significant feature of the HIP#22 bulk is a small aspect ratio (d/t B ); that is, the HIP#22 is cylindrical rather than disk-shaped. The result is not supported by the numerical simulation for FCM [16], where the B z value slightly increases with increasing diameter (d) of the bulk, but is almost independent of the thickness (t B ). Increasing the t B and d values is not necessarily an effective solution to enhance the B z value.…”

Evaluation of Trapped Magnetic Field Properties in Superconducting MgB2 Bulk Magnets by Finite Element Method

“…Therefore, the trapped magnetic field of MgB 2 bulk magnet has been analyzed by the numerical calculation using finite element method (FEM). And it has been shown that the calculated result by FEM agrees well with experimental data [5]. In this calculation by FEM, they took into account of both electromagnetic and thermal equations for field-cooled magnetization (FCM) [5].…”

“…And it has been shown that the calculated result by FEM agrees well with experimental data [5]. In this calculation by FEM, they took into account of both electromagnetic and thermal equations for field-cooled magnetization (FCM) [5]. Hence, the calculation by FEM is relatively complicate.…”

“…It is to be noted that the temperature is slightly increases within 1 K during decreasing magnetic field. However, the maximum trapped magnetic field is reported to be less influenced by increasing temperature within 1 K [5]. The magnetic field dependence of the critical current density of the bulk MgB 2 at 5-37.5 K was measured by SQUID magnetometer [6], and it is used in the calculation by FEM.…”

“…They reported the temperature dependence of FCM process of trapped magnetic field, and the temperature raise within l K was depended on the rate of the external magnetic field decreasing in the final process of FCM. On the other hand, the maximum trapped magnetic field was almost constant for the rate of the external magnetic field decreasing [5]. Therefore, the magnetic field distribution in the MgB 2 bulk magnet in FCM could be calculated only the consideration of the electromagnetic equations at the constant temperature.…”