Three-dimensional Simulation of Magnetic Flux Dynamics and Temperature Rise in HTSC Bulk during Pulsed Field Magnetization

The ability of superconductors to sustain persistent currents has been well exploited with (RE)BCO superconducting bulks, which can be magnetized to form a compact source of high magnetic field. However, thin films can also sustain persistent currents, which can be utilized by stacking them in layers to create a type of composite bulk. Such a stack is capable of trapping higher fields than a bulk, as reported in this paper. 12 mm wide, 55 µm thick commercial (RE)BCO tape from Superpower Inc was cut into 12 mm by 12 mm squares, stacked together and magnetized at temperatures between 10 and 77.4 K using a sequence of pulsed magnetic fields. The results are compared to a commercial 14 mm diameter YBCO bulk, showing that the stack of tapes outperformed the bulk at temperatures below approximately 60 K. Particularly high trapped fields were achieved below 50 K, with a maximum of 2.0 T at 10 K measured 0.8 mm from the stack surface. The maximum trapped field possible for a stack of tapes increases significantly with decreasing temperature down to 10 K, rather than saturating at a higher temperature as in the case of a bulk, due to superior thermal stability. The J c , thermal and mechanical properties of commercial (RE)BCO tapes give them great potential for use as trapped field magnets activated by pulsed magnetic fields.

Section: Stack Of Tapes and Bulk Samplementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Trapped fields up to 2 T in a 12 mm square stack of commercial superconducting tape using pulsed field magnetization

Patel

Hopkins

Glowacki

2013

“…Ohsaki et al investigated the magnetic flux motion in bulk superconductor during PFM using the given angled or cos curve model [21,22]. To understand the magnetic flux dynamics mechanism and temperature rise in the bulk superconductor, the simulation was performed by assuming that the critical current density in the GSBs was four times higher than that in the GSRs [23]. Recently, Ainslie et al also studied the inhomogeneity of the bulk superconductor under the magnetization process of PFM and FC, and the mechanical response of the bulk superconductor under field cooling was also analyzed [24,25].…”

Section: Introductionmentioning

confidence: 99%

Analysis of mechanical behavior in inhomogeneous high-temperature superconductors under pulsed field magnetization

Yong

Zhou

2020

Melt-textured large, single-grain REBCO (RE: rare earth element or Y) bulk superconductors have growth sector boundaries (GSBs) and growth sector regions (GSRs). The critical current density is dependent on the GSBs and the GSRs, which will influence the electromagnetic field and the temperature field distributions. REBCO bulk superconductors are brittle materials and during the manufacturing process, cracks and inclusions may exist, therefore it is necessary to analyze the mechanical response during the magnetization process. In this paper, the mechanical response of an inhomogeneous cylinder superconductor under electromagnetic stress and the thermal stress during the pulsed field magnetization process is studied. By solving the coupled magnetic and heat diffusion equations in association with a modified E − J power-law relationship, we can obtain the electromagnetic field and the temperature field distributions; then, the mechanical response of the bulk can be determined. The trend shown by our numerical simulation is consistent with the experimental results. Then we study the mechanical behavior of inhomogeneous high-temperature superconductors with and without a flux jump. The case without or with the SUS 304 ring is also analyzed.

“…Our studies in the past have revealed that the amount of residual trapped-field due to the preceding operation strongly affects the flux motion in the next operation and, hence, the amount of resulting trapped-field [13]. As a second approach we can improve the trapping ability by refining the material design such as the shape of the bulk [14], the introduction of artificial defects or holes [15,16], macroscopic J c distribution and so on. It is also evident that penetrating quantized fluxes are strongly affected by the local J c due to the presence of non-superconducting Y 2 BaCuO 5 (Y211) particles [17,18].…”

Section: Introductionmentioning

confidence: 99%

Magnetization behavior of RE123 bulk magnets bearing twin seed-crystals in pulsed field magnetization processes

Oka¹,

Miyazaki²,

Ogawa³

et al. 2015

Melt-textured Y-Ba-Cu-O high temperature superconducting bulk magnets were fabricated by the cold seeding method with using single or twin-seed crystals composed of Nd-Ba-Cu-O thin films on MgO substrates. The behavior of the magnetic flux penetration into anisotropic-grown bulk magnets thus fabricated was precisely evaluated during and after the pulsed field magnetization operated at 35 K. These seed crystals were put on the top surfaces of the precursors to grow large grains during the melt-processes. Although we know the magnetic flux motion is restricted by the enhanced pinning effect in temperature ranges lower than 77 K, we observed that flux invasion occurred at applied fields of 3.3 T when the twin seeds were used. This is definitely lower than those of 3.7 T when the single-seeds were employed. This means that the magnetic fluxes are capable of invading into twin-seeded bulk magnets more easily than single-seeded ones. The twin seeds form the different grain growth regions, the narrow-GSR (growth sector region) and wide-GSR, according to the different grain growth directions which are parallel and normal to the rows of seed crystals, respectively. The invading flux measurements revealed that the magnetic flux invades the sample from the wide-GSR prior to the narrow-GSR. It suggests that such anisotropic grain growth leads to different distributions of pinning centers, variations of Jc values, and the formation of preferential paths for the invading magnetic fluxes. Using lower applied fields definitely contributed to lowering the heat generation during the PFM process, which, in turn, led to enhanced trapped magnetic fluxes.