Abstract
Bulk high-temperature superconductors (HTSs) that act as a trap field magnet establish a novel type of magnetic field source, which is significantly different from that of a permanent magnet or solenoid; therefore, they can be potentially used in magnetic-force-based applications. However, the primary issues related to the commercial use of the bulk HTS technology are established on the enhancement of trapped magnetic fields, as well as their reliability and reproducibility at temperatures achievable with off-the-shelf cryocoolers. This study presents experimental investigations on the strong trapped magnetic fields observed in commercial Y-Ba-Cu-O bulk HTSs produced as a double-sample stack, a cylindrical bulk, and a ring-shaped bulk. Consequently, a reliable and reproducible magnetic field of 9.5 T at 50 K was trapped in commercial Y-Ba-Cu-O assembled as a double-sample stack. In this case, shrink-fit encapsulation with either aluminum or stainless steel tube ensured equally effective reinforcement. Higher magnetization, although accompanied with partial flux jumps, yielded a trapped field of 16.85 T at 30 K, which is comparable to the reported record trapped fields. Finally, a maximum trapped field of 9.78 T - the strongest trapped field reported to date - was attained in the 6 mm hollow space of the ring-shaped bulk HTS.
Highlights
This study presents experimental investigations regarding the ability of the trapped fields and reproducibility of commercial off-the-shelf Y-Ba-Cu-O bulk high-temperature superconductors (HTSs) that were prepared as a double-sample stack, a cylindrical bulk, and a ring-shaped bulk
The obtained values are comparable to the reported record trapped fields; they were measuredin as-grown silver-free commercial Y-Ba-Cu-O samples, which suggests that further systematic reinforcement treatment can lead to even stronger (>17 T) trapped fields
3) Similar shrink-fit encapsulations using AISI 316 steel and 7075 aluminum tubes were used to evaluate the trapped field capability of the single bulk HTS, resulting in 6.65 T and 7.70 T measured at the surface of the standard and double-seeded bulk HTSs, respectively
Summary
Single-grain LRE-Ba-Cu-O (light rare earth, here Y, Sm, Nd, Gd) bulk high-temperature superconductors (HTSs), acting as a trap field magnet, establish a novel type of magnetic field source that is drastically different from that of a permanent. When appropriately cooled and magnetized, bulk HTSs can trap magnetic fields that are one order of magnitude stronger than those that can be provided by the best-performed Nd-Fe-B PMs [1]. In bulk HTSs, strong magnetic fields are generated in a free space, instead of being confined within a solenoid bore [2,3,4]. By comparing the performance of PM, solenoids, and bulk HTS devices, Oka [5] identified that bulk HTSs are advantageous magnet sources if the prioritized requirements
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