Simulation study for magnetic levitation in pure water exploiting the ultra-high magnetic field gradient product of a hybrid trapped field magnet lens (HTFML)

A hybrid trapped field magnet lens (HTFML) is a promising device that is able to concentrate a magnetic field higher than the applied field continuously, even after removing an external field, which was conceptually proposed by the authors in 2018. In this study, we propose a new additional advantage of the HTFML, which could be applicable for magnetic levitation and separation. The HTFML device consisting of GdBaCuO bulk cylinder and GdBaCuO magnetic lens, after the magnetization process from an applied field, B_app = 10 T, can generate a maximum trapped field, B_c = 11.4 T, as well as an ultra-high magnetic field gradient product, B_z·dB_z/dz, over ±3,000 T²/m at T_s = 20 K, which is higher than that of existing superconducting magnets (SM) and large-scale hybrid magnets (HM). Through detailed numerical simulations, the HTFML device is considered for magnetic separation of a mixture of precious metal particles (Pt, Au, Ag and Cu) dispersed in pure water, by exploiting the magneto-Archimedes effect. The HTFML can be realized as a compact and mobile desktop-type superconducting bulk magnet system and there are a wide range of potential industrial applications, such as in the food and medical industries.Adaptable and Seamless Technology Transfer Program through Target-driven R&D (A-STEP), Japan Science and Technology Agency (JST), Grant No. VP30218088419 JSPS KAKENHI Grant No. 19K0524