Validation of a desktop-Type magnet providing a quasi-microgravity space in a room-Temperature bore of a high-gradient trapped field magnet (HG-TFM)

Abstract

<jats:title>Abstract</jats:title> <jats:p>The concept of a high-gradient trapped field magnet (HG-TFM), which incorporates a hybrid system of two (RE)BaCuO superconducting bulk components with different functions, was proposed in 2021 by the authors based on the results of numerical simulations. The HG-TFM as a desktop-type magnet can be a more effective way to generate a higher magnetic field gradient product of <jats:italic>B<jats:sub>z</jats:sub> </jats:italic> · d<jats:italic>B<jats:sub>z</jats:sub> </jats:italic>/d<jats:italic>z</jats:italic> (&gt;−1400 T<jats:sup>2</jats:sup> m<jats:sup>−1</jats:sup>, as calculated for a pure water), which can realize a quasi-microgravity space applicable for Space Environment Utilization on a laboratory scale. In this study, to validate the quasi-microgravity space in the HG-TFM, a prototype HG-TFM apparatus has been built using a slit-bulk TFM and stacked full-TFM (without slits) with inner diameters of 36 mm. After field-cooled magnetization from 8.60 T at 21 K, a trapped field of <jats:italic>B</jats:italic> <jats:sub>T</jats:sub> = 8.57 T was achieved at the center (i.e. at the bottom of a room temperature bore of 25 mm diameter outside the vacuum chamber), and consequently, a maximum <jats:italic>B<jats:sub>z</jats:sub> </jats:italic> · d<jats:italic>B<jats:sub>z</jats:sub> </jats:italic>/d<jats:italic>z</jats:italic> = −1930 T<jats:sup>2</jats:sup> m<jats:sup>−1</jats:sup> was obtained at the intermediate position between the slit-bulk TFM and the stacked full-TFM. Magnetic levitation was demonstrated successfully for bismuth particles and a pure water drop, which validates the quasi-microgravity environment in the HG-TFM. Based on numerical simulation results of the trapped field profile, it is concluded that the reason for the instability of the levitated targets is because of the repulsive magnetic force applied along the horizontal plane. The levitating state can be controllable, for example, by changing the operating temperature, which would allow objects to levitate statically along the central axis.</jats:p>