Concentric Slitting of a Ring-Shaped Bulk Superconductor for a Reduction in Circumferential Inhomogeneity of the Trapped Magnetic Field

• Published in: IEEE transactions on applied superconductivity 2011-06, Vol.21 (3), p.1588-1591
• Main Authors: Sekino, M, Yasuda, H, Miyazoe, A, Ohsaki, H
• Format: Article
• Language: English
• Subjects: Applied sciences; Bulk superconductor; Electrical engineering. Electrical power engineering; Electromagnets; Exact sciences and technology; growth sector boundary; Magnetic field measurement; Magnetic resonance imaging; Magnetic separation; magnetization; Nonhomogeneous media; Nuclear magnetic resonance; Superconducting magnets; Superconductivity; Trajectory; Various equipment and components
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2010.2091614

Magnetic field trapped in a superconducting bulk magnet has non-negligible inhomogeneity resulting from nonuniform superconducting properties. Counteracting the inhomogeneity is one of the challenging problems in applications of bulk magnets to NMR and MRI. In this study, we fabricated a bulk magnet with concentric slits for trapping a field with reduced circumferential inhomogeneity. A GdBaCuO superconductor, 60 mm in outer diameter, was sliced with a thickness of 2 mm. Three equally-spaced concentric slits were formed using a sandblasting technique. The magnets were cooled with liquid nitrogen in an external field of 600 mT. The z-component of trapped field was measured along circular trajectories. The magnet with slits exhibited smaller inhomogeneities of fields compared with an equal-sized one without slit. On a trajectory 30 mm in diameter, the field inhomogeneities of magnets with and without slits were 7% and 11%, respectively. On a 13-mm trajectory, the slits resulted in the reduction of inhomogeneity from 0.9% to 0.3%.