The characteristics of spatial homogeneity and strength of magnetic field for compact NMR magnets using stacked HTS bulks with various gap lengths

Abstract

A compact nuclear magnetic resonance (NMR) magnet is one of the new applications after a technique to enhance maximum trapped field of an high temperature superconducting (HTS) bulk. In design of a compact NMR magnet which consists of the stacked HTS bulk annuli, the issues of strength, spatial homogeneity and temporal stability by trapped magnetic fields are very important. This paper presents a study on the effects of magnetization field strength and gap length between stacked bulks for the compact HTS bulk NMR applications. Four-stacked HTS bulk magnet with ID 20mm and OD 60mm was prepared to investigate the optimized configuration. The thickness of each HTS bulk is 5mm, and the gap lengths from 0mm to 10mm were used as parameters in analysis and experiment, respectively. Four-stacked HTS bulk magnets with various gap lengths were tested at two different background magnetic fields of 0.5T and 2T at 77K. The optimized axial gap length was found out by analytical results, and the better magnetic field homogeneity and temporal decay property of trapped magnetic field were obtained by lower magnetization field in this experiments.