Construction and testing of a high-homogeneity 55 T pulsed magnet for high-field nuclear magnetic resonance measurements

Abstract

High-field nuclear magnetic resonance (NMR) experiments call for the further development of pulsed magnets with a more practical winding structure and higher magnetic field homogeneity. This study presents the construction method and test results of a high-homogeneity pulsed magnet based on an optimized localized split structure. A winding craft using gap spacers was developed for the precise winding of split-gap transition wires. Magnetic field mapping was achieved in a steady-state low field of 32 mT using a Hall probe, with a measured magnetic field inhomogeneity of 198 ± 19 ppm over 1 cm diameter of spherical volume (DSV). The full-width at half-maximum (FWHM) of NMR spectra was adopted as a means of evaluating the magnetic field homogeneity in the pulsed field. In the optimal position, the measured FWHM is 42.2 ± 2.5 ppm at the low field of 7.7 T over a sample volume of 12.6 mm³. At the high field of 50 T, the FWHM decreases to 16.2 ± 0.8 ppm, which is a superior value achieved in similar reported pulsed magnets.