The Study to Improve the Field Homogeneity of the NMR Relaxometry Magnets Using the Packaged HTS Bulks With Various Iron Rings

The compact magnet for NMR device that consists of a stacked high temperature superconducting (HTS) Gd-Ba-Cu-O bulk annuli was trapped by a held cooling method. However, it was difficult to trap the uniform magnetic held above 4.7 T (200 MHz-class NMR magnet) and held homogeneity under 0.01 ppm/cm3 at liquid nitrogen temperature (77.4 K) because of the low Jc-B characteristics of present HTS bulks. On the other hand, the strength and homogeneity of the magnetic held required for NMR relaxometry device are 1.5 T and 150 ppm/cm
³
respectively. It is easily to generate the trapped magnetic held over 1.5 T at 77.4 K using the stacked HTS bulks, but it is still hard to obtain 150 ppm/cm
³
held homogeneity with the conventional superconducting magnet (SCM) as the magnetizing magnets. Therefore, we have studied the compensation methods to improve the held homogeneity. In this paper, we proposed the packaged HTS bulk magnet consisted of HTS bulks annuli and various iron rings as the held compensation, and investigated it in analysis and experiment.