Experimental evaluation of the magnetization process in a high Tc bulk superconducting magnet using magnetic resonance imaging

We measured the magnetic field distribution of a high Tc bulk superconducting magnet (c-axis oriented EuBa2Cu3Oy crystals) during the magnetization process using magnetic resonance imaging. Measurements were performed in the field cooling process from 100 to 50 K in a 4.74 T magnetic field and in the field reducing process from 4.74 to 0 T at 50 K. In field cooling; we observed a significant decrease in the gradient coil efficiencies caused by the Meissner effect. Analysis of the trapped field suggested the presence of temperature gradients; microcracks; and inhomogeneity in the bulk crystals.