Influence of Inner Diameter and Height of Ring-Shaped REBaCuO Bulks on Trapped Field and Mechanical Stress During Field-Cooled Magnetization

摘要

In this paper, the trapped field B-z, thermal hoop stress sigma(cool)(theta) by cooling from 300 to 50 K, and electromagnetic hoop stress sigma(FCM)(theta) during field-cooled magnetization (FCM) from B-app = 6.3 and 9.4 T are investigated numerically for ring-shaped REBaCuO bulks with various inner diameters (I.D.) and heights (H) and reinforced by an Al alloy ring. For simplicity, an identical critical current density J(c) (B), which is a typical value at 50 K, is assumed in the simulation. The B-z value at the center of the ring bulk changes depending on the I.D. and H values of the ring bulk, which results from the different distribution of the superconducting current. As a result, the total hoop stress sigma(total)(theta) (=sigma(cool)(theta)+ sigma(FCM)(theta)) also changes for each ring bulk and each B-app because of the variation of the (sigma(cool)(theta) and sigma(FCM)(theta) values. The maximum sigma(total)(theta) value, which affects the bulk fracture at B-app = 9.4 T, increases with decreasing the height of ring bulk. These results can present guidelines for designing a trapped-field magnet using ring hulks.