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

Abstract

In this paper, the trapped field B z , thermal hoop stress σ θ cool by cooling from 300 to 50 K, and electromagnetic hoop stress σ θ FCM 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 σ θ total (= σ θ cool + σ θ FCM ) also changes for each ring bulk and each B app because of the variation of the σ θ cool and σ θ FCM values. The maximum σ θ total 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 bulks.