Local flux intrusion in HTS annuli during pulsed field magnetization

Abstract

During pulsed field magnetization of melt-grown HTS flux jumps can occur and the shielding current falls by 10-20 times. As the duration of pulse is shorter than the temperature relaxation time (<< 1 s), the circular current remains small during the field falling. The residual trapped field in the hole of the annulus has a direction opposite to that of the pulsed field. Small circular current and high critical current density are explained by the fact that flux moves through narrow regions of the annulus body. The angle of the sector with "soft flux" (i.e. a low Jc region) is estimated to be ∼ 7 deg.