Inducting technique and trapped field in ring-shaped superconductors

A comparative study of trapped flux depending on the inducting technique was made in superconducting rings. The inducting procedures used where the traditional field cooling with electromagnet (in this work FC1 or FC2) and the field cooling with a closed magnetic circuit placed through the ring's hole (FC3). The mentioned study was made by means of flux creep experiences in conventional samples and maps of trapped field in cut samples (current circulation disabled). The current induced in the samples was the critical value and the field trapped in the ring's wall depended on the magnetic field of FC1, FC2 or FC3. Data obtained from flux creep measurements exhibited the lowest relaxation rate for FC3. On the other hand, maps of trapped field show that the flux trapped was also the lowest when the induction was made by using FC3. The data depicted that samples with similar trapped flux density exhibited similarities in their relaxation rates with very different critical current.