Persistent magnetic fields trapped in high T c superconductor

A study of field trapping by the incomplete Meissner effect was performed on YBa2Cu3O7−x at 77 K on both sintered and oriented grain samples. Fields of up to BT=1280 G have been trapped in small, oriented grain, planar samples. Circulating persistent current densities of up to 4800 A/cm2 are calculated. Based on these values hollow cylinders of 2 cm i.d. will trap fields of 6000 G. Initial creep is about 10%/week for both types of samples. Creep rate varies as (BT/BT,max)2. BT, due to an external field B0, is BT∝(1−e−cB0/BT,max). Lamination and mosaic assembly steps for producing practical magnets have been performed.