AC LOSSES IN BI-2212 SUPERCONDUCTING MAGNET AT 20-K

A Bi-2212 oxide superconducting magnet has been cooled down to tempera tures around 20 K employing a Gifford-McMahon (G-M) cryocooler. An a.c . magnetic field with a peak value of 0.44 T is stably generated at fr equencies up to 0.25 Hz (0 T-->0.44 T-->0 T, 4 s per cycle) at almost- equal-to 20 K. The a.c. loss characteristics arising in the magnet are presented. The expected potential of the magnet for a.c. operation wi th a higher peak magnetic field is also discussed in terms of a.c. los s behaviour.