Magnetic measurement of transport AC losses in Bi-2223/Ag tapes

Magnetic nature of the losses in superconducting wire carrying AC current i mplies that it should be possible to determine these losses in a contactles s way. Ribbon-like samples are quite favorable for such an experiment, beca use a notable portion of magnetic flux related to losses 'escapes' the samp le volume and can be detected by an appropriate pick-up coil. In this case, a model describing the AC current penetration into the tape, based, e.g., on the critical state model, allows one to derive the losses from the pick- up coil signal. Because this signal is proportional to the number of coil t urns, extension of the accessible range of measured voltages (and losses) c an be achieved. We demonstrate the data obtained on a 1 cm long portion of a low-loss multifilamentary tape carrying AC current with frequency 35 Hz. The pick-up coil technique allowed us to reach loss level more than one ord er below the experimental limit for direct measurements. (C) 1998 Elsevier Science B.V. All rights reserved.