The use of the Bi-2223 superconducting tubes

The work is mainly devoted to the possibility of the use of the BPSCCO tubes as permanent superconducting magnets, i.e. to the increase of the critical current density J/sub c/ and the trapped magnetic flux density B/sub tr/. The obtained results are also applied for the superconducting current leads and fault current limiters. The Bi-2223 tubes were prepared by the isostatic pressing using a pressing mandrel and they were thermomechanically processed several times. It was shown that the texture formed during the process and favorably influencing J/sub c/ is more pronounced in tubes with thinner walls. With regard to this fact, a superconducting magnet composed of many thinner tubes was prepared. The trapped magnetic flux density in the hole of the magnet reached up to 0.5 T at 20 K and, after cooling the magnet at 15 K, the B/sub tr/ value of 0.5 T was maintained seemingly without relaxation for five days. This multi tubes magnet was also compared with one composed of two tubes of thicker walls. The J/sub c/ of about 1000 A/cm/sup 2/ (at 77 K and under self field of about 20 mT) achieved for the single tubes indicates an advantage of the use of relatively thin Bi-2223 tubes for the superconducting current leads and fault current limiters.