No abstract

The objective of this work was the design, the realization and the characterization of a superconducting coil, capable of generating a peak magnetic field of 100 mT. The measured degradation due to magnetic field and mechanical strain of the electrical properties of Bi-2223/Ag tapes has been taken into account in optimising the design. The resulting configuration consisted in a 10 double-pancakes coil realised with about 300 m of Bi-2223/Ag tape. The real degradation of each double pancake has been investigated by measuring the DC characteristic and the AC losses. The stacking configuration was finally defined by the measured differences among the critical current of each double-pancake. To minimise the effect of the perpendicular magnetic field degradation on the electrical properties of the whole coil, the pancakes with higher I c were mounted at the top and at the bottom. The DC electrical properties as well as the AC losses of the elementary components and of the whole coil have been measured and the results are presented and discussed in this paper.

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The reliable fabrication of robust, uniform, long length silver-sheathed Bi-2223 superconductor tapes capable of carrying high current densities represents a key factor towards the development of windings to be integrated in electric power devices. Bi-2223 tapes to be used for the fabrication of coils with silver alloy sheath having 19 and 55 filaments in unit length of 100 meters have been fabricated by the Powder-In-Tube method. The critical current density enhancement of Bi-2223 tapes by means of the optimisation of mechanical deformation and thermal treatment parameters is here presented. The realised Bi-2223 tapes have been deeply characterised by DC and AC measurements at different temperatures. To evaluate the capabilities of the multifilamentary tapes in the realisation of coils their electrical behaviour as a function of magnetic field and bending strain has been investigated.