Superconductivity offers transmission of direct electrical current with zero losses. However, it is possible to only produce wires with finite length (< 1km) and to obtain required lengths, joints with zero or very low electrical resistance have to be developed. One of the fields which would greatly benefit from such joints are short-circuited superconducting magnets, where such superconducting joint would work as a persistent current switch, allowing us to disconnect the magnet from a power supply after it is charged and keep it in operation just by cooling it without further charging. Imrich Hušek and his colleagues continue their work on the development of the production process and optimization of the properties of a superconducting MgB2 joints between non-reacted single-core ex situ MgB2/Fe wires with a scarf architecture (Fig. 1).
As the to-be-joined wires two MgB2 wire types were prepared – one made from commercially obtained MgB2 powder and one type made from the same powder but further sieved to obtain powder with smaller particle size (80 μm to 21 μm). Several configurations of joints for both MgB2 wire types were prepared with varying powder particle size and applied mechanical deformation. Electrical properties were measured at temperatures relevant for superconducting magnets (4.2 K) and external magnetic fields up to 6 T and compared with the properties of not joined MgB2/Fe wires. The best performing joints, which had even better electrical properties than the wires by itself, were obtained when the applied mechanical loading caused 20% reduction of the original joint volume and MgB2 with particles smaller than 35 μm was used (Fig. 2). The exact values and production properties are listed in the linked article below.
Authors: Iimrich Hušek, Pavol Kováč, Tibor Melišek, Dušan Berek and Ľubomír Kopera
Link: https://iopscience.iop.org/article/10.1088/1361-6668/add426