INFLUENCE OF CABLING ON CURRENT CARRYING PROPERTIES OF MgB2 SUPERCONDUCTORS
Superconductors based on magnesium diboride (MgB2) are promising for use in various devices, including high-current power lines developed at the European Center for Nuclear Research (CERN) for feeding superconducting magnets[1]. However, the MgB2 superconductors are very sensitive to the strain that unavoidably occur during a cabling process. Several studies [2-5] have been carried out recently to evaluate the electromechanical characteristics of MgB2 wires, both flat and round, in particular, the degradation of the critical current (Ic) on the applied strain for various types of MgB2 conductors has been estimated. Minimization of the critical current degradation requires an assessment of the deformations that inevitably exist in the manufacture of the cable however it is difficult to evaluate all possible strains that can occur during cabling of MgB2 conductors. To minimize the degradation of the critical current of MgB2 superconductors, the experimental approach is proposed that consists in a «step by step» estimation of the current characteristics of the wires at different stages of fabrication, followed by modification of corresponding components of the cabling machine. The paper presents some practical results on the influence of the cabling technology on critical current of round and flat MgB2 wires in the nickel matrix produced by Columbus Superconductor [6]. The currents of the samples taken at different stages of cabling are compared with the currents of the virgin wires, as well as with the currents that were achieved after upgrading the units of the cable machine. The temperature dependences of the critical currents of the samples investigated in the range of10 30 K are presented.