Experimental techniques for measuring the critical current in superconducting strands

The characterization of the critical current Ic in superconducting NbTi and Nb3Sn strands is carried out through a four-probe technique. Besides the dependence on temperature and magnetic field, which can be measured with a standard Variable Temperature Insert, the Ic of Nb3Sn samples is also sensitive to axial strain. For this measurement, specially dedicated probes can be used, among them we recall the Walters spring insert. Both systems and corresponding experimental techniques are here described.