The reduction of the critical current in Nb3Sn cables under transverse forces

The degradation of the critical current of impregnated Rutherford type Nb₃Sn cables was investigated as a function of the transverse force applied to the cable surface. Voltage-current characteristics were measured between 9 and 11 T by which the cable is supplied with the full transport current while a section on the broad side of the cable with a length of 40 mm is under pressure. A few samples were investigated as a function of the transverse force strands in the cable. It appears that the degradation of the strands is not uniform; for example, at 200 MPa some strands show 10% while others have 40% critical current degradation, also depending on the critical current criterion used. The global degradation of the cable is 12±2% at 200 MPa, though it is possible that a single bad strand in a cable limits the cable to below this value due to premature quenching of that strand