THE EFFECT OF TRANSVERSE LOADS UP TO 300 MPA ON THE CRITICAL CURRENTS OF NB3SN CABLES

In the framework of the development of an experimental 10 T Nb3Sn dipole coil for the LHC at CERN the effects of transverse stress on Rutherford type of Nb3Sn cables have been investigated. For this purpose a special facility was designed and taken into operation in which the voltage-current behaviour of short pieces of Nb3Sn cables can be investigated in a background field up to 11 T and an applied stress of 300 MPa. The repulsive Lorentz force of 250 kN, generated by a set of superconducting coils, is used to impress the cable over an area of 20x42 mm2 maximum, in presence of a transport current up to 40 kA. In this paper the testing equipment is described and the first results of the observed critical current degradation of two Nb3Sn cables are discussed. It was found, that current reduction starts immediately upon loading and that already at transverse compressive stress of 100 MPa the critical current at 11 T is reduced by more than 20 % for one cable and even about 60 % for the other one. Furthermore, it seems, that the edges of the Rutherford type of cable are much more sensitive to the applied force than the cross-over points of the strands.