Critical current measurements of the cable for the superconducting dipole prototypes for the Large Hadron Collider

The specifications of the NbTi/Cu cable for the superconducting dipole of the LHC are very demanding: Jc (non Cu) in excess of 1,000 A/mm2 at 8 tesla and 4.2 K, with filament diameter of 5--6 microns. One type of cable is composed of 26 strands with a required critical current at 8 T and 4.2 K of 13,000 A and the other one has 40 strands with Ic at 6 T and 4.2 K of 15,500 A. In this paper the authors describe the results they obtained in an extensive campaign of Ic measurements carried out both on cables and on strands, these last both in virgin state and extracted from cable. The reliability of extrapolation from strands Ic to cable performance is discussed as well as the degradation due to a cross-over in the cable thin edge