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: J(c) (non Cu) in excess of 1000 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 I(c) at 6 T and 4.2 K of 15,500 A. In this paper we describe the results we obtained in an extensive campaign of I(c) measurements carried out bo th on cables and on strands, these last both in virgin state and extra cted from cable. The reliability of extrapolation from strands I(c) to cable performance is discussed as well as the degradation due to a cr oss-over in the cable thin edge.