Characterization of Nb3Sn Rutherford Cable Degradation Due to Strands Cross-Over

Abstract

The quadrupole and dipole magnets for the LHC high luminosity upgrade will be based on Nb3Sn Rutherford cables that operate at 1.9 K and experience magnetic fields larger than 12 T. The Nb3Sn Rutherford cables are assembled via a planetary machine able to produce the trapezoidal geometry with the required mechanical tolerances (about ±0.01 mm) and low critical current degradation (<;5%). One of the critical aspects of Rutherford cable production is the control of the tension that is applied to each strand of the cable during the cabling process. If the strands are too loose during cabling, strands cross-over can be induced with a consequent locally high mechanical deformation and potential performance degradation. In this paper, the processes implemented at CERN for preventing and detecting strands cross-over during cables production are presented. The effect of cross-over on the electrical performance of a restack rod process Rutherford cable is also reported and discussed.