Critical Current Studies on Nb-Ti Deformed-Strands

Abstract

The Nb-Ti hard conductors used in LHC dipole and quadrupole magnets are Rutherford cables composed of several tens of strands. During the cabling process, the strands are severely compacted especially at the thin edge of the cable. In order to assess, on the whole wire length, the deformation effect on the transport current of the wires, LHC-type Nb-Ti superconducting strands of various types were flattened by means of rollers. The critical current was then measured as a function of deformation and applied magnetic field at both 4.3 K and 1.9 K. The measurements were performed for both orientations (flat face perpendicular or parallel to magnetic field). The critical current density anisotropy of such deformed strands and the correlation with magnetization effects are discussed. This study permits to better understand and to quantify the critical current degradation of few percent observed in strands due to cabling. Comparisons with wires extracted from Rutherford cables are presented