Electromagnetic Cycling and Strain Effects on Nb3Sn Cable-in-Conduit Conductors With Variations in Cabling Design and Conduit Material Properties

A parametric study has been conducted to quantify the effect in performance of cable-in-conduit conductors (CICC's) to changes in cable and conduit design. Measurements of current sharing temperature and critical current as a function of electromagnetic cycling and longitudinal strain were systematically performed on CICC's with common Nb3Sn internal tin strand. The designs varied in void fraction (0.30 or 0.36), long or short cable twist pitch, cable core patterns (6 around 1 or triplet), and conduit material property (stainless steel 316 or Haynes 242). Measurements were performed at the NHMFL in a test facility for conductor characterization with capability to 12 T, 20 kA, and 250 kN axial tensile load now modified to deliver temperature controlled supercritical helium to the CICC samples. Small differences have been measured in the current sharing temperature between CICC's with stainless steel jackets. However dramatic improvements in Nb3Sn of over 1 K have been found when Haynes 242 is used as the jacket material.