Contact resistance and cable loss measurements of coated strands and cables wound from them

Calorimetric and magnetic studies of AC loss have been performed on 11-strand Rutherford cables made from multifilamentary strands with a variety of coatings. Interstrand contact resistance (R/sub c/) measurements supplemented these studies. R/sub c/s were deduced from the M-H determined eddy current loss as a function of ramp rate for four superconducting wires arranged in a rectangular geometry and put under a predetermined strain. It was found that: (1) the dominant factor which determines the R/sub c/ for uncoated strands is the level of surface oxidation (even for solvent cleaned strands); (2) strands can be de-oxidized either by an HCl etch or a vacuum anneal; and (3) strand coatings add significantly to the contact resistances of un-oxidized strands. It is concluded that contact resistance, and hence cable loss, is largely determined by the surface condition of the strands rather than the area ("spoon size") of the interstrand contact.<
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