Calorimetric Measurements of the Effect of Nickel and Stabrite Coatings and Resistive Cores on AC Loss in Accelerator Cables under Fixed Pressure
Calorimetric measurements of AC loss on long three- and four-layer stacks of Rutherford cable have been made with the applied field both normal to (face-on, FO, orientation) and parallel to the plane of the cable. Cables studied had bare-Cu, Ni-plated, and stabrite-coated strands; the latter were provided with metallic or insulating interlayers (cores) of, respectively, unalloyed Ti, stainless steel, and kapton ribbon. The cable packs were clamped in a fixture to a pressure of 75 MPa and heat treated for several hours at temperatures of 185 to 250°C. After cooling, the clamped cables were transferred to the calorimeter and measured without releasing the pressure. From the field-ramp-rate dependence of coupling loss the interlayer- and intralayer interstrand contact resistances, R⊥ and R|| were deduced. The results were interpreted against a background of earlier “cure-release-repressurize” calorimetric measurements of cable loss as well as direct measurements of contact resistance. Depending on the curing temperature the bare-Cu cable exhibited the highest (Tcure = 250°C) and the lowest (Tcure = 185°C) FO losses. Nickel plating resulted in a cable that was much less sensitive to curing temperature. All the core-type cables (Tcure = 185 and 200°C) exhibited FO loss that was mid-way between those of bare Cu (Tcure = 185°C) and Ni-plated (Tcure = 200°C) cables.
KeywordsHeat Treat Contact Resistance Calorimetric Measurement Coupling Loss Bare Copper
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