Comparison of direct inter-filament resistance measurement on Nb3Sn strands between University of Twente and ENEA

Experimental results of interfilament resistance measurements obtained with different facilities are compared. Two internal tin Nb3Sn strand types are tested at the University of Twente (UT) and ENEA Frascati. The direct interfilament resistance is measured with a standard four-point voltage-current (V- I) method. At the UT, a probe-station is used with micropoint-contact needles as voltage taps and current leads. At ENEA, the results are attained by a setup with microbonded contacts through thin aluminum (Al) wires. To extract values for the filament-to-matrix contact resistance and for the effective transverse resistivity from these experiments, finite element method simulations are required. The results of the experiments are in good agreement. In addition, we correlate the effective transverse resistivity, derived from the direct interfilament resistance measurement, to values measured and calculated from ac coupling loss.