Strain and Magnetic-Field Characterization of a Bronze-Route Nb3Sn ITER Wire: Benchmarking of Strain Measurements Facilities at NIST and University of Twente

A benchmarking experiment was conducted to compare strain measurement facilities at the National Institute of Standards and Technology (NIST) and the University of Twente. The critical current of a bronze-route Nb3Sn wire, which was fabricated for the International Thermonuclear Experimental Reactor (ITER), was measured as a function of axial strain and magnetic field in liquid helium at both institutes. NIST used a Walters' spring strain device and University of Twente used a bending beam (“Pacman”) apparatus. The ITER bronze-route wire investigated had a very high irreversible strain limit that allowed comparing data over a wide range of applied strain between -1% and +1%. Similarities of the data obtained by use of the two apparatuses were remarkable, despite the many differences in their design and techniques.