A New Experimental Setup to Measure Critical Current in Superconducting Strands Under Periodic Bending

Abstract

Cable-in-conduit conductors made of Nb 3 Sn strands, as envisaged in high-field magnets for fusion applications (e.g., the International Thermonuclear Experimental Reactor (ITER) project), have been shown to be prone to degradation of their current transport capability when subject to high electromagnetic forces (coming from the combination of a high current and a high magnetic field), particularly under cyclic loading. Although some optimization of the cable layout can be envisaged to mitigate this effect, the knowledge of the electrical properties of Nb 3 Sn strands under periodic bending (simulating in-cable operating conditions) is generally considered a needed characteristic for magnet designers and users. The French Alternative Energies and Alternative Energies and Atomic Energy Commission (CEA)/Institute for Magnetic Fusion Research (IRFM) has developed a new Versailles Project on Advanced Materials and Standards (VAMAS)-like mandrel in order to test under relevant field and temperature conditions high-field superconducting strands subject to periodic bending provided by the strand deformation under its own Lorentz force. The advantage of this setup is its similarity with the setup used in critical current measurements on a VAMAS mandrel, which makes its implementation in existing facilities quite easy and rather cheap, as well as possible direct comparisons with unbent samples on a classical VAMAS mandrel. This paper presents the design layouts and carefully depicts the assembly of the different tested samples. The first test results obtained on Nb 3 Sn strands are given and discussed.