Experimental Studies of Transverse Stress Effects on the Critical Current of a Sub-Sized Superconducting Cable

• Published in: IEEE transactions on applied superconductivity Vol. 17; no. 2; pp. 1386 - 1389
• Main Authors: Chiesa, L., Takayasu, M., Minervini, J.V., Gung, C., Michael, P.C., Fishman, V., Titus, P.H.
• Format: Journal Article
• Language: English
• Published: IEEE 01-06-2007
• Subjects: CICC; Conductors; Critical current; fusion; Magnetic field induced strain; Magnetic field measurement; Niobium; Strain measurement; Stress; superconducting cable; Superconducting cables; Superconducting magnets; Testing; transverse stress; {\rm Nb}_{3}{\rm Sn}
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2007.900986

Large superconducting magnets will play a central role in the success of the International Thermonuclear Experimental Reactor (ITER) and for the future of fusion energy. Cable-in-conduit conductors (CICC) will be used for the ITER magnets. As a CICC is energized, electromagnetic forces accumulate across the conductor, pressing strands transversely against one side of the conduit. We have developed a device to study the effect of transverse stress on a sub-sized cable using a mechanical load that simulates the Lorentz loads in the ITER Central Solenoid conductor. The test sample is a single turn (about 110 mm diameter) circular cable composed of 36 superconducting strands (cabling pattern of 3 x 3 x 4 ). The transverse stress is applied to the cable using a conical wedge that converts a vertical force into a radial (transverse) force. The vertical force is provided by a linear actuator. The stress on the cable is measured using two independent techniques: (1) strain gages applied directly to the ring where the cable is located and (2) a load cell located outside the cryostat. The device was successfully tested using a 20T, 190 mm bore Bitter magnet at National High Magnetic Field Laboratory (NHMFL), FSU, and a first series of tests were carried out showing a degradation of the critical current as a function of transverse stress. The maximum transverse stress was 100 MPa, for which the cable critical current degraded to roughly 30% of its initial value.