Psfc/rr-08-9 Mechanical and Electromagnetic Transverse Load Effects on Superconducting Niobium-tin Performance

Cable-in-Conduit Conductor is the typical geometry for the conductor employed in superconducting magnets for fusion applications. Once energized, the magnets produce an enormous electromagnetic force and very large transverse loads are applied against the strands. This large force results in a degradation of the performance of the superconducting magnets. In this thesis work transverse load experiments on sub-sized cables, have been designed to study the mechanical and electrical transverse load effects on superconducting cables. Two devices to apply external mechanical loads to a cable have been developed and several different size cables have been tested simulating the International Thermonuclear Experimental Reactor (ITER) Lorentz stress conditions. The first device was designed to use a circular turn sample of a 36-strand cable. Four samples were successfully tested with this device and significant degradations of the critical current due to the external transverse loads have been measured. However, all samples showed unexpectedly large initial degradations that made an analysis of transverse load effects of the samples difficult. The second device was developed for a hairpin configuration. Three different size cables of a single strand, a triplet and a 45-strand cable were systematically tested using this method. This hairpin sample device has successfully operated and provided very reliable experimental data. The experimental results were difficult to explain by existing theories. A new model based on contact mechanics concepts has been developed to determine the number of contacts and the effective contact pressure among the strands in a cable. The model was used to analyze and accurately calculate the displacements of a cable under transverse