CRITICAL CURRENT-MARGIN DESIGN CRITERION FOR HIGH-PERFORMANCE MAGNET STABILITY

A 'critical-current-margin. (CCM) design criterion for superconducting magnet stability is presented. It is applicable to high-performance magnets that operate at high current densities; these magnets have cooled conductor surfaces, but their calculated heat fluxes are well beyond recovery values. For stability of a magnet based on this CCM design criterion, disturbances must be limited in size but need not be eliminated nor localized. The CCM criterion is compared with the MPZ/Cold-End Theory. It is shown that this criterion offers a much higher confidence level of stability than the MPZ/Cold-End Theory. Furthermore, and unique to this theory, stability is independent of current density in the stabilizer. The CCM criterion is based on two magnet winding elements: heat transfer and composite conductor. In this criterion heat transfer must always remain in the nucleate boiling region throughout the operation of a magnet. The design emphasis is on more superconductor and less stabilizer. It is also demonstrated that the CCM theory works particularly well with conductors such as cabled conductors that have high ratios of cooled perimeter to cross-section. Experimental results are presented supporting this CCM design criterion. © 1979.