STRUCTURAL OPTIMIZATION OF THE SUPERCONDUCTING OUTSERT OF A 45-T HYBRID MAGNET

The National High Magnetic Field Laboratory (NHMFL), Tallahassee, Flor ida, in collaboration with the Francis Bitter National Magnet Laborato ry, MIT, is constructing a 45 T hybrid magnet system using cable-in-co nduit conductor (CICC) technology for the superconducting coils. In th is technology, superconducting wires are cabled and placed in a steel conduit that acts as the principal load-bearing member of the solenoid . In this paper, a structural optimization of the CICC is performed wi th the aim of reducing the coil mass required to generate the same fie ld strength. The constraints for the optimization are the upper limits values (allowable limits) for the three state variables: the average and peak values of equivalent von Mises stress, and hoop strain. Diffe rent geometric and material options were analyzed for optimum performa nce. Global-local finite element technique was used to conduct the str ess analysis. First, a global analysis, using effective material prope rties, was performed; followed by a local structural analysis. This pr ocedure was iteratively applied until one of the state variables just reached its allowable limit, thus yielding the optimized design. Signi ficant reductions were achieved in mass and stored energy of the magne t as a result of the optimization. (C) 1997 Elsevier Science Limited.