Quench propagation analysis in large solenoidal magnets

A quench analysis model that accurately accounts for experimental data, with no free parameters, was developed. The purpose of this analytical model is to incorporate, as much as practical, features of all MR magnet system components, describe their properties accurately, sequence efficiently through the quench event, and obtain reliable observable performance-critical parameters. The model treats adiabatic and convective processes and is well suited for optimizations because of good differential behavior in all quantities. This derives from the continuity to the first derivative of those properties modeled and the elaborate modeling of couplings, including AC losses, inductive, magnetic field, and convective processes. These optimizations have been exercized at the level of coil, cryostat, and protection scheme designs. The resulting algorithm was tested through a comparison of 4-, 6-, 8-, and 10-coil systems in producing equal central fields on the same-scale magnet. All coils were designed with a 3:2 aspect ratio, axial to radial, and located at respective Legendre polynomials zeros. The vessel assumed is the same in all cases. The multiple-coil analysis indicates that, from the quench point of view, the 4-coil design may be safest for reasons of low layer-to-layer voltages, maximum temperature, and cross-coil quench transit time. The uniform-size cryostat, however, is conducive to a lower level of quench inhibition. for this, and many other analyses, it is found that the event development is very weakly dependent on dump resistor sizing.<
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