Current Averaging and Coil Segmentation in the Protection of Large Toroidal Superconducting Magnet Systems

Abstract

Table I compares several designs of the superconducting toroidal magnet arrays required to confine the plasma in a large fusion Tokamak device [^1–3]. Because of the high magnetic field and large plasma volume required in a power reactor, the magnetic energy stored in the toroidal field is very large. In order to avoid quenching—whether it is due to flux jumps, conductor motion, or other causes— before the design current is reached, cryostatic stabilization is usually preferred. Although there are some advantages, from the viewpoint of coil protection, to having a large number of coils in the torus, the actual number will probably be determined by factors such as field ripple in the plasma, manufacturing cost, access space, etc.

Table I Comparison of Toroidal Field Coil Parameters in Various Power Reactor Designs

The use of twenty-four coils seems to represent a plausible compromise of these factors. Because of the close proximity of a large number of coils, the inductive coupling plays a rather important role in the electrical behavior ofz the coils of such a close-packed toroidal array.

Research sponsored by the U. S. Energy Research and Development Administration under contract with Union Carbide Corporation.