STABILITY AND PROTECTION OF TORE SUPRA SUPERCONDUCTING COILS

The basic principles of stability provided by superfluid helium under atmospheric pressure are reviewed. Results of the development programme undertaken with prototype conductors and coils are described. They point out the outstanding cooling properties of superfluid helium together with the margin provided for stability. The present concept of protection for the TF coils of Tore Supra is based on two aspects: the first and main point is to guarantee that helium is really in the superfluid regime; and the second point is to ensure current decay in a quenching coil which is rapid enough to limit the temperature rise. These can be achieved thanks to fairly fast propagation inside the coil due to a rapid ejection of the cold fluid resulting from the increase in pressure.