Tore Supra--Status report concerning the superconducting magnet after the qualifying development program

One of the main features of the medium-size Tokamak, Tore Supra, starting now to be built in France, relies in its superconducting coils to provide the toroidal magnetic field. This magnet is built with a NbTi conductor inside a Cu-CuNi mixed matrix, cooled by a pressurized superfluid helium bath at 1.8 K and 1 atm. With this original arrangement, high values for the maximum field (9 T), current density and fast varying magnetic field amplitudes are simultaneously allowed; this is mainly due to the large heat transfer to the superfluid helium. A short description of the superconducting coils and of the associated cryogenic system will be presented. Their designs are now quite detailed, after the completion of a 2.5 year programme of component development and qualifying tests. Main highlights of its results will be shortly illustrated they concern basic transient heat transfer mechanisms inside superfluid helium, with the stability they provide to superconductor operation, as well as the technological solutions specifically retained for Tore Supra - a model coil has been built and tested against all plausible constraints coming from present Tokamak operation.