Optimisation of the magnet system of a 200 MW steady state tokamak

A study was undertaken to outline a long pulse D-T tokamak dedicated to plasma physics close to reactor conditions but still operating at limited values of fusion power (P/sub fusion/=200 MV) and amplification factor. Such a machine would not reach ignition and would not envisage a programme of irradiation of materials with high fluence. This makes it possible to slacken the technical constraints, in particular those related to the consequences of the irradiation of structural materials and of the magnets. Under inductive operation, the factor of amplification Q (P/sub fusion//P/sub heating/) was selected equal to 5, as a minimal value, making possible to have a significant heating power by the alpha particles. The duration of the current flat top would be about 500 s. Under these conditions, and taking into account an operation life of about 700 hours in D-T mode, an optimisation of the parameters of the machine was carried out, using superconducting magnets. The selected design criteria, as well physical as technological, are those of ITER-FDR, for which a large agreement exists in the scientific community. The magnet system design is described in detail. In parallel, another machine concept with copper magnets was studied for identical plasma parameters. The data base for copper steady state magnets is lighter than for superconducting magnets. Nevertheless, after having explored the aspects concerning thermohydraulics, mechanics, neutron irradiation and energy, the use of copper did not appear to be impossible.