Toward steady-state operation of a large Tokamak: the Tore-Supra experience

The distinctive feature of Tore-Supra is its super-conducting magnet, which provides a permanent toroidal field, therefore orienting its programs towards the control of multi-megawatt plasmas for long duration. Consequently, the inner vessel has been fitted with several high-efficiency water cooled elements in close interaction with the plasma. Three long pulse scenarios have been explored during the last experimental campaigns: (1) first, a 2 min pulse was obtained with a world record in injected energy: 280 MJ; (2) long pulses (up to 60 s) at high power (<7 MW) have been performed with a combination of ion cyclotron and lower hybrid frequencies; (3) finally, the input power has been maximised and almost 12 MW were launched in the plasma during a few seconds. The plasma–wall interaction becomes a critical issue, as injected power has to be removed steadily, and recycling fluxes must be controlled to maintain the density at its desired value and avoid plasma contamination. On the basis of these results, an enhancement in the capability to handle large input powers on a steady-state basis and to control the particles over long duration has been studied. This is the main motivation for the ‘Composants Internes Et Limiteur’ project, which consists mainly of the upgrade of the first wall components.