Among the large Tokamaks in operation around the world, Tore Supra has the unique feature of a superconducting magnet which provides a permanent toroidal field. Its main axis of research are therefore concentrated on the control of multi-megawatt plasmas during long duration, with the steady-state as ultimate goal. Consequently, Tore Supra inner vessel has been equipped with several water cooled elements in close interaction with the plasma.

To operate in steady state, both lower hybrid and fast waves have been used successfully to drive the current. A fully non inductive discharge in steady state regime (constant current with zero loop voltage) has been maintained for more than one minute with a feedback control of the lower hybrid power which drives the current. Enhanced performances related to current profile shaping have been intensively studied. H factors up to 1.8 (compared to Rebut-Lallia-Watkins scaling) have been obtained, correlated to the modification of the shear profile. In addition, an early attempt to control the current profile with a real time feedback loop on the lower hybrid waves index, has given promising result, and will be extended in a near future.

Injecting several megawatts during several tens of seconds implies to cope with considerable levels of power and energy on the first wall components. A world record has been achieved in 1996 with 280 MJ during a two minutes shot. An H factor of 1.6 is maintained during most of this discharge. Limitation in both power and energy have been observed and analysed. Simultaneously, plasma wall interaction becomes a critical issue for long pulse operation : recycling fluxes must be controlled to maintained the density at its desired value and avoid plasma contamination. Several geometries of pumped limiters have been tested. Very long evolution times have been put in evidence in plasma wall interaction physics.

On the basis of these results, an enhancement in the capability to handle large input powers and to control the particles over long duration, is planned. This is the main motivation for the Ç Composants Internes Et Limiteur È (CIEL) project, which consists mainly in an upgrading of the first wall components :
_ A new toroidal belt limiter will be installed in the lower part of the vessel. Made with CFC brazed on copper tube, it has been designed to removed up to 15 MW of convective power steadily,
_ A set of pumps will be able to evacuate all types of gas species through the toroidal throat of this limiter, allowing an improved density control.
_ A new water-cooled radiation screen will cover as much as possible the inner vessel, to avoid uncooled parts to be in interaction with the plasma.