5) Plasma-wall interaction and particles and heat extraction  (p  1 - 2 - 3 - 4 - 5 - 6 - 7 )

c) The different configurations

• The ergodic divertor : the results

Over a period of 10 years Tore Supra has intensively tested the possibilities of the ergodic divertor, which was dismantled in 2000 to start the machine up again in the CIEL configuration with an increased heat extraction capability (incompatibility between the ergodic divertor and the main component of the CIEL project: the toroidal pumped limiter).

The main results obtained are as follows :

• good control of the ergodic interference
• efficient screening of impurities
• strong capability to radiate

For example, we see here the screening effect of the ergodic divertor on impurities. Two successive identical argon injections are carried out, symbolised in green, one in limiter configuration, and the other with the ergodic divertor activated. We measure in blue the time evolution of the argon signal in the plasma centre. Before injection, the signal is nearly nil, corresponding to traces of argon in the machine. At the moment of injection, the signal soars, then drops, as the argon diffuses towards the plasma edge and is eliminated bit by bit from the centre. It can be seen that during the ergodic divertor phase, the same injection results in a much lower level of argon in the centre. This is the screening efficiency of the ergodic divertor, blocking impurities at the edge.

Analyses are currently being carried out to study the adaptation of an ergodic divertor to a next generation machine (that we imagine for the moment fitted with an axisymetric divertor). In the meanwhile, it is the German machine Textor that will take over study of the ergodic divertor, with the installation of a new device for a new start-up in 2002.