LONG-PULSE OPERATION WITH ACTIVELY COOLED LIMITERS

We present here the major results obtained with actively cooled plasma facing components during long pulse operation (plasma duration > 3 x surface temperature time constant = steady-state). Shots up to 120 s h ave been achieved in Tore Supra when the plasma was leaning on the lar ge inner toroidal actively cooled limiter with a moderate deposited po wer density heat flux (up to 0.3 MW/m(2)). For larger power density he at flux up to 4.5 MW/m(2) (design value), modular limiters have been u sed. A prerequisite for any actively cooled limiter is the absence of any cooling defect (crack II to the surface in the tile or non-correct bonding). If a defect is present it leads to a super-brilliance event (with its corresponding local power heat flux increase) which propaga tes. This deleterious effect is unfortunately a runaway effect.