POWER DEPOSITION TO THE FACING COMPONENTS IN TORE-SUPRA

The modifications of the power scrape-off length, lambda-q and power deposition are studied for various configurations in ohmic Tore-Supra plasmas. The plasma is either touching the horizontal limiter alone, the full set of six pump limiters or the inner bumper limiter. All configurations are with and without the ergodic divertor system energized. From a comparison of the infrared images of the limiter we derived that the lambda-q for power deposition was slightly less than 9 +/- 1 mm in ohmic plasmas which is in agreement with the predicted design value of 10 mm. Using the six limiters, instead of one, does not modify lambda-q significantly, but leads to small asymmetries. The power is shared by all the limiters and the maximum surface temperature on the horizontal limiter decreases. These lambda-q values have been independently determined by calorimetric measurements on the integrated energy deposition on the horizontal limiter and other internal structures 5 cm into the scrape-off layer. These values agree with the infrared measurements in the two cases. In the presence of the ergodic divertor we observe a broadening of the scrape-off layer, the e-folding length for power deposition reaching 2.5 cm. Large asymmetries in the power deposition can be seen on the front face of the limiter, leading to the formation of hot spots at the leading edges.