Plasma wall interaction during long pulse operation in Tore Supra

Increase of plasma density observed during long pulse operation is reported. The higher the injected and radiated energies are, the faster the increase of density appears. This behaviour correlated with oxygen and hydrogen plasma density increase is attributed to water desorption induced by wall heating due to the high radiated energy of the plasma. These surfaces are far from plasma and are not baked during the conditioning procedures usually used at Tore Supra. Conditioning evidence is seen during discharge series at high injected energy. But this improvement is prevented if disruptions occur in between. (C) 1999 Elsevier Science B.V. All rights reserved.