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The large dynamic particle inventory on the wall is investigated in ASDEX Upgrade and DIII-D with a fast local particle balance. Certain events lead to an inhomogenous neutral pressure distribution in the vessel, e. g. between main chamber and divertor region. We measure the pressure equilibration of this inhomogenous distribution and estimate wall outgassing or pumping rates necessary to satisfy the particle balance. Detailed particle balances for the divertor of ASDEX Upgrade after distruptions reveal large additional source and sink terms which decay with time constants of 10-20 ms over up to three orders of magnitude> Taking into account the finite pump time constants of the divertor chambers, ad- and desorption times of theorder of 1ms can be derived. Corresponding studies on DIII-D confirm these results, but with a larger spread of the decay times (10-80ms). The divertor pressure evolution after ELMs in both tokamaks also confirms the existance of such a fast reservoir.

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Authors: HAAS G, Max-Planck-Institut fur Plasmaphysik, Garching bei Munchen (DE);NEUHASER J, Max-Planck-Institut fur Plasmaphysik, Garching bei Munchen (DE);ASDEX UPGRADE TEAM, Max-Planck-Institut fur Plasmaphysik, Garching bei Munchen (DE);DIII-D TEAM, General Atomic, San Diego (US);MAINGI R, Oak Ridge National Laboratory, (US)
Bibliographic Reference: Article: Journal of Nuclear Materials, 266-269 (1999), 1065-1071
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