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The recent TEXTOR experiments have shown a high efficiency of the exhaust of injected helium by the ALT-II pump limiter from discharges with auxiliary heated plasmas of high densities and with strong edge cooling by neon radiation. In order to sustain steady thermonuclear burning in a reactor, the ratio of tau(alpha)(*) to tau(E) must be smaller than 15. Various processes in the limiter scoop channel, ie. interactions of charged and neutral particles during ionisation, dissociation, excitation, charge-exchange, nonlocality of the energy transport due to large mean free path lengths between Coulomb collisions essentially determine the efficiency of the pump limiter operation. In the present paper the existing model for the hydrogen neutrals and ions in the limiter scoop is extended to include a more realistic spectrum of neutral particles, and the energy transfer and the transport of helium atoms and ions are taken into account. As the most decisive parameter, the transformation factor (the ratio of the neutral density in the limiter chamber to the ion density at the scoop entrance) is computed. The results are compared with calculations by the EIRINE Monte-Carlo code and with recent TEXTOR data.

Additional information

Authors: TOKAR M Z, Forschungszentrum Jülich GmbH, Institut für Plasmaphysik (DE);REITER D, Forschungszentrum Jülich GmbH, Institut für Plasmaphysik (DE)
Bibliographic Reference: Article: Proceedings of the 19th Conference on Controlled Fusion and Plasma Physics, Vol. 2 (1992) pp. 739-742
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