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Repetitive pellet injection into the ASDEX tokamak results in a long-lasting regime of improved particle and energy confinement. The strong density perturbations and changing gradients produced by pellet injection provide a promising opportunity to investigate the particle transport properties of OH and L-mode discharges. Sawtooth-free post-pellet density phases exhibiting low MHD activity are modelled. The enhanced peaking of the density profile is found not only to be due to the suppression of sawtooth dynamics but also to rely on variation of the particle transport. In comparison, the electron temperature profile is largely unaffected by pellet injection. The resulting inward pinch velocity is slightly enhanced and the corresponding cross-field diffusion coefficient D is strongly enhanced, over the prediction of the neoclassical theory. Moreover, analysis reveals that both coefficients increase monotonically with rising auxiliary heating power. Comparison with standard gas-fuelled discharges suggests that pellet injection reduces D in the bulk by the order of about 60%.

Additional information

Authors: MERTENS V, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE);KAUFMANN M, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE);LANG R ET AL., Max-Planck-Institut für Plasmaphysik, Garching bei München (DE)
Bibliographic Reference: Report: IPP 1/258 EN (1991) 15 pp.
Availability: Available from Max-Planck-Institut für Plasmaphysik, 8046 Garching bei München (DE)
Record Number: 199110894 / Last updated on: 1994-12-02
Original language: en
Available languages: en
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