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Abstract

The neutral beam injection (NBI) efficiency for the TJ-II helical-axis stellarator has been studied by Monte Carlo simulations for the case of tangential injection. For benchmark purposes, two different NBI codes have been applied, which take into account the peculiar geometries of the NBI, vacuum vessel and helical-indented magnetic surfaces in TJ-II. The results obtained for various plasma parameters are discussed, comparing the co- and counter-heating efficiencies and considering loss mechanisms. The results from the two codes are in good agreement after allowing for differences in the magnetic field configurations. The Monte Carlo code, which treats the guiding centre part in magnetic coordinates, was used to investigate the influence of an assumed radial electric field on the heating efficiency. An interesting type of resonance which enhances fast orbit losses has been found when the ratio of the poloidal and toroidal frequencies of the fast ions is approximately 2. This critical ratio can be reached during slowing-down owing to the E x B drift.

Additional information

Authors: TEUBEL A, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE);GUASP J, CIEMAT para Fusión, Madrid (ES);LINIERS M, CIEMAT para Fusión, Madrid (ES)
Bibliographic Reference: Report: IPP 4/268 EN (1994) 9 pp.
Availability: Available from Max-Planck-Institut für Plasmaphysik, 8046 Garching bei München (DE)
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