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The DIVIMP/NIMBUS onion-skin model has been used to calculate 2-dimensional plasma distributions of n(e), T(e) and T(i) in the Joint European Torus (JET) edge, based on boundary conditions measured across the targets with built-in Langmuir probes. Ohmic, L-mode and ELMy H-mode discharges were analysed. From the calculated 2D plasma profiles, values of Chi(perpendicular) sol(r) were extracted as a function of radial location within the SOL, showing that Chi(perpendicular) sol(r) increases with radius. At the separatrix Chi(perpendicular)(sol)(0) was in the range approximately 0.05 m{2}s{-1} to 1m{2}s{-1}, with the lowest values occuring for H-modes, (between edge-localized modes (ELM)). It was found that Chi(perpendicular) sol(r) approximates to (T(eu)(r)){-2}, where T(eu) is the electron temperature at the upstream end of the SOL flux tube. No clear correlation with magnetic field B(T) was found. The results are therefore not consistent with either Bohm or Gyro-Bohm scaling. Chi(perpendicular)(sol)(0) values were found to be weakly correlated with increasing plasma collisionality in the edge.

Additional information

Authors: ERENTS S K, JET Joint Undertaking, Abingdon, Oxon (GB);STANGEBY P C, JET Joint Undertaking, Abingdon, Oxon (GB)
Bibliographic Reference: Report: JET-P(97)51 EN (1997) 23pp.
Availability: Available from the Publications Officer, JET Joint Undertaking, Abingdon, Oxon, OX14 3EA (GB)
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