Turbulence and energy confinement in Tore Supra ohmic discharges
Results on confinement and turbulence from a set of ohmic discharges in Tore Supra are discussed. Attention is focused on the saturation of the energy confinement time and it is emphasised that this saturation could be explained by a saturation of the electron heat diffusivity. Ion behaviour is indeed governed by dilution and equipartition effects. Although the ion heat transport is never neoclassical, there is no enhanced degradation at the saturation. This behaviour is confirmed by turbulence measurements given by CO(2) laser coherent scattering. The density fluctuations level follows the electron heat diffusivity variations with the average density. Waves propagating in the ion diamagnetic direction are always present in turbulence frequency spectra. Thus, the saturation cannot be explained by the onset of an ion turbulence. The existence of an ion turbulence at the edge at all densities cannot be excluded. However, this ion feature in scattering spectra could be explained by a Doppler shift associated with an inversion point of the radial electric field at the edge.
Bibliographic Reference: Report: EUR-CEA-FC-1454 EN (1992) 25 pp.
Availability: Available from CEA, Département de Recherches sur la Fusion Contrôlée, Saint-Paul-lez-Durance (FR)
Record Number: 199211218 / Last updated on: 1994-11-29
Original language: en
Available languages: en