The effect of the ergodic divertor on electron thermal confinement
The thermal confinement within the confinement zone (values of q in the approximate range 1 to 2) of Tore Supra ohmically heated deuterium plasmas bounded by the ergodic divertor (ED) configuration is studied in a 1.5 D analysis of the local power balance. Although the edge electron temperature and mean electron density (n(e)) are both on average halved with application of the ED, the mean electron thermal diffusivity chi bar(e) shows the same density dependence as exhibited by standard ohmic limiter discharges, i.e., an Alcator-like inverse dependence on (n(e)) at low density (chi bar(e) approximately 2.5 x 1.0 E19/(n(e)), and a saturation at high density. The ion thermal transport at low to medium densities in both limiter and ED discharges is between 10 to 20 times that predicted by neoclassical theory. Comparing ED and limiter plasmas of the same density, a strong plasma decontamination is observed, with a reduction in Zeta bar(eff) by between 1.0 to 1.5. The effective decoupling of (n(e)) and Zeta bar(eff) by the ED and the invariant behaviour of chi bar(e) imply that electron thermal transport is only weakly dependent on Zeta bar(eff) in ohmic Tore Supra discharges.
Bibliographic Reference: Report: EUR-CEA-FC-1452 EN (1992) 23 pp.
Availability: Available from CEA, Département de Recherches sur la Fusion Contrôlée, Saint-Paul-lez-Durance (FR)
Record Number: 199211217 / Last updated on: 1994-11-29
Original language: en
Available languages: en