Transport due to ion-temperature-gradient-driven magnetic drift modes

An advanced reactive fluid model is used to study the transport due to the toroidal ηi mode in the flat density limit. In this limit the density gradient scale length scales out from both the linear dispersion relation and the quasilinear transport coefficients. Simplified transport coefficients are derived for the flat density limit including also influence of electron trapping and are discussed in relation to the density modification experiments on the Tokamak Fusion Test Reactor (TFTR) [Proceedings of the 11th International Conference on Plasma Physics and Controlled Fusion Research (International Atomic Energy Agency, Vienna 1987), Vol. 1, p. 51]. The scaling properties with respect to various dimensionless parameters are discussed. In particular the scaling Xi ∼ ηi − ηith, which has also been derived by other authors for somewhat different situations, is found to be the relevant scaling in typical situations. A stabilizing and transport reducing effect of a high degree of electron trapping is pointed out.