Abstract
Theoretical studies were undertaken to explain the salient features of the Radiative Improved mode (RI-mode) on TEXTOR-94: (a) it is shown that the linear increase in the energy confinement time with electron density can be explained by turbulence originating from the electron temperature gradient (ETG) driven modes—it is expected that the role of the dissipative trapped electron (DTE) mode may be strongly reduced in RI-mode discharges because of their high collisionality; (b) it is found that the toroidal flow curvature observed during the RI-mode with unbalanced co-injection can fully stabilize the drift resistive ballooning modes (DRBMs), whereas it can only marginally reduce the growth rate of the ITG and ETG modes—since confinements of particle, ion and electron temperatures are related, respectively, to the DRBM, ITG and ETG modes, this explains both the strong peaking of the density profile in the RI-mode and the comparatively weaker improvements in the ion and electron temperature profiles.
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