The influence of plasma elongation and Shafranov shift on the stability ofelectrostatic ion-temperature-gradient driven modes (ηi-modes) isinvestigated. An advanced fluid model is used for the ions together withBoltzmann distributed electrons. The derived eigenvalue equation is solvedboth analytically, in the strong ballooning limit, and numerically. It isfound that the effects of elongation change from stabilizing, for peakeddensity profiles, to destabilizing in the flat density regime. In addition, itis shown that the maximum growth rate is shifted towards shorter wavelengthsas the elongation increases. The effects of shaping on tokamak stability areexemplified with data from a Joint European Torus (JET) high-performance modedischarge.
Enhanced fusion performance due to plasma shape modification of simulated ITER discharges in DIII-D