Effects of cross-sectional elongation and electron trapping on ion-temperature-gradient driven modes

Effects of shifted non-circular tokamak equilibria on eta (i) mode modes are investigated for peaked and flat density profiles. Ail advanced fluid model is used for the ion physics and effects of trapping are included in the model for the electron physics. An eigenvalue equation is derived in the electrostatic limit which is solved numerically using a standard shooting technique. We also consider the strong ballooning limit to get an algebraic dispersion relation to compare with the numerical results. The modes are investigated in a generalized s-alpha equilibrium model for relevant tokamak plasma parameters It is found that for peaked density profiles the effects of elongation are usually favorable whereas the effects of Shafranov shift are rather weak in agreement with previous results on the reactive eta (i)-mode. In addition it is found that effects of electron trapping are destabilizing on the eta (i)-mode, however the elongation scaling is preserved. For Rat density profiles, the effects of elongation may be destabilizing.