Collisionless trapped electron and ion temperature gradient modes in an advanced tokamak equilibrium

Abstract

The linear stability of coupled collisionless trapped electron (TE) and ion temperature gradient (ITG) modes is investigated in an International Thermonuclear Experimental Reactor [C. Gormezano et al., Nucl. Fusion 47, S285 (2007)]-like magnetic field configuration. An advanced fluid model in the electrostatic limit and the ballooning mode formalism are used to derive an eigenvalue equation. The growth rates and real frequencies of the most unstable modes and their eigenfunctions are calculated. The coexistence of unstable ITG and TE modes and their relative strengths with respect to the fraction of trapped electrons, wave vector, and local plasma parameters, such as density gradient, electron/ion temperature gradient, and ion to electron temperature ratio are analyzed. The influence of geometrical factors, such as local/global magnetic shear and magnetic field curvature on both ITG and TE modes is also discussed.