TRAPPED ION MODE IN TOROIDALLY ROTATING PLASMAS

The influence of radially sheared toroidal flows on the Trapped Ion Mode (TIM) is investigated using a two-dimensional eigenmode code. These radially extended toroidal microinstabilities could significantly influence the interpretation of confinement scaling trends and associated fluctuation properties observed in recent tokamak experiments. In the present analysis, the electrostatic drift kinetic equation is obtained from the general nonlinear gyrokinetic equation in rotating plasmas [M. Artun and W. M. Tang, Phys. Plasmas 1, 2682 (1994)]. In the long perpendicular wavelength limit k(r) rho(bi)much less than 1, where rho(bi) is the average trapped ion banana width, the resulting eigenmode equation becomes a coupled system of second order differential equations for the poloidal harmonics. These equations are solved using finite element methods. Numerical results from the analysis of low and medium toroidal mode number instabilities are presented using representative Low confinement mode (L-mode) experimental data followed by a discussion of numerical results. (C) 1995 American Institute of Physics.