Ballooning-mode theory of trapped-electron instabilities in tokamaks

Employing the ballooning-mode formalism, the two-dimensional eigenmode equation for trapped-electron instabilities in tokamaks is reduced to a one-dimensional integro-differential equation along the magnetic field lines and then analysed both analytically and numerically. Dominant toroidal coupling effects are due to ion magnetic drifts which create quasi-bound states. The trapped-electron response can be treated as a perturbation and is found to de-stabilize the quasi-bound states.