DISSIPATIVE TRAPPED ELECTRON EFFECTS ON TOROIDAL ETA-I-MODE STABILITY

The stability properties of ion temperature gradient driven modes including the effect of dissipative trapped electrons is analyzed based on a toroidal two-fluid plasma model. It is shown that for finite trapping the eta-i-mode stability thresholds are discontinously shifted compared to the case without trapping. Furthermore the thresholds are not sensitive to the magnitude of the trapping. A stability requirement on the density scale length L(n) which has to be larger than about half the major radius R and an upper and a lower-eta-i stability threshold which grow linearly as +/-2L(n)/R are derived.