Ionic instability thresholds in tokamaks
Linear ionic instability thresholds are numerically calculated for tokamaks. It is proved that the stability domain is determined by trapped-ion modes for positive values of eta(i) = d(logT(i))/d(logn(i)). The boundary is characterised by eta(i) greater than or equal to 1 and a threshold L(Ti)/R of order 0.2/(1 + T(i)/T(e)). This value is significantly smaller than previously predicted. Experimental temperature profiles in additionally heated discharges are usually marginal with respect to this criterion. It is also shown that marginal eigenmodes are low frequency, low wave-number modes, which may produce a very large transport once the ion temperature gradient threshold is reached.
Bibliographic Reference: Article: Physics of Fluids B, Vol. 4 (1992) No. 1, pp. 136-144
Record Number: 199210488 / Last updated on: 1994-12-02
Original language: en
Available languages: en