PRESSURE AND INDUCTANCE EFFECTS ON THE VERTICAL STABILITY OF SHAPED TOKAMAKS

Numerical calculations are presented to show the influence of pressure and inductance on the vertical stability of shaped tokamaks. High val ues of epsilon beta(p) improve the vertical stability of dee shaped to kamaks but are destabilizing for an inverse dee. For elongated cross-s ections, the pressure effect is well described by a linear dependence of the maximum value of the stable internal inductance l(i) on epsilon beta(p), with a coefficient that depends on the geometry and increase s with the triangularity. Stability diagrams are shown in terms of l(i ) versus epsilon beta(p) for TCV- and DIII-D-like cross-sections. Curr ent profile effects depend critically on the wall configuration: low v alues of l(i) are stabilizing if the wall is close, but increase the d riving farce of the instability in the absence of a wall. The competit ion between these two effects is considered for a configuration with d iscrete external conductors.