Tokamak Equilibrium Model with Finite Toroidicity Effects

An inverse aspect ratio (= e) expansion of a low-pressure, axisymmetric tokamak equilibrium is presented. The usual assumption of the s – α model (sharp pressure gradient in a small layer) is used to determine the first order correction in e for various physical quantities. In the infinite aspect ratio limit, the results of the standard s – α model are recovered. Finite toroidicity effects on ion temperature-gradient-driven ballooning modes are discussed and a numerical comparison between the two models is presented.