Plasma equilibrium in a Tokamak

The paper summarizes the basic information on the equilibrium of a toroidal plasma column in systems of the Tokamak type. It considers the methods of maintaining a plasma in equilibrium with the help of a conducting casing, an external maintaining field and the iron core of a transformer. Attention is paid to the role of the inhomogeneity of the maintaining field. It is shown in particular how the shape of the column cross-section depends on the curvature of the lines of force of the maintaining field. For the case (which has practical importance) weak asymmetry of the field distribution in the transverse cross-section, this paper describes a uniform method of consideration, which takes into account the influence of different factors on the equilibrium position of the column. This method is used for calculating plasma equilibrium in a Tokamak model with a conducting casing. Account is here taken of the effect of gaps in the casing and of finite electrical conductivity. Some cases of plasma equilibrium which are outside the standard Tokamak scheme are also considered, such as equilibrium in a conducting shell having the shape of a racetrack, equilibrium where the whole current is transferred by relativistic runaway electrons and equilibrium at high plasma pressure βI ~R/a.