ABSTRACT
This chapter considers plasma equilibrium in the axisymmetric systems that is in tokamaks. It explores the effect of the gradient on the ellipticity and triangularity of magnetic surfaces in tokamaks. The plasma pressure influences the equilibrium displacement of centres of the magnetic surfaces and their shape. The chapter explains the equilibrium of a plasma in a tokamak with the circular casing assuming that the displacement due to the plasma pressure is important, whereas the ellipticity and triangularity are unimportant. It demonstrates the effect of deepening of the magnetic well due to plasma pressure and some combined effect on the magnetic well due to plasma pressure and shear. It discusses the influence of the plasma pressure on the shear and shows that the shear is defined not only by the radial derivative of the longitudinal current, as in the cylindrical case, but also by some toroidal effect proportional to the squared plasma pressure.
