On tokamak equilibrium

Abstract

Large-aspect-ratio tokamak equilibrium is studied, including effects, such as ellipticity of the flux surfaces, of second order in the inverse aspect ratio. To facilitate the interpretation of experimental data, the analysis uses simple coordinates that are readily evaluated, rather than co-ordinates based on the exact flux surfaces. An explicit formula for the safety factor, including second-order terms, is presented, along with a brief discussion of rotational effects. The analysis assumes near-circularity of the outermost closed surface and low plasma pressure.