Numerical computation of the helical Chandrasekhar–Kendall modes

A new formulation is presented for numerically computing the helical Chandrasekhar–Kendall modes in an axisymmetric torus. It explicitly imposes ∇ · B = 0 and yields a standard matrix eigenvalue problem, which can then be solved by standard matrix eigenvalue techniques. Numerical implementation and computational results are shown for an axisymmetric torus typical of reversed field pinch and spherical tokamak.