M = 1 perturbation of reversed field pinch plasmas in the presence of filed errors arising from shell gaps

Behaviors of m = 1 kink modes of reversed field pinch plasmas are analyzed in the presence of field errors at shell gaps due to vertical field penetration. Perturbations in the vacuum and in the plasma are respectively expressed by using a class of modified Bessel functions and Bessel functions with m = 1 modes and matched on the boundary. It has been shown that m = 1 perturbation is amplified by the response of the plasma and its stability is deteriorated by the shell-gap field errors. Comparison with experiments is also discussed. (author)