Mercier stability improvement in nonlinear development of LHD plasma

A stable path to high-beta plasmas is investigated for an inward-shifted LHD configuration. An improvement of Mercier stability is observed due to the nonlinear saturation of the resistive interchange modes. For this study, a multi-scale numerical scheme is used. In this scheme, the beta value is increased by adding a small pressure increment to the background pressure. We focus on the dependence of the Mercier stability on the profile of the pressure increment. It is found that the total pressure profile approaches a profile marginally stable to the Mercier criterion when the pressure increment has a fixed profile. (author)