Nonlinear MHD modeling in LHD plasmas with peaked pressure profiles

Nonlinear dynamics in Heliotron plasmas using a 3D nonlinear MHD simulation code in heliotron plasmas is studied. In the Large Helical Device (LHD) experiment, many MHD instabilities are observed. Especially, if the peaked pressure profile was sustained by the pellet injection, a collapse event, so-called the core density collapse (CDC), was happen. In nonlinear MHD simulations, it is expected the CDC is driven by the resistive ballooning mode. Recently, a new imaging diagnostics of the two-dimensional soft-X ray arrays is installed in the LHD. Using the new diagnostics, perturbations localized at the outward of the torus. That is a characteristic of the ballooning mode. So, it seems the ballooning mode is observed in the LHD experiments. However, to interpret the experimental observation, we need to know what kind mode patterns should be observed. In this study, we study 3D MHD equilibria with reconstructed pressure profile using a 3D MHD equilibrium code, which does not assume nested flux surfaces. And then, we will study nonlinear MHD simulations based on the 3D MHD equilibrium with the magnetic island. In this study, we note nonlinear saturation to compare with the experimental observation. (author)