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K. Ichiguchi, B. A. Carreras
Multi-Scale MHD Analysis Incorporating Pressure Transport Equation for Beta-Increasing LHD Plasma
Date of publication:
22 IAEA Fusion Energy Conference, THS/P5-08
A multi-scale MHD numerical scheme is developed for the analysis of nonlinear evolution of betaincreasing plasma. The scheme is based on the iterative calculations of nonlinear dynamics based on the reduced MHD (RMHD) equations and three-dimensional static equilibrium. The equation for average pressure in the RMHD equation plays a roll of a transport equation that involves a heat source term and background pressure diffusion term. The heat source term is controlled so that the beta value should be increased in a constant rate. The scheme is applied to a configuration of the Large Helical Device (LHD), where ideal interchange modes are predicted to be unstable while beta values much higher than the predicted limit are obtained in the experiments. Local flat structure is generated in the background pressure profile due to the nonlinear saturation of the interchange modes. The generation reduces the driving force of the modes at higher beta value. Such self-organization in the pressure profile is considered to be the stabilizing mechanism in the plasma.
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