Multi-Modal analysis of linea­­r MHD response to resonant magnetic perturbations in DIII-D plasmas*

The impact of plasma triangularity on the plasma response to 3D magnetic perturbations for DIII-D plasmas is investigated to gain insight into its role in the suppression of edge localized modes. This work is motivated by empirical evidence that shows the dynamics behind ELM suppression can be significantly altered by the 2D plasma shaping, namely the triangularity, to the point where ELM suppression may not be achieved with applied 3D fields [1].  Here, kinetic equilibria with self-consistently varied triangularity, pedestal density, and plasma beta obtained using the SEGWAY framework are processed using GPEC to calculate the 3D plasma response. Preliminary results show qualitative agreement between the triangularity dependence of the kink response from GPEC and that of a related study using MARS-F [2]. The linear resistive MHD stability properties of the non-axisymmetric tokamak equilibria are assessed using CASTOR3D. Further, we use singular value decomposition techniques to assess the dependence of the response on shaping, focusing on changes in dominant mode harmonics. A comprehensive multi-modal analysis across the parameter space is used to identify primary factors influencing the response. This knowledge plays a pivotal role in optimizing plasma configurations and control strategies.

[1] Paz-Soldan C. et al, Nucl. Fusion 59 056012 (2019). 

[2] S. Gu et al, Nucl. Fusion 62 076031 (2022).