Impact of poloidal mode spectrum on 3D plasma response at various triangularities

In this work, we study the effects of the poloidal mode spectrum on 3D plasma response to externally applied magnetic perturbations (MPs) for DIII-D plasmas as a function of triangularity. There is growing evidence that 2D plasma shaping plays a critical role in determining the plasma response to the MPs, limiting access to the ELM suppression regime for cases of sufficiently high or low triangularity. Starting from kinetic EFIT reconstructions, the SEGWAY framework provides perturbed equilibria for varied triangularity which in turn implies both direct changes in the poloidal harmonic coupling and indirect changes of the plasma profiles. The GPEC code then provides the plasma response to various MPs configurations, including variations of the applied poloidal mode spectrum as well as the perturbation amplitude. In order to fully understand the dependence of the plasma response as triangularity changes, it is necessary to characterize both the kink and tearing components of the plasma response. GPEC enables direct analysis of the kink response through 3D edge displacement calculations and spectral composition, and provides insight into the tearing response through the rational currents and Chirikov parameters from the effective island widths associated with these currents.