Wide-window ELM suppression on DIII-D: predicting the SVR operational space for optimized edge plasma response and experimental validation

A recently validated integrated modeling framework that uses only 0D parameters and a reference boundary to synthetically construct equilibria and evaluate the resonant field response to 3D fields was used to scan the Shape and Volume Rise (SVR) operational space. The SVR upgrade on DIII-D enables highly elongated, triangular plasmas with pedestals approaching pilot-plant targets. The predictive modeling objective was to identify achievable SVR subspaces exhibiting optimal edge plasma coupling and response to n=3 resonant magnetic perturbations (RMPs). The model predicted a broad plateau of robust odd-parity coupling for q₉₅​≳4.2. Below this threshold, the response is predicted to rapidly decay and cross over to even-parity dominance. ELM suppression in the strongly shaped SVR plasma (dRsep≤1cm), which has historically proven elusive, was first demonstrated at high performance (β_n≈2.5). Remarkably, complete ELM suppression was maintained in odd-parity over q_95​=4.1−5.3, an exceptionally wide ELM suppression window that is in close agreement with the model-predicted plateau. Below q₉₅​≈4.1, ELMs re-appeared, consistent with the predicted weaking of the odd-parity response. Experimental validation of 3D spectrum features reinforces confidence in predictive optimization tools and enables more deliberate tailoring of 3D fields for unrealized plasmas.