RMP ELM Control in Dimensional and Dimensionless Matched Hydrogen Plasmas*

We report on the latest attempts to achieve suppression of edge-localized modes (ELMs) via the application of resonant magnetic perturbations (RMPs) in hydrogen plasmas by matching the pedestal to those of ELM suppressed deuterium plasmas with respect to either dimensional or dimensionless parameters. Most studies investigating RMP ELM suppression have focused on deuterium plasmas. Despite meeting the known deuterium access criteria, ELM suppression has not been achieved in hydrogen. 2D peeling-ballooning stability calculations would suggest RMP ELM suppression to be present especially in the dimensionless match. In addition, the strength of the applied total (vacuum + plasma response) RMP compares favorably in terms of ideal islands widths and their overlap as well as the criterion of having a resonant flux surface overlapping with region of zero or little ExB rotation at the pedestal top. One possibly crucial difference between the hydrogen and deuterium plasmas with RMPs is the significant reduction of turbulence in the pedestal region in hydrogen as compared to deuterium. This is in line with previous observations from ASDEX Upgrade. Overall, these results challenge our understanding of RMP ELM suppression further and make predictions towards its applicability in future devices more uncertain as well as motivating the investigation of the stabilizing effect of turbulence on ELMs.