Imaging of Boundary Plasma Displacements During RMPs in DIII-D

Visible imaging is used to measure the boundary displacement due to n = 2 and n = 3 RMPs in H-mode plasmas in DIII-D. Displacements $\approx$2 cm on the outer midplane are measured in LSN H-modes using \break active imaging of Doppler shifted deuterium beam emission with n = 2 RMPs rotating in the co-current direction [1] where the kink response is expected to be maximized. In contrast, displacements due to static n = 3 RMPs are $\approx$4 mm in similar LSN H-modes, with no measurable change when the n = 3 RMP phase is ``flipped'' by 60$^{\circ}$ toroidally. Plasma shape is also found to have a strong effect on the plasma response: n = 3 RMPs in Double Null Divertor plasmas are $\approx$2 mm, 10x smaller than the displacements in similar LSN plasmas, consistent with magnetics measurements. We will compare boundary displacements measured with active beam emission and passive C III imaging to separatrix manifold displacements and kink response in plasma response models.\par \vskip6pt \noindent [1] R.A. Moyer, et al., Nucl. Fusion {\bf52} 123019 (2012)