Structure and Dynamics of Disruptive Kink Instabilities Measured by Fast Videography and Magnetics in HBT-EP

Measurements of kink instabilities, resonant magnetic perturbations (RMPs), and disruptions in the High Beta Tokamak-Extended Pulse (HBT-EP) are studied using toroidal and poloidal arrays of magnetic field sensors\footnote{Levesque, \textit{et al.}, \textit{Nuc Fus}, \textbf{57}, 086035 (2017).} and fast videography\footnote{Angelini, \textit{et al.}, \textit{Plasma Phys Contr Fus}, \textbf{57}, 045008 (2015).}. The fast camera (Phantom v7.3) is most sensitive to light from the plasma edge and detects the structure of the plasma boundary for all types of MHD activity. Large helical ``plumes'' and ``bubbles'' are detected during disruptions (when helical perturbations can exceed 20\%\ of the equilibrium poloidal field) and during kink mode precursors (when the mode amplitude can exceed 5\%\ of the equilibrium field.) We present videos of the distorted plasma boundary and compare high-speed videos with computations of the helical boundary based on magnetic measurements. A variety of disruptions show ``plume''/``bubble'' structures reach 5~cm (or 30\%\ of the plasma minor radius) from the plasma edge. The distortion and dynamics of the plasma boundary are discussed in relation to on-going investigations of scrape-off layer (SOL) currents during kink instabilities and disruptions.