Fast Imaging of Turbulent Modes in Linear Argon RF Plasma

Auburn Experiment for Instability Studies (ALEXIS) is a linear, magnetized plasma device that is known to exhibit both distinct instability modes as well as broadband turbulence. Recent studies in ALEXIS have positively and negatively biased a co-linear, cylindrical electrode (“can” electrode) to change the potential structure of the plasma column. The application of bias has been shown to modify the axial density profile and can induce a significant axial density gradient – measured both in-situ with probe diagnostics, and ex-situ with optical emission spectroscopy. We seek to further characterize the effect of this electrode biasing through the use of high-speed imaging. A high-speed digital camera was used to record an axial cross-section of the plasma column to identify the emergence and evolution of various instability modes and broadband turbulence. This presentation will provide initial observations of plasma modes observed at greater than 50000 frames per second as a function of bias voltage on the can electrode.