Investigating the effect of biasing of a hollow cylindrical electrode in the ALEXIS plasma device

The Auburn Linear Experiment for Instability Studies (ALEXIS) is a 2m long, 10 cm diameter, inductively coupled, rf, linear plasma device that is designed to study a variety of plasma instabilities and waves. Recent studies in ALEXIS have shown that electrical biasing of a cylindrical electrode placed near the downstream end has led to dramatic changes in the local plasma light emission for certain plasma conditions and electrode bias voltages. Plasma measurements made in the "dark" regions for low RF power input (< 40 W) and large negative bias voltages (< - 60V) show that the electron density decreased by over an order of magnitude when compared to measurements made with no bias voltage applied to the cylindrical electrode. This presentation will show preliminary results from both fast-imaging measurements and optical emission spectroscopy to characterize the physics behind the decrease in light emission.