Shear Flow Stabilization of Turbulence in the Helimak

The Helimak is a good approximation to the infinite cylindrical slab, but the end plates allow application of radial electric fields that drive radial currents. A strong bifurcation occurs at a critical bias condition with reduction in the level of fractional density fluctuations, generally with both smaller fluctuations and higher density. The bifurcation occurs for both positive and negative bias voltages at a threshold current. The nature of the stabilization and the dependence of the threshold condition on plasma parameters will be described. Work supported by the Department of Energy Office of Fusion Energy Sciences DE-FG03-00ER54609.