Enhanced Confinement with Plasma Biasing in the MST Reversed Field Pinch

We report an increase in particle confinement with plasma biasing in a reversed field pinch. Miniature plasma sources are used as electrodes to negatively bias the plasma at the edge $(r/a\sim 0.9)$. Particle content increases and ${\mathrm{H}}_{\alpha }$ radiation decreases upon application of bias and global particle confinement roughly doubles as a result. Energy confinement is not significantly affected by biasing the edge. Measurements of plasma potential, impurity flow, and floating potential fluctuations indicate that strong flows are produced and that electrostatic fluctuations are reduced.