Soft-x-ray emission, plasma equilibrium, and fluctuation studies on Madison Symmetric Torus

A miniature multichord soft-x-ray detection system has been installed on the Madison Symmetric Torus (MST) reversed-field pinch to study the plasma equilibrium and fluctuation properties of standard- and improved-confinement discharges. Because of the relatively flat MST density and temperature profiles, the spatial resolution is relatively poor along the line of sight. However, the system can resolve line-integrated-emissivity fluctuations which are strongly correlated with the rotating m=1 global magnetic fluctuations as well as heat pulse propagation with edge-resonant m=0 bursts during improved-confinement discharges. Abel inversion based on Park's inversion techniques indicates peaking of the equilibrium emissivity profile following sawtooth events during standard discharges and profile flattening after m=0 bursts during improved-confinement discharges.