Separatrix Shape of Field-Reversed Configurations

抄録

Near-infrared radiation from a field-reversed-configuration (FRC)plasma is observed during the stable phase using optical fibertubes. Internal structure of the FRC is estimated from an Abelinversion of the radiation intensities which are obtained from thevertical array of the fibers. It is confirmed that the structure has aconcaveform at the core region of the plasma column, as expected fromprevious FRC stud-ies. The axial array of the fibers shows that the separatrix boundaryis similar in shape to a racetrack when the FRC is long, extending tomirror regions of the confining field, and elliptical for a shortFRC. The equilibrium shape of the separatrix which is calculated usinga two-dimensional code also changes from elliptical to racetrack-likewith increase of the length in the mirror field, as observed in theexperiment.