Ion Flow Measurement on the C-2W Open Field Line Plasma

Accurate operation and high performance of the open field line plasma surrounding the Field Reversed Configuration (FRC) is crucial to achieving the goals of successful temperature ramp up and confinement improvement on C-2W. Of particular importance is the control of the end loss plasma flow from the FRC core towards the divertor plates and mitigation of the flow of impurities back into the FRC plasma. A high-resolution Doppler spectrometer was used to measure impurity ion flow in both directions at different locations across the open field line plasma from a position in the mirror region between the central FRC confinement vessel and the inner divertor. Impurity ion velocity profiles are presented for various experimental conditions.