PLASMA SURFACE INTERACTIONS IN THE ZT-40M REVERSED-FIELD PINCH

Wall conditioning has been used in ZT-40M to significantly modify the plasma-wall interactions. Both discharge cleaning and carbonization have resulted in plasmas with lower Z//e//f//f, lower resistive anomaly factor and lower concentrations of metallic impurities. This sensitivity of the discharge characteristics to wall conditions clearly indicates the need for a wider range of conditioning options in the next generation RFPs. Both PDC and GDC will be employed at elevated vessel temperatures (150-300 degree C). If possible, the temperature of the plasma-interactive surfaces will be adjustable ( less than equivalent to 300 degree C) so that wall conditions can be varied over a wider range for both the cleaning operations and plasma discharges. Finally, the inherently high energy density of RFPs results in the potential for high heat fluxes on the first-wall or limiter structures, or both. It will be necessary to ensure that this heat flux is distributed appropriately on the plasma-interactive surfaces.