HELIUM TRANSPORT AND EXHAUST STUDIES IN DIII-D

A better understanding of helium transport in the plasma core and edge in enhanced confinement regimes is now emerging from recent experimen tal studies on DIIID. Overall, the results are encouraging with signif icant helium exhaust obtained in a diverted, ELMing H-mode plasma, wit h tau(He)/tau(E) similar to 10 and transport studies E indicating tha t D-He/X(eff) similar to 1 in all plasma conditions studied to date. H owever, measurements in the core and pumping plenum show a significant dilution of helium as it flows from the plasma core to the pumping pl enum. Such dilution could be the limiting factor in the overall remova l rate of helium in a reactor system.