Investigation Of Hhfw And Nbi Combined Heating In Nstx

A series of experiments was conducted to investigate the combined utilization of HHFW and NBI auxiliary heating in NSTX plasmas. A modest increase of the total stored energy coincident with a near doubling of the neutron production rate is observed when NBI beating is added to HHFW in L-mode plasmas. An increase in the core electron temperature is also observed. On the other hand, essentially no stored energy augmentation nor neutron production rate enhancement is observed when applying HHFW during the "H" phase of NBI driven H-mode plasmas. Spectroscopic measurements of the edge carbon line radiation indicate an unpredicted ion temperature increase, suggesting that edge effects are reducing the amount of HHFW power reaching the plasma core.