Impurity feedback control for enhanced divertor and edge radiation in DIII-D discharges

Radiated power fractions above 90% have been achieved in DIII-D using impurity feedback control. Heat flux reductions up to a factor of 6 and confinement enhancements of 1.6 x ITER-89P L-mode scaling have been obtained with a radiated power fraction above 90%. When the outer separatrix strike point was positioned for pumping with the DIII-D cryopump, ELMing H-mode (Type HI ELMs) was triggered with neon feedback injection in conjunction with a constant deuterium gas puff rate. Changes in the ELM frequency, energy confinement and central neon concentrations as a function of radiated power are presented. Observations of detached discharges with H-mode confinement similar to the ASDEX-U CDH-mode are also discussed.