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 × ITER-89P L–mode scaling have been obtained with a radiated power fraction above 70%. When the outer separatrix strike point was positioned for pumping with the DIII–D cryopump, ELMing H–mode (Type III 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. IMPURITY FEEDBACK CONTROL FOR ENHANCED DIVERTOR AND EDGE G.L. Jackson, et al. RADIATION IN DIII–D DISCHARGES GENERAL ATOMICS REPORT GA–A22345 1