Studies of Compatibility of ELM suppression via Resonant Magnetic Perturbations with electron heating and impurity seeding at DIII-D

In experiments at DIII-D, a feedback control scheme was developed during low collisionality RMP ELM suppression using argon gas to control the core radiation. The next step fusion device ITER will be equipped with a set of Resonant Magnetic Perturbation (RMP) coils which have been demonstrated to completely suppress Edge-Localized Modes (ELMs) in many existing tokamaks. In order to be relevant for ITER, the RMP ELM suppression scenario needs to be able to operate at ITER-like dominant electron wave heating and be compatible with at least partial divertor detachment. A maximum core radiation fraction of about 70% was achieved via argon puffing while ELMs were still suppressed. Increasing the radiation further led to a transition back into L-mode, as opposed to a return of an ELMing or ELM-free H-mode. Bolometry measurements show that the power is radiated mostly inside the mid-radius. Langmuir probe data show a significant reduction of the parallel heat fluxes onto the divertor target and a reduction of the target temperature suggesting approach to detachment onset. However, partial or complete detachment was not reached in this low-density scenario. Scans of the ratio of applied electron cyclotron resonance to neutral beam injection heating power have been observed to lead to a loss of ELM suppression related to modified conditions at the pedestal top. These results show progress and highlight issues on the road to qualify RMP ELM suppression as a suitable scenario for ITER.