Feedback Adaptive ELM Control towards (ITER) long pulse ELM suppression and its application to KSTAR*

Long pulse H-mode plasmas are typically conducive to the destabilization of Edge Localized Modes (ELMs), which can harm the fusion device beyond acceptable limits. Controlling these instabilities could prove crucial enabling economic fusion power. The objectives are to reduce the heat flux to the PFCs by suppressing ELMs through the application of 3D magnetic perturbations, while minimizing any performance degradation including  noninductive  fraction. To address this problem, a Feedback Adaptive ELM  controller has been designed, implemented and tested on KSTAR. During the ELM  suppressed phase, the controller adjusts 3D fields to reduce associated deleterious  effects. Interestingly, we have found that edge collisionality could play an important role in such feedback loops. In addition, a precursor detector has been developed which informs the controller if a loss of ELM suppression is imminent. The controller can pre-emptively adjust the 3D perturbations in an attempt to minimize the loss of ELM suppression. Using this controller, we have been able to achieve ELM-suppression while maximizing non-inductive fraction, which is vital for long-pulse. Recently, the controller has been demonstrated on long pulses at KSTAR, showing promising results.