Density compensation with pellet fueling during ELM suppression with n = 4 RMP on metal-wall EAST tokamak

• A full density compensation has been achieved by pellet fueling during ELM suppression with n = 4 RMPs. • ELM suppression is terminated and small ELMs reappear during pellet injection. • The amplitude of sawtooth crash decreases and high frequency small sawtooth crashes appear during the pellet fueling. Pellet injection is the most promising fueling method to achieve a deep particle deposition for future fusion reactors. On metal-wall EAST tokamak, a full density compensation has been achieved by the pellet fueling during ELM suppression with n = 4 RMP which will be used in ITER’s operation. During the pellet injection, ELM suppression is terminated and small ELMs reappear. The plasma stored energy does not have a reduction with the pellet injection. Meanwhile, large sawtooth accompanied with RMP application is modified by the pellet injection. The amplitude of sawtooth crash decreases and high frequency small sawtooth crashes appear during the pellet fueling. The concentration of heavy impurities in the plasma core, such as tungsten and molybdenum, has an obvious reduction with the ELM reappearance and sawtooth modification. Although the same ELM behaviors also appears after divertor gas fueling, pellet fueling can modify the core plasma more significantly. All these experimental results will provide a good support to the ITER operation in the future.