A stationary long-pulse ELM-absent H-mode regime in EAST

作者：Ye, Y.; Xu, G. S.^*; Wan, B. N.; Chen, R.; Yan, N.; Guo, H. Y.; Shao, L. M.; Yang, Q. Q.; Wang, H. Q.; Zhang, W.; Xia, T. Y.; Zhang, T.; Li, Y. Y.; Wang, T. F.; Zang, Q.; Hu, Y. J.; Wu, G. J.; Zhang, L.; Hao, B. L.; Wang, L.; Li, Y. L.; Wu, X. Q.; Chen, L.; Lan, H.; Wang, Y. F.; Xu, J. C.; Hu, G. H.; Ding, S. Y.; Zhang, H.; Zhao, N.; Li, J.

来源：Nuclear Fusion, 2017, 57(8): 086041.

DOI：10.1088/1741-4326/aa7809

• ELM-absent
• ELM-free
• H-mode
• edge coherent mode
• high-energy confinement

A stationary edge-localized mode (ELM)-absent H-mode regime, with an electrostatic edge coherent mode (ECM) which resides in the pedestal region, has been achieved in the EAST tokamak recently. This regime allows the operation of a nearly fully noninductive long pulse (> 15 s), exhibiting a relatively high pedestal and good global energy confinement with H-98,H- y2 near 1.2, and excellent impurity control. Furthermore, this regime is mostly obtained with a 4.6 GHz lower hybrid current drive (LHCD) or counter-current neutral beam injection (NBI), plus electron cyclotron resonance heating, and an extensive lithium wall coating. This stationary ELM-absent H-mode regime transits to a stationary small ELM H-mode regime, and upon additional heating power from the 2.45 GHz LHCD, an ion cyclotron resonant frequency or co-current NBI is applied (under 4.6 GHz LHCD heating background). A slight change of the plasma configuration also makes the small ELMs reappear. The experimental observations suggest that a long-pulse ELM-absent regime can be induced by the ECM, which exhibits strong electrostatic fluctuations and may provide a channel for continuous particle (especially impurities) and heat exhaust across the pedestal. The ECM exists in the collisionality of nu(e) (*)= 2.5-4 and the pressure gradient |del P| = | dP/d(rho)| = 100-200 (kPa), which is in good agreement with the previous simulation of GYRO. This ELM-absent H-mode regime with ECM may offer a suitable candidate for high-performance, steady-state H-mode operation in future fusion reactors.

• 出版日期2017-8
• 单位中国科学院; 中国科学技术大学