Scientists Achieve Low Recycling No-ELM H-mode Regime in EAST

Chinese scientists of the Institute of Plasma Physics under Hefei Institutes of Physical Sciencehas made new progress in the research of EAST low-recycling no-ELM high-confinement mode operation.

This work was done by XU Guosheng and his team and waspublished in Nuclear Fusion.

A highly reproducible spontaneous no-ELM regime was achieved in the EAST superconducting tokamak with the extensive lithium wall coating or real-time lithium powder/granules injection.

Unlike the previously published high-recycling strong electrostatic edge coherent mode (ECM) dominated no-ELM operation [Y. Ye, G.S. Xu, et al 2017 Nuclear Fusion 57 086041], this regime exhibited a clear low-density dependence and was less correlated with the pedestal turbulence. The energy confinement enhancement factor  could be up to 1 and it was compatible with the fully non-inductive operation.

Diagnostic data and ELITE/NIMROD simulations indicated that the low pedestal foot density and the ion diamagnetic stability effect may play a key role in the achievement of this regime. The low pedestal foot density might have a strong ion diamagnetic stabilizing effect, which could stabilize the medium-n and high-n Peeling-Ballooning modes.

In this regime, the recycling neutral particles from the wall surface were significantly reduced, and the pedestal fueling effect was weakened, which had a commonality with the expected high heating power, low pedestal fueling effect on the future reactors. Therefore, the development of this research provided a useful reference for the control of ELMs on future fusion experimental devices.

This research is strongly supported by the EAST team and LI Jiangang academician workstation of Shenzhen University, and is funded by the National Natural Science Foundation of China and the National Magnetic Confinement Fusion Science Program of China. (YE Yang reports)

Article related links: https://doi.org/10.1088/1741-4326/ab2806

Time evolution diagram of typical parameters in low-recycling no-ELM regime in EAST (Image by YE Yang)