Scientists YU Yaowei and Vacuum and Plasma Surface Interactions group with Institute of Plasma Physics under Hefei Institutes of Physical Science conducted a series of studies on fuel recycling and hydrogen content control during the recent experiments on EAST through which they obtained new discoveries for high-power long pulse high confinement mode (or H-mode) plasma operation.
Fuel recycling and hydrogen content control has always been the key focus in H-mode plasma operation. To address the key issue, the team conducted several studies on conventional methods for wall conditioning and their impact on fuel recycling and hydrogen content.
They found in-vessel cryopumps decreased global recycling coefficient from ~1.0 to ~0.8, and it provided a high particle exhausting rate of 1020-1021 D atoms/s.
Long duration silicon coating and lithium coating were obviously better than that of conventional methods such as baking and discharge cleaning. In particular, the lithium coating could reduce the H/(H+D) ratio to 3%. Real-time lithium powder injection is a novel method for recycling control, which reduced global recycling coefficient from 0.94 to 0.82 under lithium coating wall conditioning.
The combination of above various methods could reduce the hydrogen content and fuel recycle coefficient for achieving 101s H-mode plasma discharge.
These results may provide valuable references on hydrogen content and fuel recycling control for long pulse H-mode plasma of up to 400–1000s with high-power heating in EAST and future fusion devices.
The research was supported by the EAST team and was funded by National Natural Science Foundation and the National Key R&D Program.
Fuel recycling control of EAST long pulse H-mode plasma (Image by WANG Junru)
Effect of plasma position control on fuel recycling control (Image by WANG Junru)
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