Control of hydrogen content and fuel recycling for long pulse high performance plasma operation in EAST

Yu, Y. W.; Hu, J. S.; Zuo, G. Z.; Sun, Z.; Wang, L.; Xu, W.; Wang, J. R.; Cao, B.; Gao, W.; Xu, J. C.; Li, J. G.

doi:10.1088/1741-4326/ab3ead

Title: Control of hydrogen content and fuel recycling for long pulse high performance plasma operation in EAST

Journal Article · 16 October 2019 · Nuclear Fusion

DOI: https://doi.org/10.1088/1741-4326/ab3ead · OSTI ID:1619199

Yu, Y. W. ^[1]; Hu, J. S. ^[2]; Zuo, G. Z. ^[1];

^[3]; Wang, L. ^[1]; Xu, W. ^[1]; Wang, J. R. ^[1]; Cao, B. ^[1]; Gao, W. ^[1]; Xu, J. C. ^[1]; Li, J. G. ^[1]

Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics
Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics; Univ. of Science and Technology of China, Hefei (China)
Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics; Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Control of fuel recycling and hydrogen content in the Experimental Advanced Superconducting Tokamak (EAST) using various methods is studied for high-power long pulse high confinement mode (H-mode) plasma operation. The results show that long duration first wall baking and discharge cleaning in EAST provides the necessary clean vacuum environment with a high ultimate vacuum of 3.6 × 10^-6 Pa and low outgassing rate of ~1.5 × 10^-4 Pa m³ s^-1 for plasma operation. In-vessel cryopumps are found to provide an efficient method for particle recycling control in the divertor region to decrease global recycling coefficient (R _global) from ~1.0 to ~0.8 during ohmic heating plasmas, and it provides a high particle exhausting rate of 10^20_10²¹ D-atoms s^-1 in high-power plasma operations. Long duration silicon coating is found to be more powerful than baking and discharge cleaning, which reduces the H/(H + D) ratio gradually to a value as low as 8%, and lithium coating is more effective and more efficient than silicon coating, to further reduce the H/(H + D) ratio to 3%. Real-time lithium powder injection is a novel method for recycling control, which reduces R global from 0.94 to 0.82 under lithium coating wall conditioning. By the combination and optimization of the above methods, H-mode plasmas with low hydrogen content and low fuel recycling have been achieved in EAST and have been extended gradually to 101 s in 2017. Recycling flux has even decreased gradually during 101 s H-mode plasmas due to increased first wall temperature and the resulting increased Li-II emission. These results provide valuable references on hydrogen content and fuel recycling control for long pulse H-mode plasmas of up to 400–1000 s with high-power heating in EAST and future fusion devices.

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Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Contributing Organization:: the EAST Team

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 1619199

Journal Information:: Nuclear Fusion, Vol. 59, Issue 12; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 21 works

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