Impurity Behavior in Plasma Recovery after a Vacuum Failure in the Experimental Advanced Superconducting Tokamak
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Published:2023-03-29
Issue:7
Volume:13
Page:4338
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ISSN:2076-3417
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Container-title:Applied Sciences
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language:en
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Short-container-title:Applied Sciences
Author:
Zhao Zihang12ORCID, Zhang Ling3, Zhou Ruijie3, Yang Yang12ORCID, Zhang Wenmin34, Cheng Yunxin34, Morita Shigeru5, Ti Ang3ORCID, Hu Ailan3, Sun Zhen3, Zhang Fengling34, Zhao Weikuan34, Li Zhengwei36, Cao Yiming36, Zuo Guizhong3, Liu Haiqing3
Affiliation:
1. Shanghai EBIT Laboratory, Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Institute of Modern Physics, Fudan University, Shanghai 200433, China 2. Department of Nuclear Science and Technology, Fudan University, Shanghai 200433, China 3. Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China 4. Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230031, China 5. National Institute for Fusion Science, Toki 509-5292, Gifu, Japan 6. Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China
Abstract
After a vacuum failure in a tokamak, plasma runaway or plasma disruptions frequently occur during plasma recovery, causing difficulties in rebuilding a well-confined collisional plasma. In this work, the impurity behavior during plasma recovery after a vacuum failure in the 2019 spring campaign of the Experimental Advanced Superconducting Tokamak (EAST) was studied by analyzing the spectra recorded by fast-time-response extreme ultraviolet (EUV) spectrometers with 5 ms/frame. During the plasma current ramp-up in recovery discharges, a high content of the low-Z impurities of oxygen and carbon was found, i.e., dozens of times higher than that of normal discharges, which may have caused the subsequent runaway discharges. The electron temperature in the recovery discharge may have dropped to less than 75 eV when the collisional plasma quenched to the runaway status, based on the observable impurity ions in the two cases. Therefore, the lifetime of collisional plasma in the recovery discharge, τc, was deduced from the lifetime of H- and He-like oxygen and carbon ions identified from EUV spectra. It was found that, after several discharges with real-time lithium granule injection, the runaway electron flux and O+ influx reduced to 45% and 20%, respectively. Meanwhile, the lifetime of confined plasma was extended from 113 ms to 588 ms, indicating the effective suppression of impurities and runaway electrons and improvement in plasma performance by real-time lithium granule injection. The results in this work provide valuable references for the achievement of first plasma in future superconducting fusion devices such as ITER and CFETR.
Funder
National Magnetic Confined Fusion (MCF) Energy Research & Development Program National Natural Science Foundation of China National Key Research & Development Project Youth Innovation Promotion Association of Chinese Academy of Sciences Chinese Academy of Sciences President’s International Fellowship Initiative
Subject
Fluid Flow and Transfer Processes,Computer Science Applications,Process Chemistry and Technology,General Engineering,Instrumentation,General Materials Science
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