Study on Time Delay of Impurity Line Emissions Between in the Edge and Core Plasmas in EAST Tokamak
YE Da-wei1, 2, DING Fang1*, LI Ke-dong1, 2, CHEN Xia-hua1, 2, LUO Yu1, 2, ZHANG Qing1, 2, MENG Ling-yi1, 2, LUO Guang-nan1, 2
1. Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
2. University of Science and Technology of China, Hefei 230026, China
Abstract：Impurity seeding is considered a promising method to enhance edge plasma radiation and mitigate the head load on the vessel surface in the future tokamak devices like ITER. However, part of the injected impurities would inevitably be transported to the plasma core, causing strong core radiation loss and degrading plasma confinement. Spectral observation is an important means to obtain the information on impurity species, concentration and distribution in tokamak which plays an important role in understanding the impurity transport in plasma. During the EAST (experimental advanced superconducting tokamak) diverter Ar seeding experiments, the diverter visible spectroscopy (Div-W) system and the fast-response extreme-ultraviolet (EUV) spectroscopy system is used to detect the line emission of Ar1+ (Ar Ⅱ at 401.36 nm) in the edge and monitor the line emission of Ar15+ (Ar ⅩⅥ at 35.39 nm）from plasma core, separately. Meanwhile, Ar Ⅱ and Ar ⅩⅥ intensities’ time evolution is obtained. The different ionization energies for Ar Ⅱ (27 eV) and Ar ⅩⅥ (918 eV) indicate that Ar Ⅱ and ArⅩⅥ are mainly distributed at the plasma boundary and the core plasma respectively. A correlation analysis method based on regular Pearson product moment has been developed to derive the time delay between the two line emissions from the edge and the core plasma. The relative delay time of Ar Ⅱ and Ar ⅩⅥ is calculated to characterize the transport time of Ar impurities from the boundary to the core. The results show that the rise of Ar ⅩⅥ line emission lags behind Ar Ⅱ line emission after Ar injection in the diverter. Moreover, the delay time is longer in the discharges with higher lower hybrid wave (LHW) heating power, indicating that higher LHW power can prolong the transport time of impurities from the boundary to the core.
Key words：Impurity seeding; Delay time; Correlation analysis; EAST tokamak
叶大为，丁 芳，李克栋，陈夏华，罗 宇，张 青，孟令义，罗广南. EAST边界和芯部杂质谱线的时间延迟研究[J]. 光谱学与光谱分析, 2022, 42(11): 3507-3511.
YE Da-wei, DING Fang, LI Ke-dong, CHEN Xia-hua, LUO Yu, ZHANG Qing, MENG Ling-yi, LUO Guang-nan. Study on Time Delay of Impurity Line Emissions Between in the Edge and Core Plasmas in EAST Tokamak. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(11): 3507-3511.
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