Type-I ELM mitigation by continuous lithium granule gravitational injection into the upper tungsten divertor in EAST

Sun, Zhen ; Yuzhong, Qian; Maingi, Rajesh ; Wang, Yifeng; Wang, Yumin; Nagy, Alexander ; Tritz, Kevin; Lunsford, Robert ; Gilson, Erik ; Zuo, Guizhong; Xu, Wei; Huang, Ming; Meng, Xiancai; Mansfield, Dennis K. ; Zang, Qing; Zhu, Xiang; Lin, Xin; Liu, Haiqing; Duan, Yanmin; Zhang, Ling; Lyu, Bo; Liu, Yong; Wang, Liang; Bortolon, Alessandro ; Xu, Guosheng; Gong, Xianzu; Hu, Jiansheng
Issue date: 2021
Cite as:
Sun, Zhen, Yuzhong, Qian, Maingi, Rajesh, Wang, Yifeng, Wang, Yumin, Nagy, Alexander, Tritz, Kevin, Lunsford, Robert, Gilson, Erik, Zuo, Guizhong, Xu, Wei, Huang, Ming, Meng, Xiancai, Mansfield, Dennis K., Zang, Qing, Zhu, Xiang, Lin, Xin, Liu, Haiqing, Duan, Yanmin, Zhang, Ling, Lyu, Bo, Liu, Yong, Wang, Liang, Bortolon, Alessandro, Xu, Guosheng, Gong, Xianzu, & Hu, Jiansheng. Type-I ELM mitigation by continuous lithium granule gravitational injection into the upper tungsten divertor in EAST [Data set]. Princeton Plasma Physics Laboratory, Princeton University. https://doi.org/10.11578/1814955
  author      = {Sun, Zhen and
                Yuzhong, Qian and
                Maingi, Rajesh and
                Wang, Yifeng and
                Wang, Yumin and
                Nagy, Alexander and
                Tritz, Kevin and
                Lunsford, Robert and
                Gilson, Erik and
                Zuo, Guizhong and
                Xu, Wei and
                Huang, Ming and
                Meng, Xiancai and
                Mansfield, Dennis K. and
                Zang, Qing and
                Zhu, Xiang and
                Lin, Xin and
                Liu, Haiqing and
                Duan, Yanmin and
                Zhang, Ling and
                Lyu, Bo and
                Liu, Yong and
                Wang, Liang and
                Bortolon, Alessandro and
                Xu, Guosheng and
                Gong, Xianzu and
                Hu, Jiansheng},
  title       = {{Type-I ELM mitigation by continuous lith
                ium granule gravitational injection into
                 the upper tungsten divertor in EAST}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  url         = {https://doi.org/10.11578/1814955}

Large edge-localized modes (ELMs) were mitigated by gravitational injection of lithium granules into the upper X-point region of the EAST device with tungsten plasma-facing components. The maximum ELM size was reduced by ~ 70% in high βN H-mode plasmas. Large ELM stabilization was sustained for up to about 40 energy confinement times, with constant core radiated power and no evidence of high-Z or low-Z impurity accumulation. The lithium granules injection reduced the edge plasma pedestal density and temperature and their gradients, due to increased edge radiation and reduced recycling from the plasma-facing components. Ideal stability calculations using the ELITE code indicate that the stabilization of large ELMs correlates with improved stability of intermediate-n peeling-ballooning modes, due to reduced edge current resulting from the profile changes. The pedestal pressure reduction was partially offset by a core density increase, which resulted in a modest ~ 7% drop in core stored energy and normalized energy confinement time. We surmise that the remnant small ELMs are triggered by the penetration of multiple Li granules just past the separatrix, similar to small ELMs triggered by deuterium pellet [S. Futatani et al., Nucl. Fusion 54 (2014) 073008]. This study extends previous ELM elimination with Li powder injection [R. Maingi et al., Nucl. Fusion 58 (2018) 024003] in EAST because 1) use of small, dust-like powder and the related potential health hazards were eliminated, and 2) use of macroscopic granules should be more applicable to future devices, due to deeper penetration than dust particles, e.g. inside the separatrix with velocities ~ 10 m/s in EAST.

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