7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Recent progress on high-Z impurity diagnostics development andtungsten transport study on EAST Tokamak
ZHANG Ling1, CHENG Yunxin1, HU Ailan1, MORITA Shigeru2, ZHANG Wenmin3,1,
ZHANG Fengling3,1, MITNIK Darío4,1, LI Zhengwei5,1, ZHOU Chenxi1, ZHOU Zhen3,1,CAO Yiming5,1, MA Jiuyang3,1, XU Zhehao5,1, XU Lang3,1, LIU Haiqing1
1
Institute of Plasma Physics, Chinese Academy of Sciences
2
National Institute for Fusion Science, Toki, Japan3University of Science and Technology of China, Hefei, China
4
Instituto de Astronomía y Física del Espacio, Argentina
5Anhui University, Hefei, China
E-mail (speaker): zhangling@ipp.ac.cn
Impurities play an essential role in maintaining
high-performance plasmas in magnetic confinement
fusion research because the radiation power loss andbulk ion dilution caused by the impurity ions quickly
degrade the plasma performance. It is well known thatradiation loss quickly increases with the atomic numberof the impurity element. In International Thermonuclear
Experimental Reactor (ITER), on the other hand,
tungsten is used as the divertor material instead ofcarbon. Upper and lower graphite divertors inExperimental Advanced Superconducting Tokamak(EAST) were replaced by tungsten divertors in 2014 and2021, respectively, to improve plasma performance inlong pulse discharges and accumulate knowledge on thetungsten divertor operation. Studies on the tungsten
behavior in edge and core plasmas are crucial forenhancing plasma performance. For this purpose, acomplete set of tungsten spectroscopy diagnostic systems
has been developed and installed on EAST tokamak,
which consists of a visible (VIS) spectroscopy system,fast-time-response, and space-resolved extreme
ultraviolet (EUV) spectroscopy systems.
Fast-time-response EUV spectroscopy system
includes four grazing-incidence flat-field spectrometersdeveloped on EAST since 2014 [1][2]. One is working at
5-138 Å, and the other three are working at 20-500 Å.
EUV spectra with high spectral resolution at the fullrange of 5-500 Å could be observed simultaneously ineach discharge at a sampling rate of 5 ms/frame.
Hundreds of emission lines from tungsten ions W4+-W45+
have been carefully identified from the EUV spectra as afundamental work [3]. Moreover, a database of EUVlines from multiple impurity elements in fusion plasma
has been preliminarily built [4][5]. Space-resolved EUV
spectroscopy system also includes four spectrometers,
which have been installed successively since 2017. Twoof them working at 5-138 Å provide the tungsten line
intensity profiles in ρ≤0.3 with 15-50 ms/frame, and theother two working at 30-520 Å provide that in ρ≤0.7
with 50-200 ms/frame [6][7]. Quantitative analysis oftungsten concentration and impurity ion density profiles
are then performed using the EUV spectroscopy for thetungsten transport study [8]. Additionally, since 2021
VIS spectroscopy system with two optics andspectrometers has been developed successfully [9]. One
is designed for an adjustable 2D profile measurement oftungsten sputtering in the upper divertor. The other is forthe total radial profile measurement of Zeff and M1
transition from tungsten ions of W8+-W28+.
Benefiting from the high-performance impurity
diagnostics studies on tungsten transport and its control
have been widely carried out in EAST combined withexperiment and simulation, e. g. the effect of electron
cyclotron resonance heating (ECRH) and lower hybrid
wave (LHW) heating on tungsten transport, impurity
transport behavior at plasma edge with application ofresonance magnetic perturbation (RMP) coils, and theeffect of plasma rotation on up-down asymmetry
distribution of tungsten ions. The preliminary results will
be introduced in the talk.
References[1] L. Zhang Rev. Sci. Instrum. 86 (2015)123509[2] Z. Xu Nucl. Instrum. Meth. A1010 (2021) 165545[3] W.M. Zhang 43th ITPA Diagnostic meeting (2023)[4] L Li Plasma Sci. Technol. 23 (2021) 075102[5] W.M. Zhang Phys. Scr. 97 (2022) 045604[6] L. Zhang Nucl. Instrum. Meth. A 916 (2019) 169[7] Y.X. Cheng Rev. Sci. Instrum. 93 (2022)123501[8] Y.X. Cheng IEEE T Plasma Sci 50 (2022) 691-699[9] A.L Hu 43th ITPA Diagnostic meeting (2023)
Acknowledgment
National Key Research and Development Program ofChina (2022YFE03180400, 2019YFE030403,
2018YFE0311100, 2018YFE0303104, and2022YFE03020004), National Natural Science
Foundation of China (Grant Nos. 12322512, 11905146,11975273, and 12075283), Chinese Academy ofSciences President’s International Fellowship Initiative(PIFI) (Grant No. 2020VMA0001) and the Alliance ofInternational Science Organizations (ANSO) Visiting
Fellowship (ANSO-VF-2021-03).