Experimental study of detachment density threshold in L-mode plasmas on EAST

Meng, Lingyi; Liu, Jianbin; Xu, Jichan; Wang, Liang; Xu, G. S.; Guo, H.Y.; Liu, Xiaoju; Si, H.; Wang, H Q; Ge, Wendi; Lan, H.; Chen, Liang; Qian, Xinyuan; Zhang, Jiayuan; Feng, Wei; Yang, Qingquan; Long, Fei; Li, Kedong; Gao, Puze; Tao, Yuqiang; Luo, Yu; Li, Ang; Yu, Lingfei; Gao, Shanlu; Yuan, Q.P.; Ding, Fang; Yu, Yaowei; Duan, Yanmin; Zhang, Bin; Gao, Wei

doi:10.1088/1361-6587/ab877f

Cited by 17 publications

(12 citation statements)

References 51 publications

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“…The detachment onset density is n OMP,onset e,sep = 2.1 × 10 19 m −3 , 1.6 × 10 19 m −3 , 1.9 × 10 19 m −3 , respectively, for cases figures 2(a)-(c), showing Horiz-near case can promote the occurrence of plasma detachment. This is in agreement with recent EAST experiment observation [53].…”

Section: Design Of the Geometry Of East Lower Divertorsupporting

confidence: 94%

Design of EAST lower divertor by considering target erosion and tungsten ion transport during the external impurity seeding

Sang

Zhou

et al. 2021

Nucl. Fusion

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To demonstrate the performance of tungsten (W) as the divertor target material and to solve the power handling problem during high power long-pulse discharge, the upgrade of EAST lower divertor is planned. In this work, the physical design of the W divertor is presented by using 2D edge plasma code SOLPS and Monte Carlo impurity transport code DIVIMP. The optimized divertor geometry is proposed after systematic examination of target shapes, target slant angles and the pump opening locations. The performance of the designed divertor is further assessed by impurity seeding. By comparing the medium and high power discharges with argon (Ar) seeding, the differences on the divertor power radiation and impurity core accumulation are distinguished. The simulated effective ion charge Z eff fits well the scaling law, which is based on multi-machine database. Ar seeding and neon (Ne) seeding scans are carried out separately. The simulation results indicate Ar has higher power radiation efficiency than that of Ne, thus promoting the achievement of plasma detachment. However, the core compatibility with Ar is worse than with Ne. The W target erosion and W impurity transport during impurity seeding are simulated by the DIVIMP–SOLPS coupled modeling. It illustrates that under the similar divertor plasma conditions, Ar seeding causes more serious W erosion and more severe core contamination by W impurity, than Ne seeding. Finally, the divertor in–out asymmetry is studied by considering electromagnetic drifts. The simulation results manifest that the designed open vertical inner target reduces in–out asymmetry due to that its weak power radiation capability is offset by the ion flow driven by the drifts. In addition, the designed divertor is compatible with the quasi snowflake magnetic configuration. These studies will improve the understanding of W target sputtering and W impurity transport control during the radiative divertor discharges for CFETR/DEMO.

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Section: Design Of the Geometry Of East Lower Divertorsupporting

confidence: 94%

Design of EAST lower divertor by considering target erosion and tungsten ion transport during the external impurity seeding

Sang

Zhou

et al. 2021

Nucl. Fusion

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“…In addition, the T e profiles near the magnetic strike point with a DPD structure are lower than those without a DPD structure; as shown in figure 18(e), the T e even decreases to less than 5 eV in the inner divertor target case, indicating divertor detachment. It is well known that there is a lower detachment threshold in the inner divertor region than in the outer divertor region [13,45,46]; however, the DPD appears much more easily at the inner divertor target plate in a favorable B t discharge with the same heating power and plasma density platform. In the case of a low T e near the inner divertor target in EAST, a strong radial electric field may mainly be induced by the radial V f profile near the divertor target.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of double-peaked particle deposition at divertor target plates in the EAST tokamak

Wang

et al. 2021

Nucl. Fusion

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Increasing the heat and particle deposition on the divertor target plates is an effective approach for reducing the extremely high heat load. Future tokamak fusion devices are expected to have a deposition width on the order of a millimeter. Recently, a double-peaked distribution (DPD) pattern of particle deposition at the divertor target plates has been observed in both deuterium and helium plasma discharges in the Experimental Advanced Superconducting Tokamak, which can significantly spread the deposition width of heat and particle fluxes, and clearly shows a toroidal symmetric distribution. It has been found that the DPD behavior occurs not only in plasma discharges with lower hybrid wave (LHW) heating, but also with electron cyclotron resonance heating or neutral beam injection (NBI) heating alone. In addition, the DPD shows an obvious in–out asymmetry between the divertor target plates, which strongly depends on the toroidal field direction, i.e. it distinctly appears on the outer divertor plate in unfavorable B t conditions, while shifting to the inner divertor plate under favorable B t conditions. Meanwhile, the transition between the single-peaked distribution and the DPD is normally correlated with the line-averaged plasma density and the auxiliary heating power. The statistical results for the pure LHW heating discharge scheme show that the DPD behavior is significantly affected by both the plasma density and the heating power, i.e. the lower the ratio of the plasma density to the heating power, the more likely it is that DPD behavior will occur. The critical boundary lines between the DPD and non-DPD patterns are obtained with the line expressions ∼ 2P LHW,abs + 1.4 and ∼ 3.33P LHW,abs + 1 for the unfavorable and favorable B t cases, respectively. Finally, the underlying physics is also discussed, suggesting that the electric field drifts and the local sheath boundary condition may exert a strong influence on the DPD.

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“…Recently, active control of detachment or radiation compatible with core plasma performance has advanced significantly, 53 , 54 , 55 with a series of active feedback control modules successfully developed and implemented. These modules have excellent compatibility with high core plasma performance, which has also been demonstrated on Doublet III D (DIII-D) in 2019.…”

Section: The East Project and Related Activitiesmentioning

confidence: 99%

Recent progress in Chinese fusion research based on superconducting tokamak configuration

et al. 2022

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Experimental study of detachment density threshold in L-mode plasmas on EAST

Cited by 17 publications

References 51 publications

Design of EAST lower divertor by considering target erosion and tungsten ion transport during the external impurity seeding

Design of EAST lower divertor by considering target erosion and tungsten ion transport during the external impurity seeding

Characteristics of double-peaked particle deposition at divertor target plates in the EAST tokamak

Recent progress in Chinese fusion research based on superconducting tokamak configuration

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