The erosion of tungsten divertor on EAST during neon impurity seeding in different divertor operation regimes

Zhao, Xuele; Sang, Chaofeng; Zhou, Qingrui; Zhang, Chen; Zhang, Yanjie; Ding, Rui; Ding, Fang; Wang, Dezhen

doi:10.1088/1361-6587/ab831b

Cited by 21 publications

(23 citation statements)

References 48 publications

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“…The experiments reveal that the evolution of both the W sputtering rate and yield at the divertor target can be the competing results between two seeding effects, increasing divertor Ne impurity content and decreasing electron temperature, which is consistent with the simulation results. [4] In addition, ELM suppression has been observed in this Ne seeding experiment. Due to the W sputtering by seeded Ne impurities, both the W and Ne impurities in the core plasma significantly increase after Ne seeding in the upper divertor.…”

Section: Introductionsupporting

confidence: 55%

“…[1] The existing simulation results reveal that the insufficient seeded Ne impurity could reduce the heat flux to the target, but the erosion of the W target can be obviously enhanced. [4] When the detached condition is achieved with sufficient Ne seeding, the W target erosion is obviously suppressed. In this work, the behaviors of W sputtering with Ne seeding in the divertor are experimentally observed and analyzed on EAST.…”

Section: Introductionmentioning

confidence: 99%

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Experimental investigation on divertor tungsten sputtering with neon seeding in ELMy H-mode plasma in EAST tokamak

Ye¹,

Ding²,

Li³

et al. 2022

Chinese Phys. B

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Neon (Ne) seeding is used to cool the edge plasma by radiation to protect the divertor tungsten (W) target in the Experimental Advanced Superconducting Tokamak (EAST). The W sputtering in the outer divertor target with Ne seeding is assessed by the divertor visible spectroscopy system. It is observed that the W sputtering flux initially increases with Ne concentration in the divertor despite the decreasing plasma temperature. After reaching a maximum around 25 eV, the W sputtering rate starts to decrease, presenting a suppression effect. The effect on the divertor W sputtering flux and yield due to the competition between the increase of the Ne concentration and the decrease of the plasma temperature is discussed. The results show that enough Ne seeding is essential to effectively reduce the electron temperature and thus to suppress W sputtering. Moreover, ELM suppression is observed when Ne and W impurities enter the core plasma, which could be correlated to the enhanced turbulence transport in the pedestal.

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Section: Introductionsupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Experimental investigation on divertor tungsten sputtering with neon seeding in ELMy H-mode plasma in EAST tokamak

Ye¹,

Ding²,

Li³

et al. 2022

Chinese Phys. B

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“…The creation, transport and core accumulation of W impurity are the key issues for the application of W as the PFM. In this work, the production of W impurities is calculated by the erosion of W target via empirical physical sputtering yield formula [49], and the details can be found in references [8,38]. With the calculated W source and plasma background provided by SOLPS modeling, the transport of W impurity is simulated by DIVIMP code [50], which uses the Monte Carlo method to track particles and their charge states in the plasma.…”

Section: Simulation Modelmentioning

confidence: 99%

“…Since W impurity is not included by the present SOLPS modeling, we first simulate pure deuterium discharge OSP raises from ∼1.0 MW m −2 to ∼17.8 MW m −2 , exceeding the tolerance of W target, i.e. (1) T et should be below 44 eV, assuming D + accelerated through a sheath drop of 3kT e with an impact energy of ∼5kT e [55] and the sputtering threshold for D + incident into W of 220 eV [38];…”

Section: Tungsten Divertor With Argon Seedingmentioning

confidence: 99%

“…Impurity control can be achieved by optimum gas puffing and divertor pumping, and by the optimization of divertor geometry for impurity shielding [37]. Apart from reducing plasma temperature in front of target, the seeded impurity can also dominate the W target sputtering [38], which influences the lifetime of the device and the contamination of the core plasma. Therefore, the W target erosion and W impurity transport are very crucial for the designed divertor and the assessment should be implemented.…”

Section: Introductionmentioning

confidence: 99%

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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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Modeling of tungsten divertor target erosion induced by impurity during edge‐localized modes by using a kinetic model

Wang,

Sang,

Liu

et al. 2024

Contrib. Plasma Phys

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The burst of edge‐localized modes (ELMs) leads to an increase in the energy and particle fluxes to the divertor target. Tungsten (W) is chosen as the primary candidate material for plasma‐facing components (PFCs) in the future fusion devices, and EAST has already upgraded all divertors to use W. Therefore, understanding tungsten target erosion during ELMs and finding the correlation between erosion rate and key ELM parameters are crucial for steady‐state operation. In this work, based on the Vlasov–Poisson model (VPM), we develop a one‐dimensional kinetic parallel transport code to investigate the parallel transport of particles in the EAST device during ELMs and the resulting target erosion. The EAST experiment (#102182) is simulated by VPM code. The simulation results are compared with experimental data as well as free‐stream model (FSM) calculation, showing the accuracy of the code. Considering the presence of lithium (Li) impurities in EAST discharge, the erosion of the W target is simulated. The results indicate that during the burst of ELM, the total average tungsten erosion rate, , is determined by both deuterium (D) and Li ions. D ions dominate the erosion when the ELM frequency (fELM) is low (ranging from 50 to 175 Hz), while Li impurities become more important than D+ in high‐frequency ELMs (fELM > 175 Hz). As fELM increases, the time‐averaged erosion of the W target first increases and then decreases. Therefore, the reduction of W erosion benefits from high‐frequency ELMs, with impurity ions being the primary contributor to the erosion.

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The erosion of tungsten divertor on EAST during neon impurity seeding in different divertor operation regimes

Cited by 21 publications

References 48 publications

Experimental investigation on divertor tungsten sputtering with neon seeding in ELMy H-mode plasma in EAST tokamak

Experimental investigation on divertor tungsten sputtering with neon seeding in ELMy H-mode plasma in EAST tokamak

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

Modeling of tungsten divertor target erosion induced by impurity during edge‐localized modes by using a kinetic model

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