ELM elimination with Li powder injection in EAST discharges using the tungsten upper divertor

Maingi, R.; Hu, Jiansheng; Sun, Zhuo; Tritz, K.; Zuo, Guizhong; Xu, Wei; Huang, Ming; Meng, X.C.; Canik, J.; Diallo, A.; Lunsford, R.; Mansfield, D. K.; Osborne, T.H.; Gong, Xiaojing; Wang, Y.F.; Li, Y. Y.; Team, East

doi:10.1088/1741-4326/aa9e3f

Cited by 50 publications

(40 citation statements)

References 45 publications

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“…In the following we briefly discuss the various terms considered in Eqs. (1)(2)(3)(4), namely the forces, currents, particles and heat fluxes on the dust grain. The expressions for these quantities, taken mainly from Refs.…”

Section: Numerical Modelmentioning

confidence: 99%

“…The dust grain has an initial velocity directed downwards, v 0 = v 0 e z , with v 0 = −10 m/s. This scenario mimics impurity powder injection experiments [3,4,5,6]. The chosen poloidal position maximizes the dwelling of the dust grains into the plasma, while ensuring that the trajectory is contained in the SOL and does not cross the LCFS, where the turbulence characteristics are qualitatively different from the SOL.…”

Section: Example Of Dust Grain Trajectorymentioning

confidence: 99%

“…Dust particles can also be a source of tritium retention for a fusion reactor, and its in vessel inventory must be limited for the nuclear safety of the facility. Recently, impurity injection in the form of sub-millimeter powder grains has also been used for wall conditioning and plasma control purposes in both tokamaks [3,4,5] and stellarators [6,7]. Furthermore, the injection of (sub)millimeter-sized fragments of material with the Shattered Pellet Injection is proposed as a disruption mitigation mechanisms for ITER [8].…”

Section: Introductionmentioning

confidence: 99%

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Hyperdiffusion of dust particles in a turbulent tokamak plasma

et al. 2021

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The effect of plasma turbulence on the trajectories of dust particles is investigated for the first time. The dynamics of dust particles is computed using the ad-hoc developed Dust Injection Simulator code, using a 3D turbulent plasma background computed with the TOKAM3X code. As a result, the evolution of the particle trajectories is governed by the ion drag force, and the shape of the trajectory is set by the Stokes number St ∝ a d /n 0 , with a d the dust radius and n 0 the density at the separatrix. The plasma turbulence is observed to scatter the dust particles, exhibiting a hyperdiffusive regime in all cases. The amplitude of the turbulent spread of the trajectories ∆r 2 is shown to depend on the ratio Ku/St, with Ku ∝ u rms the Kubo number and u rms the fluctuation level of the plasma flow. These results are compared with a simple analytical model, predicting ∆r 2 ∝ (Ku/St) 2 t 3 , or ∆r 2 ∝ (u rms n 0 /a d ) 2 t 3 . As the dust is heated by the plasma fluxes, thermionic emission sets the dust charge, originally negative, to slightly positive values. This results in a substantial reduction of the ion drag force through the suppression of its Coulomb scattering component. The dust grain inertia is then no longer negligible, and drives the transition from a hyperdiffusive regime towards a ballistic one.

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Section: Numerical Modelmentioning

confidence: 99%

Section: Example Of Dust Grain Trajectorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hyperdiffusion of dust particles in a turbulent tokamak plasma

et al. 2021

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“…As another Li wall conditioning method, the real-time Li aerosol injection technique is also developed on EAST and actively supports the achievement of long-pulse ELMfree H modes [26,27]. The edge impurity levels and particle recycling can be reduced by real-time Li injection, thus improving plasma performances.…”

Section: Control Of W Sputtering Sourcementioning

confidence: 99%

Plasma–tungsten interactions in experimental advanced superconducting tokamak (EAST)

et al. 2019

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Tungsten (W) is used as the armor material of the International Thermonuclear Experimental Reactor (ITER) divertor and is regarded as the potential first wall material of future fusion reactors. One of the key challenges for the successful application of W in fusion devices is effective control of W at an extremely low concentration in plasma. Understanding and control of W erosion are not only a prerequisite for W impurity control, but also vital concerns to plasma-facing component (PFC) lifetime. Since the application of ITER-like water-cooled full W divertor in EAST in 2014, great efforts were made to investigate W erosion by experiment and simulation. A spectroscopic system was developed to provide a real-time measurement of W sputtering source. Both experiment and simulation results indicate that carbon (C) is the dominant impurity causing W sputtering in L-mode plasmas, which comes from the erosion of C plasma-facing material (PFM) in the lower divertor and the main chamber limiters. The mixture layer on the surface of W PFCs formed through redeposition or the wall coating can effectively suppress W erosion. Increasing the plasma density and radiation can reduce incident ion energy, thus alleviating W sputtering. In H-mode plasmas, control of edge localized mode (ELM) via resonant magnetic perturbation (RMP) proves to be capable of suppressing intra-ELM W erosion. The experiences and lessons from the EAST W divertor are beneficial to the design, manufacturing and operation of ITER and beyond.

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“…More recently, the injection of low-Z solid materials in powder, dust or small granule form was introduced as a novel technique for various real-time applications. First applications focused on disruption mitigation, real-time wall conditioning, mitigation of edge localized modes (ELMs), and confinement improvement with boron, boron nitride (BN), and lithium powders at T-10, DIII-D, EAST, ASDEX Upgrade, KSTAR, LHD, and W7-X [24,25,26,27,28,29,30,31,32].…”

Section: Introductionmentioning

confidence: 99%

Mitigation of plasma-wall interactions with low-Z powders in DIII-D high confinement plasmas

Effenberg,

Bortolon,

Casali

et al. 2022

Preprint

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Experiments with low-Z powder injection in DIII-D high confinement discharges demonstrated increased divertor dissipation and detachment while maintaining good core energy confinement. Lithium (Li), boron (B), and boron nitride (BN) powders were injected in H-mode plasmas (Ip =1 MA, Bt =2 T, P NB =6 MW, ne = 3.6 − 5.0 • 10 19 m −3 ) into the upper small-angle slot (SAS) divertor for 2-s intervals at constant rates of 3-204 mg/s.The multi-species BN powders at a rate of 54 mg/s showed the most substantial increase in divertor neutral compression by more than an order of magnitude and lasting detachment with minor degradation of the stored magnetic energy W mhd by 5%. Rates of 204 mg/s of boron nitride powder further reduce ELM-fluxes on the divertor but also cause a drop in confinement performance by 24% due to the onset of an n = 2 tearing mode.The application of powders also showed a substantial improvement of wall conditions manifesting in reduced wall fueling source and intrinsic carbon and oxygen content in response to the cumulative injection of non-recycling materials.The results suggest that low-Z powder injection, including mixed element compounds, is a promising new core-edge compatible technique that simultaneously enables divertor detachment and improves wall conditions during high confinement operation.

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ELM elimination with Li powder injection in EAST discharges using the tungsten upper divertor

Cited by 50 publications

References 45 publications

Hyperdiffusion of dust particles in a turbulent tokamak plasma

Hyperdiffusion of dust particles in a turbulent tokamak plasma

Plasma–tungsten interactions in experimental advanced superconducting tokamak (EAST)

Mitigation of plasma-wall interactions with low-Z powders in DIII-D high confinement plasmas

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