Suppression of edge localized modes with real-time boron injection using the tungsten divertor in EAST

Sun, Zhuo; Diallo, A.; Maingi, R.; Qian, Yi; Tritz, K.; Wang, Y.F.; Bortolon, A.; Nagy, A.; Zhang, L.; Duan, You; Ye, Yudong; Zhao, Hailin; Wang, H.Q.; Gu, Xiaoxia; Zuo, Guizhong; Xu, Wei; Huang, Ming; Li, C.L.; Meng, X.C.; Zhou, C.; Liu, H.Q.; Zang, Qing; Wang, Li; Qian, J.; Xu, G. S.; Gong, X.Z.; Hu, Jiansheng; Team, East

doi:10.1088/1741-4326/abc763

Cited by 40 publications

(44 citation statements)

References 36 publications

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“…It reduces wall recycling and impurity content, which allows the plasma performances to be improved by accessing lower plasma collisionalities, similarly to the case of glow discharge boronization. Furthermore, as these experiments have been mainly performed in H-mode plasmas, the IPD has revealed itself an effective tool for suppression of edge-localized modes, allowing access to an H-mode free of these violent bursts 11 . Nevertheless, a widespread turbulence reduction and temperature increase like the one reported in this Article has not been previously observed in the powder injection experiments performed on tokamaks, or following a glow discharge boronization.…”

Section: Impurity Powder Injection Experimentsmentioning

confidence: 99%

Observation of a reduced-turbulence regime with boron powder injection in a stellarator

et al. 2022

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In state-of-the-art stellarators, turbulence is a major cause of the degradation of plasma confinement. To maximize confinement, which eventually determines the amount of nuclear fusion reactions, turbulent transport needs to be reduced. Here we report the observation of a confinement regime in a stellarator plasma that is characterized by increased confinement and reduced turbulent fluctuations. The transition to this regime is driven by the injection of submillimetric boron powder grains into the plasma. With the line-averaged electron density being kept constant, we observe a substantial increase of stored energy and electron and ion temperatures. At the same time, the amplitude of the plasma turbulent fluctuations is halved. While lower frequency fluctuations are damped, higher frequency modes in the range between 100 and 200 kHz are excited. We have observed this regime for different heating schemes, namely with both electron and ion cyclotron resonant radio frequencies and neutral beams, for both directions of the magnetic field and both hydrogen and deuterium plasmas.

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Section: Impurity Powder Injection Experimentsmentioning

confidence: 99%

Observation of a reduced-turbulence regime with boron powder injection in a stellarator

et al. 2022

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“…Higher drop rates resulted in abrupt disruptions, most likely due to rapid increases in the electron density and radiated power. IPD experiments on other tokamaks and stellarators have sustained drop rates of > 17 mg/s, however these experiments typically utilized increased auxiliary power and/or different magnetic configurations [14,16,19,21]. The number of B atoms injected per shot varied from 2.7×10 20 to 4.0×10 21 atoms depending upon the drop rate and drop duration.…”

Section: Ipd Experiments On Westmentioning

confidence: 99%

Initial results from boron powder injection experiments in WEST lower single null L-mode plasmas

Bodner¹,

Gallo²,

Diallo³

et al. 2022

Nucl. Fusion

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Using a recently installed impurity powder dropper (IPD), boron powder (< 150 μm) was injected into lower single null (LSN) L-mode discharges in WEST. IPDs possibly enable real-time wall conditioning of the plasma-facing components and may help to facilitate H-mode access in the full-tungsten environment of WEST. The discharges in this experiment featured Ip = 0.5 MA, BT = 3.7 T, q95 = 4.3, tpulse = 12–30 s, ne,0 ~ 4×1019 m-2, and PLHCD ~ 4.5 MW. Estimates of the deuterium and impurity particle fluxes, derived from a combination of visible spectroscopy measurements and their corresponding S/XB coefficients, showed decreases of ~ 50% in O+, N+, and C+ populations during powder injection and a moderate reduction of these low-Z impurities (~ 50%) and W (~ 10%) in the discharges that followed powder injection. Along with the improved wall conditions, WEST discharges with B powder injection observed improved confinement, as the stored energy WMHD, neutron rate, and electron temperature Te increased significantly (10–25% for WMHD and 60–200% for the neutron rate) at constant input power. These increases in confinement scale up with the powder drop rate and are likely due to the suppression of ion temperature gradient (ITG) turbulence from changes in Zeff and/or modifications to the electron density profile.

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“…This technique has been shown to improve wall conditioning already in tokamaks [4,5,6,7], reducing wall recycling and impurity content, and in general increasing the plasma performances by accessing lower plasma collisionalities. Furthermore, the IPD has revealed itself an effective tool for ELMs suppression, allowing the access ELM-free H-mode [8]. A similar powder injection technique has been recently employed on the W7-X stellarator, showing an improvement of confinement [9], most likely induced by the modification of the plasma profiles and in a change of the radial electric field.…”

Section: Motivationmentioning

confidence: 99%

Observation of a novel reduced-turbulence regime with boron powder injection in a stellarator

Nespoli¹,

Masuzaki²,

Tanaka³

et al. 2021

Preprint

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We report the first observation of a novel confinement regime in a stellarator plasma, characterized by increased confinement and reduced turbulent fluctuations. The transition to this new regime is driven by the injection of sub-millimetric boron powder grains into the plasma. With the line averaged electron density being kept constant, substantial increase of stored energy, electron and ion temperature have been observed. At the same time, the amplitude of the plasma turbulent fluctuations is halved. While lower frequency fluctuations are damped, higher frequency modes in the range 100 ≤ f [kHz] ≤ 200 are excited. The access to this regime has been observed for different heating schemes, namely with both electron and ion cyclotron resonant radio frequency, and neutral beams, for both directions of the magnetic field, and for both hydrogen and deuterium plasmas.

show abstract

Suppression of edge localized modes with real-time boron injection using the tungsten divertor in EAST

Cited by 40 publications

References 36 publications

Observation of a reduced-turbulence regime with boron powder injection in a stellarator

Observation of a reduced-turbulence regime with boron powder injection in a stellarator

Initial results from boron powder injection experiments in WEST lower single null L-mode plasmas

Observation of a novel reduced-turbulence regime with boron powder injection in a stellarator

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