Wall conditioning and ELM mitigation with boron nitride powder injection in KSTAR

Gilson, Erik; Lee, H. H.; Bortolon, A.; Choe, Wonho; Diallo, A.; Hong, Suk–Ho; Lee, J.; Maingi, R.; Mansfield, D.K.; Nagy, A.; Park, S. H.; Song, In‐Hyuck; Song, J. H.; Yun, Sang‐Won; Yoon, S.W.; Nazikian, R.

doi:10.1016/j.nme.2021.101043

Cited by 19 publications

(20 citation statements)

References 15 publications

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“…While IPDs have previously been installed and operated on other metal-walled tokamaks such as AUG [14,15] and EAST [16,17], the long pulse capabilities and full-W environment make WEST an excellent test bed to extend the evaluation of the IPD as a real-time wall conditioning technique. The present results can additionally be compared with powder injection experiments in carbon-walled machines, namely DIII-D [18], KSTAR [19], W7-X [20], and LHD [21,22].…”

Section: Introductionmentioning

confidence: 93%

“…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%

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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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Section: Introductionmentioning

confidence: 93%

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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“…A general advantage compared to gas injection is that certain impurities can be delivered in pure form (no dilution through additional hydrogen bonding, as in the case of methane or diborane) and are not toxic or explosive. Recent studies at EAST and KSTAR show promising results regarding real-time wall conditioning in long pulse scenarios [46,27].…”

Section: Discussionmentioning

confidence: 99%

“…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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“…(iv) The clouds of ablated material can significantly alter plasma-grain interactions by "shielding" the dust particle and mitigating the incoming heat flux. Such shielding effects are of particular importance for relatively large grain size Brown et al 2014) [similar effects are observed in the course of the injection of large pellets in fusion plasmas for both fueling and discharge termination (Parks et al 1977;Rozhansky and Senichenkov 2005)] and for the case where a large amount of powder particles is injected into fusion plasma for both an active impact on edge plasma parameters and in-situ conditioning of the first wall (Mansfield et al 2010;Osborne et al 2015;Lunsford et al , 2021Sun et al 2019;Bortolon et al 2019aGilson et al 2021). (v) One of the main dust sources in fusion devices with carbon-based PFC is delamination of the co-deposited layers formed on PFCs due to erosion processes (Federici et al 2001;Rubel et al 2001;Sharpe et al 2002;Winter 2004;.…”

Section: Introductionmentioning

confidence: 93%

Dust and powder in fusion plasmas: recent developments in theory, modeling, and experiments

Ratynskaia

Bortolon

Krasheninnikov

2022

Rev. Mod. Plasma Phys.

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In this paper, we present a brief historic overview of the research on dust in fusion devices with carbon plasma-facing components and then highlight the most recent developments in the post-carbon era of the field. In particular, we consider how the metallic dust form, mobilize, and interact with fusion plasmas and plasma facing components. Achievements in wall conditioning and associated anomalous plasma transport modification, including ELM suppression, with the powder injection technique is another focus of the paper. Capabilities of the state-of-art simulation tools to describe different aspects of dust in fusion devices are exemplified and new directions for future dust studies are brought forward.

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Wall conditioning and ELM mitigation with boron nitride powder injection in KSTAR

Cited by 19 publications

References 15 publications

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

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

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

Dust and powder in fusion plasmas: recent developments in theory, modeling, and experiments

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