Impacts of impurity flux on erosion and deposition of carbon/tungsten rough surfaces

Dai, Shuyu; Yang, K.R.; Liu, D.H.; Shi, Quan; Cui, Bo; Liu, S.G.; Wang, D.Z.

doi:10.1016/j.nme.2020.100802

Cited by 4 publications

(3 citation statements)

References 28 publications

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“…On the contrary, C deposition on plasma-facing component (PFC) surfaces reduces the effective sputtering rate of Mo and W due to deposited C diluting the material surface in L-mode DIII-D discharges [6]. Similar calculation results of W erosion suppression were reported for L-mode EAST discharges when the C impurity concentration was higher than 1% [7,8]. Hence, the characteristics of those low-Z impurities such as deposition rate, concentration in the plasma, and incident angle and energy comprise crucial information needed to understand the net erosion of PFCs.…”

Section: Introductionsupporting

confidence: 56%

Micro-trench measurements of the net deposition of carbon impurity ions in the DIII-D divertor and the resulting suppression of surface erosion

Abe¹,

Skinner²,

Bykov³

et al. 2021

Phys. Scr.

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We report carbon impurity ion incident angles and deposition rates, along with silicon erosion rates, from measurements of micro-engineered trenches on a silicon surface exposed to L-mode deuterium plasmas at the DIII-D divertor. Post exposure ex-situ analysis determined elemental maps and concentrations, carbon deposition thicknesses, and erosion of silicon surfaces. Carbon deposition profiles on the trench floor showed carbon ion shadowing that was consistent with ERO calculations of average carbon ion angle distributions (IADs) for both polar and azimuthal angles. Measured silicon net erosion rates negatively correlated with the deposited carbon concentration at different locations. Differential erosion of surfaces on two different ion-downstream trench slope structures suggested that carbon deposition rate is affected by the carbon ion incident angle and significantly suppressed the surface erosion. The results suggest the C impurity ion incident angles, determined by the IADs and surface morphology, strongly affect erosion rates as well as the main ion (D, T, He) incident angles.

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Section: Introductionsupporting

confidence: 56%

Micro-trench measurements of the net deposition of carbon impurity ions in the DIII-D divertor and the resulting suppression of surface erosion

Abe¹,

Skinner²,

Bykov³

et al. 2021

Phys. Scr.

View full text Add to dashboard Cite

show abstract

“…The sputtering yield is highly sensitive to ion incident angles θ > 70 • -80 • [10,11], where θ is an angle from the surface normal, and hence, the incident angle and energy of ions impacting the PFC surface can dominantly affect the PFC erosion lifetime. Both polar and azimuthal ion incident angles are also a critical factor to understand the erosion mechanism of rough surfaces (nm-μm) [12][13][14][15][16][17] and mechanical gaps (μm-mm) of PFCs [18,19]. Furthermore, the wide sheath potential structure significantly impacts the prompt re-deposition of high-Z species (W and Mo) as well because sputtered heavy impurities are ionized and accelerated in the wide sheath fields, which have a comparable scale length with the ion gyro radius [20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Determination of the characteristic magnetic pre-sheath length at divertor surfaces using micro-engineered targets on DiMES at DIII-D

Abe¹,

Skinner²,

Bykov³

et al. 2022

Nucl. Fusion

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The magnetic pre-sheath (MPS) width, L MPS, is a critical parameter to define the sheath potential, which controls the ion trajectory of low-Z species (D, T, He, and C), as well as the prompt re-deposition of high-Z species. To determine L MPS, we fabricated micro-trenches (30×30×4 µm) via focused ion beam (FIB) milling on a silicon surface and exposed them to L-mode deuterium plasmas in DIII-D via the Divertor Material Evaluation System (DiMES) removable sample exposure probe. The areal distribution of impurity depositions, mainly consisting of carbon, was measured by energy-dispersive X-ray spectroscopy (EDS) to reveal the deuterium ion shadowing effect on the trench floors. The carbon deposition profiles showed that the erosion was maximized for the azimuthal direction of φ = -40° (referenced to the toroidal magnetic field direction) as well as the polar angle of θ = 80°. A Monte Carlo equation-of-motion model, based on a collisionless MPS, was used to calculate the azimuthal and polar deuterium ion angle distributions (IADs) for a range of L MPS = k × ρ i, where ρ i is the ion gyro radius and k = 0.5-4. Then, gross erosion profiles were calculated by a Monte Carlo micro-patterning and roughness (MPR) code for ion sputtering using as input the calculated azimuthal and polar IADs for each value of k. Good agreement with the experimental C deposition profiles was obtained for the case k = 2.5-3.5. This result is consistent with a previous kinetic modeling prediction of k ~ 3, as well as previous analytical investigations that predicted the L MPS to be several ion gyro radii. A validation of theoretical sheath models supports its applicability to ITER and pilot plant divertors to successfully predict plasma-materials interactions.

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“…In this work, the impacts of porous nanostructure on the net physical sputtering have been investigated by the PISCES-A experiments [25] and SURO-FUZZ modelling [21,[26][27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Nonlinear impact of the porous nanostructure on the net tungsten erosion in the linear plasma device PISCES-A

Yang¹,

Dai²,

Doerner³

et al. 2022

Nucl. Fusion

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The tungsten fuzz growth under non-erosive and erosive helium plasmas in the linear plasma device PISCES-A has been investigated by experiments and simulations. The simulation results benchmarked against the experimental measurements indicate a decayed net physical sputtering yield during fuzz growth under the erosive helium plasma. Further, a nonlinear dependence of the net tungsten erosion on the ‘effective’ porous nanostructure that can be sputtered by incident helium particles has been found.

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Impacts of impurity flux on erosion and deposition of carbon/tungsten rough surfaces

Cited by 4 publications

References 28 publications

Micro-trench measurements of the net deposition of carbon impurity ions in the DIII-D divertor and the resulting suppression of surface erosion

Micro-trench measurements of the net deposition of carbon impurity ions in the DIII-D divertor and the resulting suppression of surface erosion

Determination of the characteristic magnetic pre-sheath length at divertor surfaces using micro-engineered targets on DiMES at DIII-D

Nonlinear impact of the porous nanostructure on the net tungsten erosion in the linear plasma device PISCES-A

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