Surface roughness effects on plasma near a divertor plate and local impact angle

Hu, Wanpeng; Dai, Shuyu; Kirschner, A.; Wang, Dezhen

doi:10.1016/j.nme.2016.09.016

Cited by 11 publications

(3 citation statements)

References 35 publications

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“…sheath-tracing evaluated sputtering yields, or not. In literature, it was shown that micrometric roughness can have an important influence in deflecting impinging ions towards orthogonal incidence [43], which corresponds to the simulation with sheath-tracing evaluated sputtering yields. However, this seems not to be the case for the nanometric roughness of the c-W sample (see table 4), which would be commonly neglected in the evaluation of the deflection towards the surface, as occurs in the simulation without sheath-tracing.…”

Section: Discussionmentioning

confidence: 86%

ERO2.0 modelling of nanoscale surface morphology evolution

Alberti¹,

Sala²,

Romazanov³

et al. 2021

Nucl. Fusion

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Plasma–material interaction (PMI) in tokamaks determines the life-time of first-wall (FW) components. Due to PMI, FW materials are eroded and transported within the device. Erosion is strongly influenced by the original morphology of the component, due to particle redeposition on near surface structures and to the changing of impact angle distributions, which results in an alteration of the sputtering effects. The Monte-Carlo impurity transport code ERO2.0 is capable of modelling the erosion of non-trivial surface morphologies due to plasma irradiation. The surface morphology module was validated against experimental data with satisfactory agreement. In this work, we further progress in the validation of the ERO2.0 capabilities by modelling both numerically generated surfaces as well as real surfaces, generated using atomic force microscopy (AFM) measurements of reference tungsten samples. The former are used to validate ERO2.0 against one of the morphology evolution models present in literature, in order to outline the conditions for reliable code solutions. Modifications induced in AFM-generated surfaces after argon and helium plasma irradiation are compared, showing a similar post-exposure morphology, mostly dominated by surface smoothing. Finally, the ERO2.0 morphology retrieved after He plasma exposure is compared to experimentally-available scanning electron microscopy and AFM measurements of the same surface morphology exposed in the linear plasma device GyM, showing the need for further improvements of the code, while a good agreement between experimental and simulated erosion rate is observed.

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Section: Discussionmentioning

confidence: 86%

ERO2.0 modelling of nanoscale surface morphology evolution

Alberti¹,

Sala²,

Romazanov³

et al. 2021

Nucl. Fusion

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“…Additionally, the results shown in this paper are important for understanding the sheath formation above nonflat or nonsmooth surfaces in laboratory plasmas, for example, rough surfaces caused by the built‐ups from the erosion and redeposition of wall materials in fusion devices (Hu et al, ) or substrate surfaces under plasma etching processes (Kawamura et al, ).…”

Section: Discussionmentioning

confidence: 88%

Plasma Sheath Formation at Craters on Airless Bodies

2019

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The surfaces of airless planetary bodies directly interact with the solar wind plasma and ultraviolet radiation, resulting in surface charging and formation of a sheath above the surface. These interactions are further complicated by the presence of craters with characteristic sizes spanning over orders of magnitude from centimeters to kilometers. Here we present laboratory results to show that the plasma sheath formed in a crater varies significantly, depending on the radius of the crater compared to the Debye length of ambient plasma. When the Debye length is much smaller than the radius of the crater, the plasma expands into the crater and forms a sheath along the crater wall and floor. When the Debye length is comparable to or larger than the radius of the crater, the potential in the crater becomes more homogenous with a largely reduced electric field. A double layer is formed between the crater and ambient plasma. It is likely that the electrons slowed down by the sheath cannot be efficiently reflected back to the plasma due to the reduced electric field and pile up within the crater, causing an increased electron density that crosses over the density of the ions.

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“…Surface roughness can lead to modification of the sheath properties, the local impact angle and thus also the average physical sputtering yields [47][48][49]. Typical arithmetic mean roughness values R a for solid PFCs exceed few micrometers [50].…”

Section: Role Of Surface Roughnessmentioning

confidence: 99%

On thermionic emission from plasma-facing components in tokamak-relevant conditions

Komm

Ratynskaia

Tolias

et al. 2017

Plasma Phys. Control. Fusion

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The first results of particle-in-cell simulations of the electrostatic sheath and magnetic pre-sheath of thermionically emitting planar tungsten surfaces in fusion plasmas are presented. Plasma conditions during edge localized modes (ELMs) and during inter-ELM periods have been considered for various inclinations of the magnetic field and for selected surface temperatures. All runs have been performed under two assumptions for the sheath potential drop; fixed or floating. The primary focus lies on the evaluation of the escaping thermionic current and the quantification of the suppression due to the combined effects of space-charge and Larmor gyration. When applicable, the results are compared with the predictions of analytical models. The heat balance in the presence of thermionic emission as well as the contribution of the escaping thermionic current to surface cooling are also investigated. Regimes are identified where emission needs to be considered in the energy budget.

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Surface roughness effects on plasma near a divertor plate and local impact angle

Cited by 11 publications

References 35 publications

ERO2.0 modelling of nanoscale surface morphology evolution

ERO2.0 modelling of nanoscale surface morphology evolution

Plasma Sheath Formation at Craters on Airless Bodies

On thermionic emission from plasma-facing components in tokamak-relevant conditions

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