Multi-physics modeling of the long-term evolution of helium plasma exposed surfaces

Lasa, A.; Canik, J.; Blondel, Sophie; Younkin, Timothy; Curreli, Davide; Drobny, Jon; Roth, Philip C.; Cianciosa, M.; Elwasif, Wael; Green, D L; Wirth, Brian D.

doi:10.1088/1402-4896/ab4c29

Cited by 15 publications

(14 citation statements)

References 17 publications

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“…the long run sputtering causes erosion of the surface material. The amount of sputtering depends on a wide variety of factors, including surface material, surface roughness, plasma conditions and velocity distributions of particles striking the target (Cohen & Ryutov 1998b;Khaziev & Curreli 2015;Siddiqui et al 2016;Drobny et al 2017;Krasheninnikov & Kukushkin 2017;Lasa et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Large gyro-orbit model of ion velocity distribution in plasma near a wall in a grazing-angle magnetic field

Geraldini

2021

J. Plasma Phys.

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A model is presented for the ion distribution function in a plasma at a solid target with a magnetic field $\boldsymbol {B}$ inclined at a small angle, $\alpha \ll 1$ (in radians), to the target. Adiabatic electrons are assumed, requiring $\alpha \gg \sqrt {Zm_{e}/m_{i}}$ , where $m_{e}$ and $m_{i}$ are the electron and ion mass, respectively, and $Z$ is the charge state of the ion. An electric field $\boldsymbol {E}$ is present to repel electrons, and so the characteristic size of the electrostatic potential $\phi$ is set by the electron temperature $T_{e}$ , $e\phi \sim T_{e}$ , where $e$ is the proton charge. An asymptotic scale separation between the Debye length $\lambda _{D} = \sqrt {\epsilon _0 T_{{e}} / e^{2} n_{{e}} }$ , the ion sound gyro-radius $\rho _{s} = \sqrt { m_{i} ( ZT_{e} + T_{i} ) } / (ZeB)$ and the size of the collisional region $d_{c} = \alpha \lambda _{\textrm {mfp}}$ is assumed, $\lambda _{D} \ll \rho _{s} \ll d_{c}$ . Here $\epsilon _0$ is the permittivity of free space, $n_{e}$ is the electron density, $T_{i}$ is the ion temperature, $B= |\boldsymbol {B}|$ and $\lambda _{\textrm {mfp}}$ is the collisional mean free path of an ion. The form of the ion distribution function is assumed at distances $x$ from the wall such that $\rho _{s} \ll x \ll d_{c}$ , that is, collisions are not treated. A self-consistent solution of the electrostatic potential for $x \sim \rho _{s}$ is required to solve for the quasi-periodic ion trajectories and for the ion distribution function at the target. The large gyro-orbit model presented here allows to bypass the numerical solution of $\phi (x)$ and results in an analytical expression for the ion distribution function at the target. It assumes that $\tau =T_{i}/(ZT_{e})\gg 1$ , and ignores the electric force on the quasi-periodic ion trajectory until close to the target. For $\tau \gtrsim 1$ , the model provides an extremely fast approximation to energy–angle distributions of ions at the target. These can be used to make sputtering predictions.

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Section: Introductionmentioning

confidence: 99%

Large gyro-orbit model of ion velocity distribution in plasma near a wall in a grazing-angle magnetic field

Geraldini

2021

J. Plasma Phys.

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“…Then, a binary collision approximation (BCA) model and an impurity transport model are used to estimate the erosion and redeposition rates. The results presented in [48] suggest the presence of an erosion zone around the strike point (due to the He ions produced by the fusion reactions) and some of these sputtered W atoms are redeposited toward the private flux region. This erosion/redeposition may affect the retention calculated in this study, especially in the sub-surface region and the SSL.…”

Section: Impact Of the Sputtering/redeposition On The Hi Retentionmentioning

confidence: 86%

“…One can expect to have some fast ions that may sputter the W armor, though at a very low rate (3×10 −4 atoms per incoming ions according to [22]). To take into account this effect, one could use a similar workflow as described in [48] that gives a ionic temperature to a plasma sheath code to obtain the distribution of the ion energy on the wall. Then, a binary collision approximation (BCA) model and an impurity transport model are used to estimate the erosion and redeposition rates.…”

Section: Impact Of the Sputtering/redeposition On The Hi Retentionmentioning

confidence: 99%

“…Consequently, the contribution of the SSL to the total inventory (dashed line of figure 9) would disappear, knowing it is already low compared to the bulk HI inventory. For the plasma background calculated in [48], the net erosion flux is estimated to be of the order of 10 18 m −2 s −1 (0.1 monolayer per second). Taking this value as a first estimate and the thickness of 1 monolayer to be 1 AÅ, a plasma of 10 000 s would remove about 100 nm of material, removing completely the SSL.…”

Section: Impact Of the Sputtering/redeposition On The Hi Retentionmentioning

confidence: 99%

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Modelling of hydrogen isotopes trapping, diffusion and permeation in divertor monoblocks under ITER-like conditions

et al. 2021

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Distributed under a Creative Commons Attribution -NonCommercial -NoDerivatives| 4.0

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“…Additionally, those BCA codes that are available, through licensing agreements or as closed-source software, are not well suited to a wide range of physical problems. Particularly, the direct integration of BCA codes to particle or subsurface dynamics codes, such as those performed using F-TRIDYN for ITER divertor simulations (Lasa et al, 2020), requires costly external wrappers to manage simulations and process output files to perform file-based coupling. RustBCA, as part of the Plasma Surface Interactions 2 SciDAC Project suite of codes, has been developed to fill that gap and expand upon the feature set included in currently available BCA codes.…”

Section: Statement Of Needmentioning

confidence: 99%

RustBCA: A High-Performance Binary-Collision-Approximation Code for Ion-Material Interactions

Drobny¹,

Curreli²

2021

JOSS

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Ion-material interactions are of vital importance in industrial applications, the study and design of nuclear fusion devices, the engineering of survivable spacecraft components, and more. In particular, plasma-material interactions are typically dominated by ion-material interactions, including the phenomena of sputtering, reflection, and implantation. These phenomena are difficult to model analytically, and many such models rely on empirical or semi-empirical formulas, such as the Yamamura sputtering yield formula (Y. Yamamura, 1982), or the Thomas reflection coefficient (Thomas et al., 1992). However, such models are inherently limited, and of little applicability to complex geometry, multi-component surfaces, or for coupling to plasma or material dynamics codes. Since ion-material interactions span a range of energies from sub-eV to GeV and beyond, n-body approaches such as molecular dynamics can be computationally infeasible for many applications where the characteristic ion range exceeds the limits of reasonable molecular dynamics domains. Instead, approximations to the full n-body problem are used; the most common of these is the Binary Collision Approximation (BCA), a set of simplifying assumptions to the full n-body problem. RustBCA is a high-performance, general purpose, ion-material interactions BCA code, built for scientific flexibility and ease of use. RustBCA features include:

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Multi-physics modeling of the long-term evolution of helium plasma exposed surfaces

Cited by 15 publications

References 17 publications

Large gyro-orbit model of ion velocity distribution in plasma near a wall in a grazing-angle magnetic field

Large gyro-orbit model of ion velocity distribution in plasma near a wall in a grazing-angle magnetic field

Modelling of hydrogen isotopes trapping, diffusion and permeation in divertor monoblocks under ITER-like conditions

RustBCA: A High-Performance Binary-Collision-Approximation Code for Ion-Material Interactions

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