Influence of the inverse sheath on divertor plasma performance in tokamak edge plasma simulations

Masline, Rebecca; Smirnov, R.D.; Krasheninnikov, S. I.

doi:10.1002/ctpp.201900097

Cited by 6 publications

(3 citation statements)

References 8 publications

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“…To address the issue of neutral density variation at the coreedge interface during the transition into the detached divertor regime we perform a series of the UEDGE simulations of edge plasma for DIII-D-like geometry and magnetic configuration (see [30] for details). Self-consistent modeling of plasma detachment in a high confinement mode (H-mode) of the operation of a tokamak and an impact of neutrals on anomalous cross-field plasma transport goes beyond the scope of this paper.…”

Section: Neutral Density At the Core-edge Interface During The Transi...mentioning

confidence: 99%

Neutral impact on anomalous edge plasma transport and its correlation with divertor plasma detachment

et al. 2020

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The impact of neutrals on anomalous edge plasma transport and zonal flow (ZF) is considered.As an example, it is assumed that edge plasma turbulence is driven by the resistive drift wave (RDW) instability. It is found that the actual effect of neutrals is not related to a suppression of the instability per se, but due to an impact on the ZF. Particularly, it is shown that, whereas the neutrals make very little impact on the linear growth rate of the RDW instability, they can largely reduce the zonal flow generation in the non-linear stage, which results in an enhancement of the overall anomalous plasma transport. Even though only RDW instability is considered, it seems that such an impact of neutrals on anomalous edge plasma transport, i.e. neutrals enhance the transport via the reduction of ZF, has a very generic feature. It is conceivable that such neutral induced enhancement of anomalous plasma transport is observed experimentally in a detached divertor regime, which is accompanied by a strong increase of neutral density.

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Section: Neutral Density At the Core-edge Interface During The Transi...mentioning

confidence: 99%

Neutral impact on anomalous edge plasma transport and its correlation with divertor plasma detachment

et al. 2020

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“…The study of sheaths is essential due to their increasing applications in various scenarios, such as plasmabased surface treatments [1,2], inductively coupled plasmas and electron cyclotron resonance plasmas [3] where magnetized sheaths could take place, probe diagnosis [4][5][6][7], boundary * Author to whom any correspondence should be addressed. plasma in fusion devices [8,9], etc. For electron-ion plasmas, the necessary condition for the existence of a steady-state sheath was first deduced by Bohm in 1949, often referred to as the Bohm criterion [10].…”

Section: Introductionmentioning

confidence: 99%

Properties of collisional plasma sheath with ionization source term and two-temperature electrons in an oblique magnetic field

Chen,

An,

Tan

et al. 2024

J. Phys. D: Appl. Phys.

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A collisional magnetized plasma sheath with two groups of electrons has been studied using a fluid model including the effects of the ionization source term and the collisional force between ions and neutral atoms. Two kinds of non-Maxwellian descriptions of electron velocity distribution, non-extensive distribution and truncated distribution, are applied in the model, and the ionization effects of both kinds are considered. By applying Sagdeev potential, the modified Bohm sheath criterion is derived. The effects of ionization, magnetic field, and high-temperature electron concentration ratio on plasma sheath density, potential, sheath thickness, and ion kinetic energy are studied. In cases with high background gas density, ion density accumulates at the sheath edge position, forming a peak and manifesting as a rapid drop in the potential profile. The distribution characteristics of electrons have a significant impact on the transport properties of ions. Oscillations and non-monotonic characteristics of net charge near the sheath edge occur as the magnetic field angle increases, leading to an increase in the sheath layer width. It can be seen that in the case of a collisional sheath structure with high-temperature electrons, it is essential to consider the sheath changes induced by the ionization and the collisional force. Compared to a symmetric electron velocity distribution, the actual thickness of the sheath layer in a truncated electron distribution assumption could be significantly reduced.

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“…The inverse sheath prevents the flow of cold ions to the electrode/wall surface which results in reduced sputtering at the target. The study of heat transmission in inverse sheath was started in [13] and the discussion on the mitigation of tokamak plasma surface interactions using thermionic divertor plates with inverse sheaths was presented in [14] with nice review of history related to electron emission in magnetic fusion devices. Although the plasma simulations are more helpful in understanding the plasma wall interaction problems but they are time consuming and resource dependent.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive kinetic theory of inverse sheath for a strong electron-emitting electrode in a low-pressure isotropic plasma

Din¹

2021

Phys. Scr.

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The basic kinetic theory of an electron emitting inverse sheath was presented in T Gyergyek, J Kovačič, I Gomez, J P Gunn, S Costea and M Mozetič (2020 Phys. of Plasmas 27, 023 520). Here we extend this theory to find the potential profile and kinetic energy flux in inverse sheath for floating and current carrying electron emitting electrode/wall. The values of emitted-electron temperature, number and current densities are explored for the existence and nonexistence of inverse sheath for floating and current carrying electrode/wall. For this we consider half Maxwellian velocity distribution functions of species (emitted-electron, plasma-electron and ions) at their respective emerging boundaries. The species charge densities are calculated self-consistently from the prior assumed positive sheath structure. The Poisson’s equation is then solved numerically for floating and current carrying electrode/wall with varying normalized emitted-electron and ion temperatures. The resulting inverse sheath solution is valid for limited range of emitted-electron and ion temperatures in case of floating electrode/wall. The kinetic energy flux relations for each species are derived in inverse sheath. The numerical solutions of these relations for floating and current carrying electrode/wall are presented for valid range of parameters. These solutions shows that the total or kinetic flux received by floating electrode/wall surface decreases with increasing of emitted-electron temperature and even approaches to zero for equal values of emitted-electron and plasma-electron temperatures.

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Influence of the inverse sheath on divertor plasma performance in tokamak edge plasma simulations

Cited by 6 publications

References 8 publications

Neutral impact on anomalous edge plasma transport and its correlation with divertor plasma detachment

Neutral impact on anomalous edge plasma transport and its correlation with divertor plasma detachment

Properties of collisional plasma sheath with ionization source term and two-temperature electrons in an oblique magnetic field

Comprehensive kinetic theory of inverse sheath for a strong electron-emitting electrode in a low-pressure isotropic plasma

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