Influence of secondary electron emission on plasma-surface interactions in the low earth orbit environment

Nuwal, Nakul; Levin, Deborah A.

doi:10.1088/1361-6595/abe7a1

Cited by 9 publications

(1 citation statement)

References 45 publications

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“…To satisfy the numerical validity of the time-explicit nature of the coupling between Poisson's equation and particle movement, we use a time-step, ∆t < 0.1ω −1 pe and grid cell-size, ∆x < λ D [21], where ω pe and λ D are the local electron plasma frequency and Debye length, respectively. The code CHAOS has previously been used in plume-plasma [2,3], and plasma-surface interaction [22] studies, and provides the multi-GPU scalability necessary for this study.…”

Section: Numerical Approach and General Plasma Conditionsmentioning

confidence: 99%

Kinetic modeling of three-dimensional electrostatic-solitary and surface waves in beam neutralization

Nuwal¹,

Levin²,

Kaganovich³

2022

Preprint

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This work studies the fundamental plasma processes involved in the neutralization of an ion beam's space-charge by electrons emitted by a filament using Particle-in-Cell simulations. While filament neutralization is economical, previous experiments have shown that a variety of waves become excited in this process that limit the space-charge neutralization. In this work, the formation and movement of electrostatic solitary waves (ESWs), which have low dissipation rates, are characterized for 2D planar and 3D cylindrical beams and are observed to generate waves that survive for a long time and slow the process of beam neutralization. Further, through a 1D Bernstein-Greene-Kruskal (BGK) analysis, we find that the non-Maxwellian nature of the beam electrons gives rise to large-sized ESWs that are not predicted by theory which assumes that the electrons may be described by a Maxwellian distribution. Our PIC simulations are sufficiently sensitive to be able to resolve important three-dimensional effects in a 3D cylindrical geometry that lead to the excitation of Trivelpiece-Gould surface waves due to high energy electrons present at the beginning of neutralization.

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Section: Numerical Approach and General Plasma Conditionsmentioning

confidence: 99%

Kinetic modeling of three-dimensional electrostatic-solitary and surface waves in beam neutralization

Nuwal¹,

Levin²,

Kaganovich³

2022

Preprint

Self Cite

View full text Add to dashboard Cite

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Multiscale modeling of fragmentation in an electrospray plume

Nuwal

Azevedo

Klosterman

et al. 2021

Journal of Applied Physics

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We present a 3D-particle-in-cell (PIC) approach to modeling electrospray plumes typical of those formed by externally wetted emitter devices. Numerical grid-resolution techniques suitable for capturing strong electric fields in the emitter region were explored, and grid refinement criteria were quantified. The molecular dynamics simulations of the EMIM−BF4 ionic liquid system were modeled to determine the fragmentation mechanism in the presence of an electric field and dimer temperature as well as to provide fragmentation rates for the PIC simulations. An energy analysis of the molecular dynamics (MD) fragmentation demonstrated that the key mechanism for dimer fragmentation corresponds to a decrease in the Coulomb energy between the cation and anion in the system and that dimers of temperatures 300 and 600 K are extremely stable for electric fields smaller than 1.5 V/nm. Using probabilities of fragmentation consistent with the MD simulations, we implemented a dimer fragmentation model in our PIC simulations. The ion energy distribution functions obtained from the PIC simulations were used to predict retarding potential analysis (RPA) curves that were compared directly to measurements. The sensitivity of the RPA shape to the fragmentation probability was found to be significant. By comparing predicted and measured RPA curves for both negative and positive operation modes, and the fact that dimers do not fragment for electric fields less than 0.6 V/nm, we conclude that fragmentation of dimers occurs spontaneously due to their high thermal energies.

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Kinetic modeling and experiments of a pulsed-bias plasma in a multipole plasma chamber

et al. 2022

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A pulse of electron timescale applied to a planar electrode immersed in a homogeneous plasma in a multipole plasma chamber (MPC) is modeled using a fully kinetic particle-in-cell (PIC) approach. In the time-explicit PIC simulations, we observed that the ion-sheath expansion is accompanied by electron timescale harmonic plasma oscillations at the sheath edge that decay after applying the pulse. First, we validate our PIC approach by comparing it with previous analytical and semi-empirical sheath expansion studies. Then, we compare our PIC results with experiments conducted in the MPC where similar electron frequency oscillations were excited when an electron timescale pulse was applied to a flat-conductor plate. In both PIC simulations and experiments, we find that the shape of the applied pulse dictates the amplitude of the sheath edge oscillations. In the PIC simulations, we observe that Landau damping has no discernible effect on these oscillations. However, in the experiments, the presence of a hot electron population results in a higher damping of electron oscillations. In both PIC simulations and experiments, the amplitude of the electron frequency oscillations decreases with the applied pulse width and these oscillations disappear for a linear pulse of a longer timescale of [Formula: see text] ([Formula: see text]), in the PIC simulations.

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Influence of secondary electron emission on plasma-surface interactions in the low earth orbit environment

Cited by 9 publications

References 45 publications

Kinetic modeling of three-dimensional electrostatic-solitary and surface waves in beam neutralization

Kinetic modeling of three-dimensional electrostatic-solitary and surface waves in beam neutralization

Multiscale modeling of fragmentation in an electrospray plume

Kinetic modeling and experiments of a pulsed-bias plasma in a multipole plasma chamber

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