Numerical study of the plasma wall-bias effect on the ion flux through acceleration grid hole

Park, Seung-Hoon; Chang, C. S.

doi:10.1063/1.3455538

Cited by 3 publications

(8 citation statements)

References 18 publications

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“…Obviously, n p and A represent the plasma parameters, B and C are the local characteristics of the extraction field. So, equation (10) describes the conditions under which the ion optics will match with the plasma. There will be a ζ ∈ [−t s , 0] to make equation (10) hold when the plasma matches with the ion optics.…”

Section: One-dimensional Matching Model Of Ion Opticsmentioning

confidence: 99%

“…So, equation (10) describes the conditions under which the ion optics will match with the plasma. There will be a ζ ∈ [−t s , 0] to make equation (10) hold when the plasma matches with the ion optics. However, for the sake of simplicity, we analyze the matching relation between the ion optics and plasma with γ o rather than ζ.…”

Section: One-dimensional Matching Model Of Ion Opticsmentioning

confidence: 99%

“…There is a critical density where the density higher than that will not satisfy equation (10). Note that D = (B + C)/2 because max( ∂ϕ L ∂z ) = ∂ϕ L ∂z z=−t s , then the critical density n p,max can be calculated by…”

Section: One-dimensional Matching Model Of Ion Opticsmentioning

confidence: 99%

“…Some earlier works tried to simulate the formation of the upstream sheath or even presheath self-consistently [20,21], but it was proved by Li and Sun [22] that the local model of ion optics can only describe a given sheath and is unable to form the presheath. Therefore, the simulations of positive ion extraction were more effective in the investigations of the beam characteristics and grid erosion [11,[23][24][25] or the ion dynamics in the sheath field [4,10]. Consequently, the structure particularity of the ion optics makes it difficult for experiments and simulations to analyze the detailed sheath characteristics and the mechanism of its effect on beam divergence.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, theoretical modeling and analyses are integral to the study of ion optics. The characteristics of the sheath upstream of ion optics, such as the sheath thickness and space charge-limited ion current, were commonly evaluated with the models and conclusions of the sheath near a plate electrode [3,4,10,24]. However, experiments demonstrated that the potential distribution of the sheath near ion optics differs from that near a plate electrode [16,17], and Li et al [16] thought the difference resulted from the transmission of the ions through the grid apertures.…”

Section: Introductionmentioning

confidence: 99%

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Numerical and theoretical modeling of the sheath upstream of ion optics: sheath structure transition and its effect on the beam divergence

Li¹,

Yuan²,

Yang³

et al. 2021

Plasma Sources Sci. Technol.

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The grasp of the sheath characteristics is fundamental to evaluate the extraction capabilities of ion optics and accommodate the wide application of ion sources. A one-dimensional theoretical model is developed to investigate the sheath upstream of ion optics as well as the matching relation between the ion optics and plasma, by simplifying and decomposing the Poisson's equation at the outer surface and centerline of the grid aperture. The one-dimensional model is validated by 2D3V hybrid simulations which are also applied to visualize the sheath structure and ion beam divergence. With the increase of plasma density, it is found that the upstream sheath will transform gradually into a sheath near the plate electrode at first and then enter the screen aperture with a sheath edge approximately paralleling to the meniscus. Accordingly, the structure of the upstream sheath can be classified into four kinds which correspond to different beam divergence. The structure transition of the upstream sheath reflects the interaction between the extraction field and plasma, and the ion optics is considered to work at the matching point when the plasma is relatively balanced with the extraction field. Around the matching point, a small beam divergence angle can be achieved without the occurrence of over-perveance. Then a matching model is proposed based on the characteristics of the potential distribution at the matching point. It is verified to be effective of the model for quickly analyzing the ion beam divergence characteristics and determining an ideal operating range of the ion optics.

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Section: One-dimensional Matching Model Of Ion Opticsmentioning

confidence: 99%

Section: One-dimensional Matching Model Of Ion Opticsmentioning

confidence: 99%

Section: One-dimensional Matching Model Of Ion Opticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Numerical and theoretical modeling of the sheath upstream of ion optics: sheath structure transition and its effect on the beam divergence

Li¹,

Yuan²,

Yang³

et al. 2021

Plasma Sources Sci. Technol.

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Side extraction: A novel method of filtering ions or macro-particles for vacuum arc ion sources

Wang

Huang

Zeng

et al. 2018

Review of Scientific Instruments

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A novel ion-extraction method named side extraction, i.e., extracting ions from the direction perpendicular to that of plasma expansion, is proposed in this paper, which can be used to filter ions or macro-particles for vacuum arc ion sources. Particle-in-cell simulations were performed to study filtering effects of side extraction on ions with different mass, different charges, and different initial kinetic energies. The results indicate that side extraction can separate ions by their charge states or initial kinetic energies and the extracting efficiency for different ion species is identical. Influences of extraction voltages, extraction interval, and the aspect ratio of the extraction aperture on ion filtering effects were also studied, which suggests that lower extraction voltages and longer extraction interval are beneficial for ion filtering and a high-aspect-ratio aperture contributes to the increase in the ratio of lighter ions in extracted beams. A theoretical analysis on the deflected distance of beams in the y direction was made and shows good agreement with the simulation results.

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Structural characteristics of the upstream sheath of the ion optics and its application in evaluating the beam performance of an ion thruster

Yang

Zhang

et al. 2022

Journal of Applied Physics

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To evaluate the extraction capabilities of ion optics and promote the generation of highly collimated ion beams for propulsion, the properties of the upstream sheath of the ion optics and how those properties relate to the beam divergence are investigated numerically and theoretically. The characteristics of the beam divergence at different grid parameters are studied from the behaviors of the impingement current and divergence angle obtained by simulations. Additionally, the simulations indicate the existence of an optimal structure for the upstream sheath of the ion optics, one that corresponds to a moderate focusing effect and a relatively small divergence angle. The plasma densities at the dividing points of different sheath structures are then derived with the matching model of the ion optics and the Child–Langmuir law, coupled with semi-empirical approaches based on the simulation results. According to the theoretical analyses, the range of existence of the most-desirable sheath structure depends on the strength of the penetration of the extraction field, the voltage between the grid apertures, and the distance between the upstream surfaces of the grids. Also, sensitivity analyses are performed with the numerical partial derivatives of the models to investigate how the grid parameters affect the sheath structures. The plasma densities at the dividing points generally vary synchronously with the changes of grid parameters, but the ranges of variations are different. Consequently, the desirable sheath structure and operating conditions of the ion optics can be achieved by correctly adjusting the grid parameters.

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Numerical study of the plasma wall-bias effect on the ion flux through acceleration grid hole

Cited by 3 publications

References 18 publications

Numerical and theoretical modeling of the sheath upstream of ion optics: sheath structure transition and its effect on the beam divergence

Numerical and theoretical modeling of the sheath upstream of ion optics: sheath structure transition and its effect on the beam divergence

Side extraction: A novel method of filtering ions or macro-particles for vacuum arc ion sources

Structural characteristics of the upstream sheath of the ion optics and its application in evaluating the beam performance of an ion thruster

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