Response of beam focusing to plasma fluctuation in a filament-arc-type negative ion source

Haba, Y.; Nagaoka, K.; Tsumori, K.; Kisaki, M.; Takahashi, Kazunori; Nakano, H.; Ikeda, K.; Yoshimura, S.; Osakabe, M.

doi:10.35848/1347-4065/ab7473

Cited by 7 publications

(7 citation statements)

References 32 publications

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“…These two special boundaries are closely related to the meniscus which is an equipotential surface extending from the screen grid to the plasma and intersecting with the centerline (cf figure 1). The shape of the meniscus characterizes the interaction between the ion optics and plasma, so it is a key parameter reflecting the beam divergence [44][45][46][47]. Thus, the upstream sheath and its connection with the beam divergence will be investigated more thoroughly by taking the meniscus as a bridge if the potential distributions at the outer surface and centerline can be modeled in one dimension.…”

Section: Simulation Methods and Model Configurationmentioning

confidence: 99%

“…It can be known from figure 2 that the radial electric field will be gradually offset and even reversed with the increase of n p . The value of Δn i,L and its effects on the potential distribution further demonstrate that the interaction between the extraction field and plasma determines the structure of the upstream sheath and the ion beam divergence [45][46][47]. Accordingly, as illustrated in figure 6, the structure of the upstream sheath can be classified into four kinds which correspond to different ion beam divergence.…”

Section: Numerical Analyses Of the Upstream Sheathmentioning

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: Simulation Methods and Model Configurationmentioning

confidence: 99%

Section: Numerical Analyses Of the Upstream Sheathmentioning

confidence: 99%

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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“…This observation indicates that only the curvature of the equipotential lines near the hole edge of the extraction grid temporally oscillates for the positive ion beam source. The oscillation of the beam divergence in the negative ion beam source has also been observed and investigated in detail in a Researchand-Development Negative Ion Source in NIFS [81], indicating the importance of source plasma stability. More recently, oscillation in the rf negative ion source has been observed; control of the rf potential oscillation may be required for the performance improvement of the rf negative ion source [82,83].…”

Section: Fusion-relevant Plasmasmentioning

confidence: 96%

Magnetic Nozzle Radiofrequency Plasma Systems for Space Propulsion, Industry, and Fusion Plasmas

TAKAHASHI

Charles

Boswell

et al. 2023

Plasma and Fusion Research

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Low-pressure radiofrequency (rf) plasma sources have been widely used in various fields. When static magnetic fields are applied to these sources, a diverging magnetic field configuration known as a magnetic nozzle forms downstream of the source and interesting phenomena are observed. Such structures are frequently observed in space, e.g., the surface of the Sun and the geomagnetic fields. Here, the studies performed by the authors over the last decade on the fundamental plasma physics, the space plasma propulsion, the industrial plasma technology, and the radiofrequency ion source, are briefly overviewed. The design of sources based on the type of application is an important issue. Integrating a rf plasma source into a system often requires a compact and automatically controlled system, as presented here. Herein, interaction between the low-temperature plasmas and the hot fusion plasmas is sometimes mentioned in terms of "Plasma Apparatus."

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“…Recently, an oscillation of negative ion beamlet with the same frequency as the RF frequency was observed by the emittance measurement with high-time resolution in the RF negative ion source for J-PARC [3]. In the filamentarc type negative ion source, the beamlet was also observed to responses to the plasma density oscillation in the vicinity of the plasma grid [4]. These experimental observations suggest the importance of the meniscus stability for the negative ion beam focusing.…”

Section: Introductionmentioning

confidence: 91%

Beam instability in the vicinity of beam extraction region of negative ion source

Nagaoka

Nakamoto

Sasaki

et al. 2022

J. Phys.: Conf. Ser.

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Beam instability in the presheath region of negative ion beam extraction is investigated in theoretically and experimentally. The linear stability analysis shows that the beam instability is unstable due to coupling between positive ion flow and negative ion flow. On the other hand, no clear activity can be seen in the experiment in the frequency range predicted by the theory. The beam instability in the presheath region of negative ion beam extraction may not cause the degradation of the beam focusing because of collisional damping and/or Landau damping.

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Response of beam focusing to plasma fluctuation in a filament-arc-type negative ion source

Cited by 7 publications

References 32 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

Magnetic Nozzle Radiofrequency Plasma Systems for Space Propulsion, Industry, and Fusion Plasmas

Beam instability in the vicinity of beam extraction region of negative ion source

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