Magnetic cusp confinement in low-β plasmas revisited

Jiang, Y.; Fubiani, G.; Garrigues, Laurent; Boeuf, Jean-Pierre

doi:10.1063/5.0014058

Cited by 7 publications

(5 citation statements)

References 27 publications

(52 reference statements)

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“…The 2D version J-PIC has been used in several recent papers on the simulation of magnetized plasmas (see, e.g., Refs. [26][27][28][29][30][31][32] ). J-PIC is based on standard features of the electrostatic PIC-MCC method as described by Birdsall 25 .…”

Section: Pic-mcc Modelmentioning

confidence: 99%

Ionization waves (striations) in a low-current plasma column revisited with kinetic and fluid models

Boeuf

2022

Physics of Plasmas

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A one-dimensional Particle-In-Cell Monte Carlo Collisions (PIC-MCC) method has been used to model the development and propagation of ionization waves in neon and argon positive columns. Low current conditions are considered, i.e. conditions where stepwise ionization or Coulomb collisions are negligible (linear ionization rate). This self-consistent model describes the development of self-excited moving striations, reproduces many of the well-known experimental characteristics (wavelength, spatial resonances, potential drop over one striation, electron "bunching" effect) of the ionization waves called p, r and s waves in the literature and sheds light on their physical properties and on the mechanisms responsible for their existence. These are the first fully kinetic self-consistent simulations over a large range of conditions reproducing the development of p, r and s ionization waves. Although the spatial resonances and the detailed properties of the striations in the non-linear regime are of kinetic nature, the conditions of existence of the instability can be obtained and understood from a linear stability analysis of a three-moment set of quasi-neutral fluid equations where the electron transport coefficients are expressed as a function of electron temperature and are obtained from solutions of a 0D Boltzman equation. An essential aspect of the instability leading to the development of these striations is the non-Mawellian nature of the electron energy distribution function in the uniform electric field prior to the instability onset, resulting in an electron diffusion coefficient in space much larger than the energy diffusion coefficient.

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Section: Pic-mcc Modelmentioning

confidence: 99%

Ionization waves (striations) in a low-current plasma column revisited with kinetic and fluid models

Boeuf

2022

Physics of Plasmas

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“…In order to increase the degree of ionisation, Surrey and Holmes [1] suggested to confine the plasma electrons by a magnetic cusp field along all boundaries. In their model, they describe this confinement by an effective loss area that is equal to the total length of the cusp lines times the hybrid Larmor radius [18]. The accuracy of the predicted plasma density and degree of ionisation in the neutraliser, and consequently the achievable neutralisation yield, depend critically on the correctness of this description of the wall losses.…”

Section: Design Of a Beam-driven Plasma Neutralisermentioning

confidence: 99%

“…As we are not aware of any expression that is able to describe the plasma magnetic confinement for any value of the plasma parameters, e.g. gas pressure and ion and electron temperatures, and for any magnetic field and cusp arrangement [18], we continue to use equation ( 18) although it might oversimplify the plasma wall loss modelling. Hence, A loss is another important source of uncertainty which requires to be addressed in future.…”

Section: Electron-ion Recombination and The Plasma Species Compositio...mentioning

confidence: 99%

On suitable experiments for demonstrating the feasibility of the beam-driven plasma neutraliser for neutral beam injectors for fusion reactors

2022

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Plasma neutralisers promise increased neutralisation eﬃciency of negative ion beams in neutral beam injection (NBI) beamlines compared with gas neutralisers. It has been suggested that, in the presence of an electron-conﬁning magnetic cusp ﬁeld along all neutraliser walls, the beam itself could ionise the neutraliser gas suﬃciently to take advantage of this eﬀect, avoiding the added complexity of external power coupling to the neutraliser. These predictions come from a zero-dimensional model by Surrey and Holmes [1] and Turner and Holmes [2]. We have revisited and modiﬁed this model by introducing slowing-down energy distributions for stripped and Rudd electrons, including electron impact dissociation as an electron energy loss channel and taking into account dissociative recombination of molecular ions with electrons. Including the latter eﬀect reduces the predicted plasma density by about a factor of four and the achievable neutralisation yield from ∼ 80 % to 68 % in the case of a negative deuterium ion beam with an energy of 1 MeV and a current of 40 A. With this revised model we estimate the expected performance of potential beam-driven plasma neutralisers (BDPN) on a variety of existing negative ion beam test facilities for neutral beam injection. Based on these results, we conclude that the most suitable proof-of-principle experiment would be a dedicated chamber, ideally of the same dimensions and with the same magnetic cusp conﬁguration as a BDPN for the DEMO NBI, in which the plasma is not created primarily by the fast electrons stripped from the beam ions, but by electrons of similar current and energy emitted from biased ﬁlaments.

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“…This magnetic field configuration is widely used in plasma sources because of its role in confining the plasma and reducing particle loss. The applications of multi-cusp magnetic fields encompass a broad spectrum of topics [1][2][3][4][5][6][7][8][9][10][11][12]. The most common application resides in the field of ion source development, where these fields have yielded enhancements in the confinement of hot and bulk electrons [13,14].…”

Section: Introductionmentioning

confidence: 99%

Spatial Distribution Analyses of Axially Long Plasmas under a Multi-Cusp Magnetic Field Using a Kinetic Particle Simulation Code KEIO-MARC

Nishimura,

Seino,

Yoshimura

et al. 2024

Plasma

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To realize the development of a long plasma source with a uniform electron density distribution in the axial direction, the spatial distribution of plasma under a multi-cusp magnetic field was analyzed using a KEIO-MARC code. Considering a cylindrical plasma source with an axial length of 3000 mm and a cross-sectional diameter of 100 mm, in which the filament electrode was the electron source, the electron density distribution was calculated using the residual magnetic flux density, Bres, and the number of permanent magnets installed at different locations surrounding the device, Nmag, as design parameters. The results show that both Bres and Nmag improved the uniformity of the electron density distribution in the axial direction. The maximum axial electron density decreased with increasing Nmag and increased with increasing Bres. These trends can be explained by considering the nature of the multi-cusp field, where particles are mainly confined to the field-free region (FFR) near the center of the plasma column, and the loss of particles due to radial particle transport. The use of multiple filaments at intervals shorter than the plasma decay length dramatically improved axial uniformity. To further improve axial uniformity, the filament length and FFR must be properly set so that electrons are emitted inside the FFR.

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Magnetic cusp confinement in low-β plasmas revisited

Cited by 7 publications

References 27 publications

Ionization waves (striations) in a low-current plasma column revisited with kinetic and fluid models

Ionization waves (striations) in a low-current plasma column revisited with kinetic and fluid models

On suitable experiments for demonstrating the feasibility of the beam-driven plasma neutraliser for neutral beam injectors for fusion reactors

Spatial Distribution Analyses of Axially Long Plasmas under a Multi-Cusp Magnetic Field Using a Kinetic Particle Simulation Code KEIO-MARC

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