Fluid modelling of the positive column of direct-current glow discharges

Alves, L. L.

doi:10.1088/0963-0252/16/3/015

Cited by 46 publications

(53 citation statements)

References 73 publications

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“…2 that comprises a total of 26 reactions involving electrons, molecular and atomic ions, lumped levels representing the set of four 4s levels (from 11.5 to 11.8 eV) and ten 4p levels (from 12.9 to 13.48 eV), and the argon dimer Ar 2 * . We adopt the local mean energy approximation; 20,21 that is, we assume the electron transport and rate coefficients are well-parameterized by the average electron energy. In Ref.…”

Section: à3mentioning

confidence: 99%

Modeling of microplasmas from GHz to THz

Gregório

Hoskinson

Hopwood

2015

Journal of Applied Physics

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We present a study of atmospheric-pressure microdischarges sustained over a wide range of continuous excitation frequencies. A fluid model is used to describe the spatial and temporal evolution of the plasma properties within a 200 μm discharge gap. At 0.5 GHz, the behavior is similar to a typical rf collisional discharge. As frequency increases at constant power density, we observe a decrease in the discharge voltage from greater than 100 V to less than 10 V. A minimum of the voltage amplitude is attained when electron temporal inertia delays the discharge current to be in phase with the applied voltage. Above this frequency, the plasma develops resonant regions where the excitation frequency equals the local plasma frequency. In these volumes, the instantaneous quasi-neutrality is perturbed and intense internal currents emerge ensuring a low voltage operation range. This enhanced plasma heating mechanism vanishes when the excitation frequency is larger than the local plasma frequency everywhere in the plasma volume. For a typical peak electron density of 5×1020 m−3, this condition corresponds to ∼0.2 THz. Beyond the plasma frequency, the discharge performs like a low loss dielectric and an increasingly large voltage is necessary to preserve a constant absorbed power.

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Section: à3mentioning

confidence: 99%

Modeling of microplasmas from GHz to THz

Gregório

Hoskinson

Hopwood

2015

Journal of Applied Physics

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“…In addition a novel drift-diffusion approximation for electrons is proposed. Results are compared to those of a conventional drift-diffusion model frequently used [24,25] and to kinetically obtained results at the example of argon gas discharge plasmas.…”

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confidence: 99%

Derivation of Moment Equations for the Theoretical Description of Electrons in Nonthermal Plasmas

Becker¹,

Loffhagen²

2013

APM

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The derivation of moment equations for the theoretical description of electrons is of interest for modelling of gas discharge plasmas and semiconductor devices. Usually, certain artificial closure assumptions are applied in order to derive a closed system of moment equations from the electron Boltzmann equation. Here, a novel four-moment model for the description of electrons in nonthermal plasmas is derived by an expansion of the electron velocity distribution function in Legendre polynomials. The proposed system of partial differential equations is consistently closed by definition of transport coefficients that are determined by solving the electron Boltzmann equation and are then used in the fluid calculations as function of the mean electron energy. It is shown that the four-moment model can be simplified to a new drift-diffusion approximation for electrons without loss of accuracy, if the characteristic frequency of the electric field alteration in the discharge is small in comparison with the momentum dissipation frequency of the electrons. Results obtained by the proposed fluid models are compared to those of a conventional drift-diffusion approximation as well as to kinetic results using the example of low pressure argon plasmas. It is shown that the results provided by the new approaches are in good agreement with kinetic results and strongly improve the accuracy of fluid descriptions of gas discharges.

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“…21of Ref. 23 is incorrect. Other formulations may require extensive numerical calculations to elucidate the pivotal role of mean energy.…”

Section: B Average Collision Ratesmentioning

confidence: 98%

Fundamental issues in fluid modeling: Direct substitution and aliasing methods

Robson

Nicoletopoulos

Hildebrandt

et al. 2012

The Journal of Chemical Physics

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It is shown how the accuracy of fluid models of charged particles in gases can be improved significantly by direct substitution of swarm transport coefficient data, rather than cross sections, into the average collision terms. This direct substitution method emerges in a natural way for fluid formulations in which the role of the mean energy is transparent, whatever the mass of the charged particles in equation (ions or electrons), and requires no further approximations. The procedure is illustrated by numerical examples for electrons, including the operational window of E/N for an idealized Franck-Hertz experiment. Using the same fluid formulation, we develop an aliasing method to estimate otherwise unknown mobility data for one type of particle, from known mobility data for another type of particle. The method is illustrated for muons in hydrogen, using tabulated data for protons in the same gas.

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Fluid modelling of the positive column of direct-current glow discharges

Cited by 46 publications

References 73 publications

Modeling of microplasmas from GHz to THz

Modeling of microplasmas from GHz to THz

Derivation of Moment Equations for the Theoretical Description of Electrons in Nonthermal Plasmas

Fundamental issues in fluid modeling: Direct substitution and aliasing methods

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