Self-Consistent Description of Radial Space-Charge Confinement in DC Column Plasmas

Schmidt, Martin; Uhrlandt, Dirk; Winkler, R.

doi:10.1006/jcph.2000.6676

Cited by 5 publications

(7 citation statements)

References 33 publications

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“…The symbol û ≡ û(r, ε) = ε − w(r) is used to express the kinetic energy as a function of the variables r and ε. Equation ( 2) is completed by appropriate boundary conditions which are presented and explained already in previous papers [2,9,11,12].…”

Section: Description Of the Electrons And Excited Atomsmentioning

confidence: 99%

“…Monte Carlo simulations of the charge carriers in column plasmas as applied in [1] seem to be appropriate for gas pressures below about 5 Pa only. Expensive non-linear optimization methods have been used in [2,9] to couple the space-dependent electron kinetic equation with the fluid equations of ions and the Poisson equation. The so-called nonlocal moment method [10] has a large efficiency.…”

Section: Introductionmentioning

confidence: 99%

“…The hybrid method is based on the same physical assumptions made in [2] and yields results of the same accuracy. But the new method reduces the computation time by a factor of about 50 in comparison with the method applied in [2,9] and, hence, may also be used as a framework for the development of models of more complex discharge situations.…”

Section: Introductionmentioning

confidence: 99%

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Study of a neon dc column plasma by a hybrid method

Uhrlandt

Franke

2002

J. Phys. D: Appl. Phys.

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The column plasma of a dc glow discharge in neon is comprehensively studied by a new self-consistent hybrid method. The method is based on the solution of the steady-state fluid equations of charge carriers and the Poisson equation using electron transport coefficients and ionization frequencies which arise from a space-dependent kinetic treatment of the electron component. The column description comprises, in addition, a space-dependent treatment of the excited particles in the plasma, the treatment of the plasma-wall interaction processes of the charge carriers and the determination of the electric field. The hybrid method provides a very efficient self-consistent column description although it avoids rough approximations often applied in fluid methods. Results of the method for a neon column plasma are compared with those of probe measurements and spectroscopic studies. The results confirm the importance of the ionization of excited neon atoms for the charge carrier production and emphasize the necessity of the detailed description of the excited states included in the column model.

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Section: Description Of the Electrons And Excited Atomsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Study of a neon dc column plasma by a hybrid method

Uhrlandt

Franke

2002

J. Phys. D: Appl. Phys.

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“…With the appropriate transformations and spatial averaging, the Boltzmann equation in the nonlocal approach can be treated as an ordinary differential equation in the independent variable ⑀. 18 -20 How-ever, in the pressure range of a few Torr, Schmidt et al 21 have shown that the inclusion of the spatial gradient term in the Boltzmann equation for the electron kinetics is required to accurately model radial space-charge confinement. Ambipolar diffusion produces a radial polarization field which, near the enclosing wall, can be significantly greater than the applied, axial field.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the appropriate treatment for the standard fluorescent lamp would be a fully 1D Boltzmann solution for the EEDF wherein the complete dependence of the EEDF is accounted for, f ϭ f (r,u). Fundamental work has been described in the literature on the 1D Boltzmann model, [21][22][23][24][25][26][27][28][29] but none has addressed its application to the mixed composition found in a fluorescent lamp.…”

Section: Introductionmentioning

confidence: 99%

Inhomogeneous model of an Ar–Hg direct current column discharge

Petrov¹,

Giuliani

2003

Journal of Applied Physics

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The inhomogeneous electron Boltzmann equation is solved for an Ar-Hg positive column direct current glow discharge with properties similar to the standard fluorescent lamp. The inhomogeneity arises from the ambipolar potential and requires the inclusion of the spatial gradient term in the Boltzmann equation. The electron kinetics is coupled to a collisional-radiative equilibrium model for various states of Ar and Hg subject to a reaction set with electron and heavy particle collisions. The axial electric field and space-charge potential are solved self-consistently. The calculated electron distribution function satisfies neither the local nor nonlocal approaches, but rather is found to be a function of both the electron energy and radial position. The radial dependence produces an energy flow from one part of the discharge to another, which results in nonuniform ultraviolet radiative power. Results are given for global properties of the discharge such as power per unit length and axial electric field, as well as spatially averaged quantities ͑densities, electron and gas temperatures, and emission powers͒ as a function of the wall temperature and the current. Extensive comparisons are presented with experimental data and previous homogeneous Boltzmann models of the discharge. The optimum current and fill pressures are determined and the general trends of varying the input parameters are established. There is general agreement between the present model and data, except that the calculated average electron density is larger than the measured values.

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

Alves¹

2007

Plasma Sources Sci. Technol.

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This paper presents a tutorial on the fluid modelling of the positive column of direct-current cylindrical glow discharges. The model writes the continuity and momentum-transfer equations for electrons and ions, coupled with Poisson's equation and the electron mean energy transport equations. The model is solved for helium at pressures p 0.1-10 Torr, gas temperature T g = 500 K, discharge currents I dc = 5-200 mA, and tube radius R = 1 cm. The electron transport parameters and rate coefficients are calculated using the local mean energy approximation in articulation with a two-term Boltzmann solver. Model equations are integrated from the discharge axis to the wall, passing through the space-charge sheath and monitoring the charge separation within it. The results obtained allow a systematic characterization of discharge energy deposition and space-charge sheath formation, as a function of pressure and axial current. A general good agreement is found between model results and experimental measurements available in the literature.

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Self-Consistent Description of Radial Space-Charge Confinement in DC Column Plasmas

Cited by 5 publications

References 33 publications

Study of a neon dc column plasma by a hybrid method

Study of a neon dc column plasma by a hybrid method

Inhomogeneous model of an Ar–Hg direct current column discharge

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

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