The diffusion length for gas discharge columns with electron production and loss rates linear and quadratic in electron density

Rogoff, Gerald L.

doi:10.1063/1.328612

Cited by 10 publications

(2 citation statements)

References 8 publications

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“…In section 3 the methodology and physical basis of the 'LTE-diffusion approximation' is presented, under which we assume LTE, but use a mesh size at the electrodes set at the diffusion length, , defined by D e /W , where D e is the electron diffusion coefficient and W is the electron drift velocity. This diffusion length, which is a property of the arc plasma, will be shown to be ∼0.1 mm for arcs with currents of the order of 200 A at 1 bar, and is distinct from some other definitions of diffusion length, for example, defined by 1/ 2 = −∇ 2 n e /n e , in which case is just proportional to the radius of the discharge, at least for ionization linear in n e (Rogoff 1981). Section 4 discusses the effect of neglect in our approximation of the large diffusion currents that occur at the electrodes.…”

Section: Introductionmentioning

confidence: 76%

‘LTE-diffusion approximation’ for arc calculations

Lowke

Tanaka

2006

J. Phys. D: Appl. Phys.

161

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This paper proposes the use of the ‘LTE-diffusion approximation’ for predicting the properties of electric arcs. Under this approximation, local thermodynamic equilibrium (LTE) is assumed, with a particular mesh size near the electrodes chosen to be equal to the ‘diffusion length’, based on De/W, where De is the electron diffusion coefficient and W is the electron drift velocity. This approximation overcomes the problem that the equilibrium electrical conductivity in the arc near the electrodes is almost zero, which makes accurate calculations using LTE impossible in the limit of small mesh size, as then voltages would tend towards infinity. Use of the LTE-diffusion approximation for a 200 A arc with a thermionic cathode gives predictions of total arc voltage, electrode temperatures, arc temperatures and radial profiles of heat flux density and current density at the anode that are in approximate agreement with more accurate calculations which include an account of the diffusion of electric charges to the electrodes, and also with experimental results. Calculations, which include diffusion of charges, agree with experimental results of current and heat flux density as a function of radius if the Milne boundary condition is used at the anode surface rather than imposing zero charge density at the anode.

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Section: Introductionmentioning

confidence: 76%

‘LTE-diffusion approximation’ for arc calculations

Lowke

Tanaka

2006

J. Phys. D: Appl. Phys.

161

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“…As the diffusion coefficient obtained using Fuller's method tends to be 10%-30% greater than the measured value [39], it was divided by 1.2 in this study. The characteristic diffusion length is given by [40] 1…”

Section: Production and Loss Of Ohmentioning

confidence: 99%

Measurement of the density and rotational temperature of OH in a saturated water vapor slot-excited microwave plasma

Inoue¹,

Aizawa²,

Ishijima³

et al. 2021

J. Phys. D: Appl. Phys.

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OH density and rotational temperature were measured in a saturated water vapor slot-excited microwave plasma using spatio-temporally resolved laser-induced fluorescence. The microwave power was 20–100 W under continuous wave mode, whereas 40–200 W peak under pulse-modulated mode (30% duty cycle, 100 Hz). The water vapor pressure was 2.3 kPa. An approximately 2 mm thick flat-shaped plasma was generated on the surface of a slot antenna. The OH density and rotational temperature in the plasma ranged from 1 × 1014 cm−3 to 1 × 1015 cm−3 and from 1100 K to 3000 K, respectively. OH was produced via various routes originating from electron collisions (e + H2O) and was primarily lost through recombination (OH+OH → H2O+O) and diffusion. The production rate (k p ) of OH per H2O molecule, which was calculated based on a simplified reaction model using the measured OH density and temperature, showed a relation of k p / [ H 2 O ] ∝ P 1.8 , where P represents the microwave power. This relationship implies a two-step production process of OH via the vibrational excitation of H2O. Although the OH density increased with increasing microwave power, the density became saturated at high power values.

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Electrical breakdown characteristics of an atmospheric pressure rf capacitive plasma source

Kang

Uhm

2005

Physics of Plasmas

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Articles you may be interested inDevelopment of a diffuse air-argon plasma source using a dielectric-barrier discharge at atmospheric pressureThe electrical breakdown characteristics of the rf capacitive plasma source are investigated theoretically and experimentally. The plasma source is the electrode type consisting of the concentric cylinders for generating nonequilibrium plasma at atmospheric pressure. The theoretical model based on the diffusion-controlled breakdown mechanism is proposed to analyze the electrical breakdown phenomenon in this rf capacitive plasma source of the coaxial cylinders. The electron temperature at the electrical breakdown is calculated from the theoretical model, thereby evaluating the electrical breakdown voltages. The experimental data of the electrical breakdown voltage are measured with respect to the variation of the geometric parameters of plasma source, the gas temperature, and the concentration of the foreign reactive gases ͑oxygen and nitrogen͒ mixed in the helium gas. The theoretical results of the electrical breakdown voltage agree remarkably well with experimental data. This indicates that not only the electron temperature is important in determining the electrical breakdown voltage, but also the geometric variables, the gas temperature, and the scattering cross sections of molecules play significant roles.

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The diffusion length for gas discharge columns with electron production and loss rates linear and quadratic in electron density

Cited by 10 publications

References 8 publications

‘LTE-diffusion approximation’ for arc calculations

‘LTE-diffusion approximation’ for arc calculations

Measurement of the density and rotational temperature of OH in a saturated water vapor slot-excited microwave plasma

Electrical breakdown characteristics of an atmospheric pressure rf capacitive plasma source

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