The type and extent of non-LTE in argon arcs at 0.1-10 bar

Eddy, T.L.; Sedghinasab, A.

doi:10.1109/27.3858

Cited by 17 publications

(5 citation statements)

References 20 publications

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“…The major source of error in the absolute-intensity method is the uncertainty in the transition probability used. It has been found by Eddy and Sedghinasab [23] that the same corrections to transition probabilities do not make a significant change in the temperature but would make larger changes in the species' densities because of the exponential effects. An overall extent of departures from LTE is indicated by these figures.…”

Section: Resultsmentioning

confidence: 84%

The effect of pressure on a plasma plume: temperature and electron density measurements

Singh

Razafinimanana

Gleizes

1998

J. Phys. D: Appl. Phys.

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Measurements of temperature and electron number density measurements have been carried out on a plasma plume under various pressure conditions (p = 1-0.3 bar) using emission spectroscopy. The anode nozzle used does not generate a shock wave or an expansion-compression zone. Ar- (1%) is used as the plasma gas. Temperature values are obtained from various lines of neutral argon. Electron number densities are obtained from the Stark-effect broadening of the 486.1 nm H line and the continuum measurements. Measurements of temperature and density profiles reveal the general features of a low-pressure plasma jet, namely relatively low temperature and long heating zone of the expanded jet. The LTE criterion is satisfied at higher pressures ( bar). Deviations from ionization equilibrium occur at lower pressure. The variation of excited neutral argon and states has been studied for lower pressures. tends to be overpopulated compared with .

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Section: Resultsmentioning

confidence: 84%

The effect of pressure on a plasma plume: temperature and electron density measurements

Singh

Razafinimanana

Gleizes

1998

J. Phys. D: Appl. Phys.

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“…On the other hand, some workers have provided spectroscopic evidence for departures from LTE near the cathode of similar arcs [4][5][6]. Moreover, it has been suggested that the departure from LTE in argon arcs is extensive up to a pressure of 3 [7] or even 5 atm [8]. In hydrogen the critical number density for complete LTE at 20 000 K has been given as 2 × 10 24 m −3 [9].…”

Section: Introductionmentioning

confidence: 99%

A departure from local thermodynamic equilibrium within a freely burning arc and asymmetrical Thomson electron features

Bentley¹

1997

J. Phys. D: Appl. Phys.

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Spectrally resolved measurements of Thomson scattering were made in a freely burning arc in argon at a pressure of 1 atm. The radial and axial profiles in electron temperature and number density exhibited extensive regions of departure from local thermodynamic equilibrium, so confirming the findings of Snyder et al in E 48 4124 - 7, 1993. Electron temperatures at least 4000 K above those of the gas were found. Asymmetry in the Thomson electron feature was found and shown to depend on which segment of the laser-profile scattering data was sourced. This arises from an asymmetry in the arc - laser interaction. Also described is a simple technique for accurately defining the position of the cathode tip once an arc has been ignited.

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“…Modelling high pressure arcs, and in particular their temperature distribution, is useful for the development of high power light sources, arc-jet thrusters, and arc welding processes [1][2][3]. In two extreme cases, theoretical modelling is relatively simple: (1) If the arc plasma is transparent to its own thermal radiation, energy loss may be described in terms of a 'sink', by including a radiation term in the energy balance equation [4][5][6]. (2) If the plasma column is completely opaque to its own thermal radiation, the radiation is in local thermodynamic equilibrium and radiative heat conductivity can be determined from well-known expressions for the radiation intensity and density [4,7].…”

Section: Introductionmentioning

confidence: 99%

Theoretical modelling of high pressure argon arc radiation

Gidalevich

Goldsmith

Boxman

2002

Plasma Sources Sci. Technol.

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A one-dimensional, axisymmetric, high-pressure argon arc was modelled theoretically, and its radiation spectrum was calculated numerically from the equations of heat conductivity and radiation transfer. For a pressure of P = 15 atm, the coefficients of absorption in argon were calculated for the continuum and line spectra. The coefficient of radiative heat conductivity was found, subject to the assumptions that the continuum optical depth is less than unity while the line optical depth is much more than unity. The general heat conductivity was found by neglecting convection, but taking into account radiative conductance and kinetic conductance by ions, electrons and neutral atoms. The radial distributions of the temperature, ionization degree and electrical conductivity were found for arcs with currents I = 880, 990 and 1250 A confined in a transparent tube of radius R = 0.01 m. The degree of ionization was calculated assuming local thermodynamic equilibrium. An effective temperature was calculated in the spectral region of 300-3000 nm. For I = 880 and 1250 A, the effective temperatures were found to be 7500 and 8700 K and the maximum spectral radiant intensities were 7.5 × 10 −8 and 10.5 × 10 −8 W m −2 Hz −1 , respectively.

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The type and extent of non-LTE in argon arcs at 0.1-10 bar

Cited by 17 publications

References 20 publications

The effect of pressure on a plasma plume: temperature and electron density measurements

The effect of pressure on a plasma plume: temperature and electron density measurements

A departure from local thermodynamic equilibrium within a freely burning arc and asymmetrical Thomson electron features

Theoretical modelling of high pressure argon arc radiation

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