A Role of Excited States in Collisional-Radiative Model for Non-Equilibrium Cesium Plasma

Abstract The thermal helium beam diagnostic at ASDEX Upgrade is used to infer the electron density ne and temperature Te in the scrape-off layer and the pedestal region from the emission of visible lines of the locally injected helium. The link between ne and Te and the emission is provided by a collisional radiative model, which delivers the evolution of the populations of the relevant excited states as the He atoms travel through the plasma. A computationally efficient method with just three effective states is shown to provide a good approximation of the population dynamics. It removes an artificial rise of Te at the plasma edge when using a simple static model. Furthermore, the re-absorption of the vacuum ultra-violet resonance lines has been introduced as additional excitation mechanism being mainly important in the region close to the injection point. This extra excitation leads to a much better fit of the measured line ratios in this region for larger puff rates.

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Investigation of Excited States of Helium Atoms in a Stationary PIG-Discharge

Zeitschrift für Naturforschung A ◽

10.1515/zna-1971-0202 ◽

1971 ◽

Vol 26 (2) ◽

pp. 186-197 ◽

Cited By ~ 2

Author(s):

H. W. Drawin ◽

F. Klan ◽

H. Ringler

Keyword(s):

Excited States ◽

Theoretical Calculations ◽

Principal Quantum Number ◽

Population Densities ◽

Boltzmann Plot ◽

Line Intensities ◽

Quantum Numbers ◽

Collisional Radiative Model ◽

Radiative Model ◽

Large Experimental Error

AbstractSpectral line intensities emitted by a quiescent PIG-discharge have been measured and the population densities up to a principal quantum number n = 24 have been derived from them. The experimentally determined population densities have been compared with theoretical ones calculated on the basis of a collisional-radiative model in which one accounts for electron and atom collisions. I t is shown that even in the case of different electron and atom temperatures, Te and Ta, an evaluation of the Boltzmann plot at medium and moderately high quantum numbers always leads to the electron temperature, whereas the Saha-Eggert equation for the same states may yield incorrect electron densities. The theoretical calculations predict an inflection of the slope of the Boltzmann plot from Te to Ta for very highly excited states. For the plasma para meters under which the PIG-discharge was operated (ne ≅ 2.5 × 1012 cm-3, Te ≅ 1200°K, n0 ≅ 1.5 × 1015 cm-3, 300°K) the change of the slope should become visible for states having principal quantum numbers n > 18. Due to the large experimental error bars it was not possible to check this behaviour.

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Modeling of non-equilibrium phenomena in expanding flows by means of a collisional-radiative model

Physics of Plasmas ◽

10.1063/1.4810787 ◽

2013 ◽

Vol 20 (7) ◽

pp. 073501 ◽

Cited By ~ 40

Author(s):

A. Munafò ◽

A. Lani ◽

A. Bultel ◽

M. Panesi

Keyword(s):

Collisional Radiative Model ◽

Radiative Model ◽

Non Equilibrium

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Modeling of thermal and chemical non-equilibrium in a laser-induced aluminum plasma by means of a Collisional-Radiative model

Spectrochimica Acta Part B Atomic Spectroscopy ◽

10.1016/j.sab.2010.08.002 ◽

2010 ◽

Vol 65 (9-10) ◽

pp. 830-841 ◽

Cited By ~ 27

Author(s):

V. Morel ◽

A. Bultel ◽

B.G. Chéron

Keyword(s):

Aluminum Plasma ◽

Collisional Radiative Model ◽

Radiative Model ◽

Non Equilibrium

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Non L.T.E. Properties of Quasistationary Oxygen Plasmas

Zeitschrift für Naturforschung A ◽

10.1515/zna-1976-3-423 ◽

1976 ◽

Vol 31 (3-4) ◽

pp. 362-368 ◽

Cited By ~ 9

Author(s):

M. Cacciatore ◽

M. Capitelli

Keyword(s):

Excited States ◽

Cross Sections ◽

Ground State ◽

Radiative Recombination ◽

Local Thermodynamic Equilibrium ◽

Collisional Radiative Model ◽

Radiative Model ◽

Ionization Coefficients ◽

Selection Of ◽

The Continuum

The non L.T.E. (local thermodynamic equilibrium) properties of optically thin and thick quasistationary oxygen plasmas have been calculated for the temperature range k T = 0.5 - 1.5 eV and for the electron density interval 108 - 1016 cm-3 , by using the collisional-radiative model of Bates, Kingston and McWhirther. The results include1 the coefficients r0(i) and r1(i), which represent the contribution to the population density of the ith quantum level from the continuum and from the ground state, respectively2 the values of α and S, which are the collisional-radiative recombination and ionization coefficients, respectively. The accuracy of the present results is discussed in connection with the adopted plasma model and with the selection of the collisional cross sections for forbidden and allowed transitions. A discussion is also presented of the influence of the two low lying excited states of oxygen atoms (i.e. the states 2p41D, 2p41S) on the non L.T.E. properties of these plasmas. A satisfactory agreement is found with the calculations of Julienne et al. and with the experimental results of Jones.

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