Towards a general collisional radiative model

Collisional Radiative Models (CRMs) are a widely used tool in the modelling of plasmas. The results of such models appear as source terms in the particle and energy balances of plasma transport models. Usually such models calculate a partial Quasi Steady State Solution (QSSS). This means that the spatial and temporal relaxation of must excited state densities is neglected, which is valid for a broad variety of plasmas. Recently a new CRM has been developed which combines two interesting properties: * validity for a broad range of electron densities, as stepwise processes are taken into account; * the number of non-QSS levels can be chosen arbitrarily, generalising the concepts of the so-called coefficients of net ionisation and recombination. As a result of these properties it is possible to fully describe radiative transfer, while simultaneously the model is valid for higher electron densities, as stepwise processes can be taken into account. An application of the model is discussed in a second contribution to this conference ('Radiative Transfer in High-Current Ar-Hg Discharges, Van Dijk et el.). Other research groups are kindly invited to participate in this research

General treatment of the interplay between fluid and radiative transport phenomena in symmetric plasmas: the sulphur lamp as a case study

A general ray-trace method for calculating the effects of radiative transfer in a control volume (CV) fluid code is presented. The method makes use of the structured CV grid of the fluid code, and is suited for geometries with a point or axis of symmetry. In particular, the specific equations for spherical and cylindrical (without z dependence) configurations are developed. The application of this method to local thermal equilibrium (LTE) and non-LTE plasma models is discussed. Various opportunities for sacrificing precision for calculation speed are pointed out. As a case study, the effects of radiative transfer in a sulphur lamp are calculated. Since an LTE description of the molecular radiation yields a computed spectrum that differs significantly from a measured one, the possibility of a non-LTE vibrational distribution of the radiating S2-B state is investigated. The results indicate that the vibrational populations may be inversed

Semiclassical and quantum-mechanical descriptions of S2 molecular radiation

A semiclassical theory to calculate diatomic molecular radiation emission and absorption coefficients is presented in some detail. The theory is applied to the S2 {B} 3Su-¿X 3Sg- transition and the results are compared with a quantum-mechanical calculation. We show that disregarding fine structure, the semiclassical results compare very well with the average results of the quantum-mechanical theory. We conclude that the semiclassical theory is recommendable when fine structure is not important since it requires less detailed data about the molecular states and transition and its results can be computed faster

Modelling the spectrum of a high pressure sulphur discharge

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Modelling the spectrum of a high pressure sulphur discharge

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Radiative transfer in light source plasmas

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