Collisional radiative models with multiple transport-sensitive levels - application to high electron density mercury discharges

Abstract

In this paper some of the basic concepts in collisional radiative modelling of plasmas will be generalized. A mathematical framework is presented which is suitable for systems with an arbitrary number of transport sensitive and quasi-steady or local chemistry states. The mathematical formulation presented here leads to straightforward extensions of quantities which have been previously introduced for systems in which only the atom and ion ground states were dealt with explicitly. These are the net coefficients of ionization and recombination, the effective specific emission coefficients, and the relative overpopulation coefficients. For a given set of transport-sensitive densities these quantities can be used to calculate the particle and radiation source terms and the atomic state distribution function. Furthermore the use of matrix-vector calculus has led to concise, insightfull, yet general expressions. And although some explicit references will be made to plasmas which are governed primarily by processes involving electrons, most of the theory presented here can be carried over to other systems without great difficulty. As an example, a collisional radiative model for mercury will be presented for discharges with electron temperatures between 0.75 eV and 2 eV and electron densities between 1018 m-3 and 1020 m-3. In the current model six transport-sensitive levels have been assumed. Another 13 excited mercury states are taken into account implicitly; ladderlike excitation and ionization will be shown to be of major importance for discharges in this parameter range. The model allows the incorporation of heavy-particle reactions and a full treatment of the transfer of resonant radiation.

The plasma modelling toolkit Plasimo

“…An early version of the Plasimo-CRM was published in [84] and is publicly available. We recommend interested parties to contact the Plasimo team instead to discuss the availability of a more recent version of this code, which contains the generalization of the formalism that has been discussed in [85]. The present text contains a summary of the latter paper, and extends some of the concepts discussed therein.…”

“…The second term contains the other direct transitions between the t-states. As discussed in [85], this source contribution can host the resonant radiative transitions, for which an external radiation transport may be required. This requires that the level from which the radiation originates is marked as transport sensitive.…”

“…An example of such a process is dissociative recombination of molecular ions that leads to the production of excited states. This type of process was excluded in the analysis in [85]. Equation (33) provides a recipe for dealing with such processes: it simply requires that the relevant elements of the matrix M lt M −1 ll are stored.…”

“…For more details about the theory that underlies this technique and the calculation of the radiative and energy loss terms, we refer to [85]. References [85,87] demonstrate an application of this technique to mercury plasma with high degrees of ionization.…”

Mn-Based Catalysts for Post Non-Thermal Plasma Catalytic Abatement of VOCs: A Review on Experiments, Simulations and Modeling

“…The most used models are collisional radiative models (CRM), global plasma models (GPM), and reaction exploration models (REM) [135]. The tasks of CRM are threefold as follows: (i) to calculate the atomic state distribution function (ASDF), (ii) the source terms for the energy equation, and (iii) the effective conversion rates between transport sensitive levels [140].…”