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 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The system of coupled nonlinear Saha equations supplemented by electroneutrality and conservation of nuclei for complex plasma mixtures is reformulated into a reduced form, which allows the development of an efficient numerical algorithm to solve the set of nonlinear equations. The efficient algorithm is based on the solution of an equivalent single transcendental equation. Nonideality corrections have been taken into consideration in terms of depression of ionization potentials and truncated partition functions. Implementing this simple efficient methodology simplifies the problem and considerably reduces the computational effort needed to compute the detailed plasma composition for different cases. The algorithm is analytically known to be safe, fast, and efficient. It also shows no numerical instabilities, no convergence problems, and no accuracy limitations or lack of change problems, which have been reported in the literature. A nontrivial sample problem has been worked in detail showing the usefulness of the method for applied and industrial plasma physicists. Effects of the nonideality corrections and the exclusion of excited states are quantified and presented. A criterion for the validity of the assumption of local thermodynamic equilibrium is applied to the results from the sample problem to show the region of the temperature-density phase space over which the assumption is valid.
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PMID:Reduced formulation and efficient algorithm for the determination of equilibrium composition and partition functions of ideal and nonideal complex plasma mixtures. 1499 84

A physical model based on a Monte Carlo approach is proposed to calculate the ionization dynamics of hot-solid-density plasmas within particle-in-cell (PIC) simulations, and where the impact (collision) ionization (CI), electron-ion recombination (RE), and ionization potential depression (IPD) by surrounding plasmas are taken into consideration self-consistently. When compared with other models, which are applied in the literature for plasmas near thermal equilibrium, the temporal relaxation of ionization dynamics can also be simulated by the proposed model. Besides, this model is general and can be applied for both single elements and alloys with quite different compositions. The proposed model is implemented into a PIC code, with (final) ionization equilibriums sustained by competitions between CI and its inverse process (i.e., RE). Comparisons between the full model and model without IPD or RE are performed. Our results indicate that for bulk aluminium at temperature of 1 to 1000 eV, (i) the averaged ionization degree increases by including IPD; while (ii) the averaged ionization degree is significantly over estimated when the RE is neglected. A direct comparison from the PIC code is made with the existing models for the dependence of averaged ionization degree on thermal equilibrium temperatures and shows good agreements with that generated from Saha-Boltzmann model and/or FLYCHK code.
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PMID:Monte Carlo approach to calculate ionization dynamics of hot solid-density plasmas within particle-in-cell simulations. 2829 47

A chemical model is proposed for a dusty plasma consisting of electrons, ions, neutrals, and positively charged dust particles all being at thermodynamic equilibrium. An expression is derived for the Helmholtz free energy, which comprises the ideal part, taking into account the charge of dust particles, and the excess part, evaluated in the framework of the self-consistent chemical model [Phys. Rev. E 83, 016405 (2011)PLEEE81539-375510.1103/PhysRevE.83.016405]. The ionization potential depression for a dust-free partially ionized hydrogen is analytically evaluated for weakly and strongly ionized states to consistently account for the presence of charged and neutral components. An ad hoc interpolation of the ionization potential depression, valid across the whole ionization region, is put forward and subsequent solution of the generalized Saha equation is found to be in a perfect agreement with exact calculations. Minimization of the Helmholtz free energy of dusty plasmas provides the number densities of free electrons, free ions, neutrals, and the dust electric charge as well. Based on consideration of weakly and strongly ionized states, a straightforward comparison is made of the ionization equilibrium in a partially ionized plasma with and without dust particles to demonstrate that at thermal equilibrium positively charged dusts are responsible for an increase in the number density of free electrons and a decrease in the number density of free ions. It is analytically proved that nonideality effects result in a growth of the number densities of free electrons and ions by obtaining the so-called electron and proton ionization potential depressions. Electric charge of dust particles is systematically studied as a full plasma component rather than considering a detailed balance of the electron and ion fluxes on the surface of a solitary dust grain.
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PMID:Influence of dust particles on ionization equilibrium in partially ionized plasmas. 3268 40