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A coarse-grained kinetic equation for neutral particles (atoms, molecules) in magnetized fusion plasmas, valid on time scales large compared to the turbulence correlation time, is presented. This equation includes the effects of plasma density fluctuations, described by gamma statistics, on the transport of neutral particles. These effects have so far been neglected in plasma edge modeling, in spite of the fact that the amplitude of fluctuations can be of order unity. Density fluctuations are shown to have a marked effect on the screening of neutrals and on the spatial localization of the ionization source, in particular at high density. The coarse-grained equations obtained in this work are readily implemented in edge code suites currently used for fusion plasma analysis and future divertor design (ITER, DEMO). [ABSTRACT FROM AUTHOR]

The effect of fluctuations of the electron temperature on the population kinetics of a reduced atomic system is investigated in the case of a low density plasma, where the coronal approximation can be used. An exponential correlation function is assumed for the electron temperature fluctuations. A resonance of the average population as a function of the correlation time is observed and analyzed. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the role of turbulent fluctuations on line shape formation in optically thin plasmas. A general expression, valid if the turbulent scales are much larger than the atomic scales, is obtained for the profile measured using a passive spectroscopy set up. Well-known limiting cases for Doppler and Stark broadening are identified. Then, the role of temperature fluctuations on Doppler line shapes, and the effect of density fluctuations on Stark broadened lines in the quasi-static regime are investigated. [Copyright &y& Elsevier]

Abstract: Ion dynamics is revisited in the presence of a magnetic field. This problem is of interest for the characterization of the ITER divertor plasmas, where Zeeman–Stark line shapes are both a diagnostic tool and an ingredient in the transport codes used for radiative transfer simulations. Comparisons between ab initio simulations of Zeeman–Stark profiles and calculations performed using the computationally efficient frequency fluctuation model are presented for the Lyman α and Balmer α lines. [Copyright &y& Elsevier]

Abstract: The population balance of atoms or ions in an edge plasma is calculated in the presence of fluctuating density or temperature. We have used a stochastic model taking advantage of the knowledge of the plasma parameter statistical properties, and assuming a stepwise constant stochastic process for the fluctuating variable. The model is applied to simplified atomic systems such as three level hydrogen atoms or the ionization balance of carbon affected by electronic temperature or density fluctuations obeying a gamma PDF, and an exponential waiting time distribution. [Copyright &y& Elsevier]

The transport of neutral particles in turbulent plasmas is addressed from the prospect of developing coarse-grained transport models which can be implemented in code suites like B2-EIRENE, currently used for designing the ITER divertor. The statistical properties of turbulent fluctuations are described by a multivariate Gamma distribution able to retain space and time correlations through a proper choice of covariance function. We show that in the scattering free case, relevant for molecules and impurity atoms, the average neutral particle density obeys a Boltzmann equation with an ionization rate renormalized by fluctuations. This result lends itself to a straightforward implementation in the EIRENE Monte Carlo solver for neutral particles. Special emphasis is put on the inclusion of time correlations, and in particular on the ballistic motion of coherent turbulent structures. The role of these time dependent effects is discussed for D2 molecules and beryllium atoms. The sensitivity of our results to the assumptions on the statistical properties of fluctuations is investigated. [ABSTRACT FROM AUTHOR]

Abstract: A novel approach to the modeling of atomic populations in turbulent plasmas is applied to ionization–recombination balance calculations. Fluctuations of the fluid parameters are retained using a time-dependent statistical approach, suitable for cases where the turbulence characteristic times are of the same order as or smaller than the typical atomic relaxation times. We show that the populations are sensitive to the shape of the autocorrelation function of the fluctuations. An illustration is proposed through an ideal two-level system forced by non-Markovian temperature fluctuations. [Copyright &y& Elsevier]

Abstract: The effect of turbulence on the transport of neutral species (atom, molecules) in plasmas is investigated. A stochastic model relying on a multivariate gamma distribution is used to describe turbulent fluctuations. This model incorporates several important known features of Scrape-off-Layer turbulence, and has been implemented in the EIRENE Monte Carlo code. The effect of fluctuations on the neutral density, ionisation source and Balmer α radial profiles are investigated. Two important control parameters are identified, namely the ratio of the neutral mean free path to the size of turbulent structures, and the ratio of recycling time scales to the turbulent times. [Copyright &y& Elsevier]