Effects of turbulent fluctuations with prescribed statistics on passive neutral particle transport in plasmas

Marandet, Y.; Mekkaoui, A.; Reiter, D.; Boerner, P.; Génésio, P.; Rosato, J.; Capes, H.; Catoire, F.; Koubiti, M.; Godbert‐Mouret, L.; Stamm, R.

doi:10.1088/0741-3335/53/6/065001

Cited by 18 publications

(21 citation statements)

References 26 publications

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“…This corresponds to coherent structures moving towards the wall, i.e., in a direction opposite to that of recycling neutrals in the radial direction. v sx ¼ 0 corresponds to the case investigated in previous works, 19,22,23 and v sx ¼ À1 km/s is a realistic value. 9 For D 2 molecules we have s d v 0 =k x ¼ 0:6, while for Be atoms s d v 0 =k x ¼ 3 (the corresponding horizontal lines are plotted on Fig.…”

Section: Application: the Effects Of Structure Propagationmentioning

confidence: 86%

“…(A5) of Ref. 22. The fact that the cumulant expansion has a finite convergence radius is related to the choice of the Gamma statistics (in other words, the cumulant expansion of the Gamma distribution has a finite convergence radius) and manifests itself in other works dealing with stochastic modeling of plasma density fluctuations (see Eqs.…”

Section: A Role Of the N-point Correlation Functionsmentioning

confidence: 89%

“…19,22,23 As a result, in typical SOL conditions the effects of fluctuations on fuel atoms (hydrogen isotopes) can be safely ignored. This is true even for fuel atoms thermally released from the wall, because of resonant charge exchange.…”

Section: Model Assumptionsmentioning

confidence: 99%

“…-1 , where the value of -1 follows from Szeg€ o's theorem on Toeplitz matrices. 22,42 For the covariance given by Eq. (15)…”

Section: Coarse-grained Transport Equationmentioning

confidence: 99%

“…For the multivariate Log-normal case, the only available option at the present time is to rely on sampling methods, that is, solving the Boltzmann equation for a large number of realizations of the density field. This approach can either rely on brute force, by Cholesky decomposition of the covariance matrix, 22,23 or on more sophisticated methods, e.g., Karhunen-Loève decomposition for the plasma density combined to stochastic collocation for the density of neutrals (the covariance of which is not known a priori). 52…”

Section: -9mentioning

confidence: 99%

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A coarse-grained transport model for neutral particles in turbulent plasmas

et al. 2012

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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 D 2 molecules and beryllium atoms. The sensitivity of our results to the assumptions on the statistical properties of fluctuations is investigated.

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Section: Application: the Effects Of Structure Propagationmentioning

confidence: 86%

Section: A Role Of the N-point Correlation Functionsmentioning

confidence: 89%

Section: Model Assumptionsmentioning

confidence: 99%

“…-1 , where the value of -1 follows from Szeg€ o's theorem on Toeplitz matrices. 22,42 For the covariance given by Eq. (15)…”

Section: Coarse-grained Transport Equationmentioning

confidence: 99%

Section: -9mentioning

confidence: 99%

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A coarse-grained transport model for neutral particles in turbulent plasmas

et al. 2012

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Modeling of Radiation Transport in Fluctuating Edge Plasmas: A Statistical Approach

Rosato

Mekkaoui

Marandet

et al. 2012

Contrib. Plasma Phys.

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The radiation due to atomic lines in the tokamak edge and divertor can be strongly coupled to the plasma dynamics. Self-consistent (charged particle -atom -photon) simulations carried out for ITER conditions with the transport code B2-EIRENE have indicated modifications of the effective ionization rate induced by photon absorption effects. Up to now, all of the investigations done so far were made assuming a plasma background whose typical spatial variation scales are much larger than the radiation transport scale. In this paper, we examine the validity of this approximation within an effective transport model, relying on a statistical parameterization of the turbulent fluctuations. The model is inspired from the quasilinear theory used for plasma turbulence and assumes a small ratio l turb /l mfp between the turbulence correlation length and the photon mean free path. We apply the model to calculations of the penetration of a radiation pencil in an optically thick turbulent plasma. The validity of this model for intermediate l turb /l mfp is next discussed through comparison to a "model-coefficient" approach, widely used in problems involving linear stochastic differential equations and suitable for arbitrary turbulence correlation length.

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Transport of Neutrals in Scrape‐Off Layer Plasmas: Autoregressive Beta Process to Describe Plasma Density and Temperature Fluctuations

Mekkaoui¹,

Marandet²,

Rosato³

et al. 2012

Contrib. Plasma Phys.

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Improving the description of the far scrape-off layer (SOL) in current edge code suites such as SOLPS is the subject of current efforts, given the importance of main chamber plasma wall interactions (first wall recycling and sputtering) in the design and operation of tokamaks. One of the specific features of the far SOL is the large amplitude of turbulent fluctuations. Neutral particles (atom and molecules) are affected by these fluctuations through the rates of atomic physics processes. In accordance with experimentally measured PDF (probability density function) for both the plasma density and temperature fluctuations, ne and Te are modeled using a Beta PDF. Space and time correlations are accounted for by using an autogressive process. The effects of fluctuations on the neutral atoms penetration depth, as well as on the beryllium sputtering yield are discussed.

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Effects of turbulent fluctuations with prescribed statistics on passive neutral particle transport in plasmas

Cited by 18 publications

References 26 publications

A coarse-grained transport model for neutral particles in turbulent plasmas

A coarse-grained transport model for neutral particles in turbulent plasmas

Modeling of Radiation Transport in Fluctuating Edge Plasmas: A Statistical Approach

Transport of Neutrals in Scrape‐Off Layer Plasmas: Autoregressive Beta Process to Describe Plasma Density and Temperature Fluctuations

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