A reduced model of neutral-plasma interactions in the edge and scrape-off-layer: Verification comparisons with kinetic Monte Carlo simulations

Russell, D. A.; Myra, J. R.; Stotler, D.P.

doi:10.1063/1.5081670

Cited by 18 publications

(14 citation statements)

References 39 publications

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“…Numerous SOL turbulence models and codes are now being extended to include these features. [92][93][94][95][96][97][98][99][100] The statistical framework with super-position of filaments can be used for analysis and interpretation of simulation results in these more advanced models, similar to what has been done here and previously for experimental measurements. As such, this work sets a new standard for validation of turbulence simulation codes.…”

Section: Discussionmentioning

confidence: 84%

Numerical turbulence simulations of intermittent fluctuations in the scrape-off layer of magnetized plasmas

Decristoforo,

Theodorsen,

Omotani

et al. 2021

Preprint

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Intermittent fluctuations in the boundary of magnetically confined plasmas are investigated by numerical turbulence simulations of a reduced fluid model describing the evolution of the plasma density and electric drift vorticity in the two-dimensional plane perpendicular to the magnetic field. Two different cases are considered, one describing resistive drift waves in the edge region and another including only the interchange instability due to unfavorable magnetic field curvature in the scrape-off layer. Analysis of long data time series obtained by single-point recordings are compared to predictions of a stochastic model describing the plasma fluctuations as a super-position of uncorrelated pulses. For both cases investigated, the radial particle density profile in the scrape-off layer is exponential with a radially constant scale length. The probability density function for the particle density fluctuations in the far scrape-off layer has an exponential tail. Radial motion of blob-like structures leads to large-amplitude bursts with an exponential distribution of peak amplitudes and the waiting times between them. The average burst shape is well described by a two-sided exponential function. The frequency power spectral density of the particle density is simply that of the average burst shape and is the same for all radial positions in the scrape-off layer. The fluctuation statistics obtained from the numerical simulations are in excellent agreement with recent experimental measurements on magnetically confined plasmas. The statistical framework defines a new validation metric for boundary turbulence simulations.

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Section: Discussionmentioning

confidence: 84%

Numerical turbulence simulations of intermittent fluctuations in the scrape-off layer of magnetized plasmas

Decristoforo,

Theodorsen,

Omotani

et al. 2021

Preprint

View full text Add to dashboard Cite

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“…2005; Fundamenski et al. 2007; Russell, Myra & Stotler 2019). The main quantities are obtained by integrating the distribution function in the velocity space.…”

Section: The Modelmentioning

confidence: 99%

“…In the fluid approach, the plasma can be described by considering a few moments of the particle distribution function, leading to a set of fluid equations, such as the ones derived by Braginskii in 1965(Braginskii 1965Garcia et al 2005;Fundamenski et al 2007;Russell, Myra & Stotler 2019). The main quantities are obtained by integrating the distribution function in the velocity space.…”

Section: The Modelmentioning

confidence: 99%

Simulation campaign of the turbulent diffusion at the edge of fusion devices

Scarivaglione

Valentini²,

Servidio³

2023

J. Plasma Phys.

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The understanding of cross-field transport is crucial for optimizing the properties of magnetic confinement in fusion devices. In this work, a two-dimensional, simplified model is used to study the turbulent dynamics in the region of the scrape-off layer. The numerical model, based on the reduced Braginskii equations, is able to describe the formation and the evolution of blob-like structures. The dynamics has been investigated by using both classical Eulerian analysis and the Lagrangian approach, by varying the ambient conditions of the plasma. The major goals are (i) a detailed and systematic study of turbulence by varying the plasma jump conditions in the edge tokamaks plasmas and (ii) a Lagrangian diffusion study of the edge turbulence by using an appropriate Braginskii model. It has been found that both the magnetic shear and the plasma mean profiles of density and temperature are crucial for setting the properties of the transport. By following fluid tracers, diffusive transients for the radial transport are observed, at length scales larger than the typical blob size. This work is relevant for the comprehension of the turbulent transport at tokamaks edges.

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“…The profiles at the plasma edge and Scrape-Off Layer (SOL) regions determine the exhaust of particles and heat from the core and are central in regulating the machine performance [1]. The sources at the colder plasma boundary originate largely from the interactions with the neutral atoms and molecules, and the impact of the interactions on the plasma transport is subject to current attention in both experiments [2,3] and simulations [4][5][6][7][8][9][10][11][12]. In particular, such effects as fuelling, divertor detachment [1,[13][14][15] and SOL density shoulder formation [2,[16][17][18][19][20], depend on the plasma-neutral interactions.…”

Section: Introductionmentioning

confidence: 99%

On the interpretation of kinetic effects from ionization in fluid models and its impact on filamentary transport

2023

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In regions where a plasma is not fully ionized, such as the edge and scrape-off layer (SOL) regions in a tokamak, the charged particles may be subject to strong sources from interactions with neutral atoms and molecules. Such sources, e.g., from electron impact ionization, can introduce kinetic effects, as the ionized particles may have flow velocity and temperature different from that of the main species. If treated in the conventional fluid picture, this kinetic effect emerges as a frictional heating term. In this paper, the physics of this term is discussed, both for un-magnetized and magnetized plasmas. The fluid source terms are mapped back to the kinetic sources to provide a consistent picture for future model comparison. In the limits of low and high ratios between the rates of thermalization and ionization, a multi-ion species drift-fluid model is applied to assess the impact of this kinetic effect on SOL drift-plane plasma transport. This is done by modeling a seeded blob where the ions follow either a single- or double-Maxwellian velocity distribution function (VDF). It is found that the robustness of the magnetized plasma VDF in the drift-plane and the limited effect on the vorticity source ensure that the impact of kinetic effects on the perpendicular blob evolution is small, even in the limit of high ionization to thermalization rate ratio, where kinetic effects to the ion VDF are significant.

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A reduced model of neutral-plasma interactions in the edge and scrape-off-layer: Verification comparisons with kinetic Monte Carlo simulations

Cited by 18 publications

References 39 publications

Numerical turbulence simulations of intermittent fluctuations in the scrape-off layer of magnetized plasmas

Numerical turbulence simulations of intermittent fluctuations in the scrape-off layer of magnetized plasmas

Simulation campaign of the turbulent diffusion at the edge of fusion devices

On the interpretation of kinetic effects from ionization in fluid models and its impact on filamentary transport

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