The diffusion limit of ballistic transport in the scrape-off layer

Mänz, P.; Hufnagel, C.; Zito, A.; Carralero, D.; Griener, M.; Lunt, T.; Pan, O.; Passoni, M.; Tál, B.; Wischmeier, M.; Wolfrum, E.

doi:10.1063/1.5133839

Cited by 13 publications

(13 citation statements)

References 61 publications

(55 reference statements)

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“…The presence of a density shoulder at the outer SOL midplane in conditions of enhanced perpendicular transport, widely observed experimentally, was correctly reproduced by the performed simulations (figure 3). The performed SOLPS modelling could not provide details about turbulence and specific characteristics of filaments, although their presence might be quite well simulated through an increase of the particle diffusivity in the SOL [26]. Nevertheless, analyzing the plasma solutions allowed us to discuss the possible physical mechanisms relating shoulder formation and increase of transport.…”

Section: Perpendicular Transport and Density Shoulder Formationmentioning

confidence: 99%

Numerical modelling of an enhanced perpendicular transport regime in the scrape-off layer of ASDEX Upgrade

Zito

Wischmeier

Carralero

et al. 2021

Plasma Phys. Control. Fusion

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A desirable scenario for future fusion devices is one in which dissipative processes in the scrape-off layer (SOL) are maximized, aiming to detach the divertor plasma. The access to such a regime in current devices is thought to be correlated to the increase of the perpendicular particle transport in the SOL. In this work we investigated numerically how increasing perpendicular transport globally affects the SOL plasma through the SOLPS-ITER code package. For this we modelled one L-mode discharge, performed at the ASDEX Upgrade tokamak, trying to obtain the most accurate fit to the experimental data at the outer midplane. Studying the plasma solutions and analyzing the resulting momentum and power balances in the SOL allowed to characterize how enhancing perpendicular SOL transport leads to the experimentally observed phenomena, i.e. the formation of a density shoulder at the midplane and the partial detachment of the divertor plasma. The results suggest that strong momentum losses caused by the increase of transport are able to explain the qualitatively observed detachment in the modelled discharge. The concurrent enhanced ionization of neutrals resulting from divertor recycling, triggered by an increase of radial energy transport in the SOL, can be invoked as a cause for the shoulder formation.

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Section: Perpendicular Transport and Density Shoulder Formationmentioning

confidence: 99%

Numerical modelling of an enhanced perpendicular transport regime in the scrape-off layer of ASDEX Upgrade

Zito

Wischmeier

Carralero

et al. 2021

Plasma Phys. Control. Fusion

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“…Many transport codes, such as SOLPS, approximate turbulent transport via effective diffusion of particles (D an n and D an p ) and heat (κ e⊥ = χ an e n and κ i⊥ = χ an i n). The values of the anomalous transport coefficients are free parameters of the code, used to match the experimental radial profiles [49]. In our simulations the effects of the particle diffusion was evaluated varying D an n and D an p , while the heat diffusivity coefficients χ an e and χ an i were fixed at constant values.…”

Section: B25-eirene Coupled Simulationsmentioning

confidence: 99%

Simulations of Argon plasmas in the linear plasma device GyM with the SOLPS-ITER code

Sala

Tonello

Uccello

et al. 2020

Plasma Phys. Control. Fusion

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Edge plasma codes, such as SOLPS, are widely used to study plasma transport in tokamaks scrape-off layers (SOL). The possibility to apply these codes to non hydrogenic plasmas and to linear plasma devices (LPDs) is gaining the interests of the fusion community. These facilities play a pivotal role in plasma-material interaction (PMI) studies for future fusion devices and may allow to test the code capabilities both in terms of geometry and simulated plasma species. In this contribution, we apply the SOLPS-ITER code for the simulations of Argon plasmas in the medium-flux linear machine GyM. A sensitivity scan over the pumping efficiency, transport coefficients and absorbed electron power was done, performing B2.5-EIRENE coupled simulations. A quantitative analysis of the different flux contributions is provided through the use of a twopoint modelling. Comparison with experiments shows a promising qualitative and quantitative agreement, with the sole exception of the simulated neutrals pressure. Dedicated EIRENE standalone simulations were performed to investigate this issue, also highlighting the role of neutral-neutral elastic collisions at high values of the puffing intensity.

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“…It is able to reproduce realistic tokamak geometries and many magnetic configurations and, since its early versions, it was used as the standard tool for ITER design [14]. According to its modelling strategy, kinetic effects along B are accounted for through flux limiters [15], while the turbulent cross-field transport is modelled as a convective-diffusive process [16]. The possibility to simulate the problem in a self consistent way, albeit with some simplifying assumptions, comes at the price of a very high computational cost and, in many cases, not straightforward interpretation of its results.…”

Section: Introductionmentioning

confidence: 99%

A point plasma model for linear plasma devices based on SOLPS-ITER equations: application to helium plasma

et al. 2021

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Linear plasma devices represent an essential tool for nuclear fusion research, whereby understanding crucial aspects related to plasma-wall interactions or edge plasma behaviour. Simplified models are of great importance to complement and integrate experimental and simulation results of complex systems such as plasmas in linear machines, because they are fast and simple to employ. In this work, we present a global volume-averaged (0D) model for plasma investigation in linear machines. The 0D model equations are based on the space integration of the state of the art edge plasma model implemented in the SOLPS-ITER code. Comparisons between helium plasmas described with 2D simulations performed with SOLPS-ITER and with the 0D model highlight that contributions often neglected in tokamak edge models, e.g. electron-neutral excitation, may be relevant when describing weakly ionized plasmas in linear devices. The model is used to perform sensitivity studies with respect to several parameters and to analyse the time evolution of the system, leading to the identification of two relevant time scales governing the system. Lastly, a comparison of 0D results with experimental data from the linear device GyM is performed, showing satisfactory agreement. Our methods and results provide crucial interpretative keys in the investigation of the physics of edge plasmas.

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The diffusion limit of ballistic transport in the scrape-off layer

Cited by 13 publications

References 61 publications

Numerical modelling of an enhanced perpendicular transport regime in the scrape-off layer of ASDEX Upgrade

Numerical modelling of an enhanced perpendicular transport regime in the scrape-off layer of ASDEX Upgrade

Simulations of Argon plasmas in the linear plasma device GyM with the SOLPS-ITER code

A point plasma model for linear plasma devices based on SOLPS-ITER equations: application to helium plasma

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