Self-consistent coupling of DSMC method and SOLPS code for modeling tokamak particle exhaust

Bonelli, F.; Varoutis, S.; Coster, D.; Day, Christian; Zanino, Roberto

doi:10.1088/1741-4326/aa686f

Cited by 9 publications

(6 citation statements)

References 21 publications

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“…The DIVGAS code has been proved to be a reliable tool for the modeling of the neutral gas dynamics in the particle exhaust of tokamaks and stellarators in recent years [15,[26][27][28]. DIVGAS is a particle-based code, and its main kernel is based on the stochastic direct simulation Monte Carlo (DSMC) method proposed by G. A. Bird in 1963 [29] aiming in solving numerically the Boltzmann equation.…”

Section: Pumping Of D 2 and Seed Impuritiesmentioning

confidence: 99%

Divertor enrichment of recycling impurity species (He, N₂, Ne, Ar, Kr) in ASDEX Upgrade H-modes

Kallenbach,

Dux,

Henderson

et al. 2024

Nucl. Fusion

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Particle balance calculations are done for the seeding species N2, Ne, Ar, Kr as well as He with the aim of obtaining a realistic description of the divertor and core plasma impurity content. Experimental time traces of main plasma impurity densities are fitted by a single, time-independent parameter vz,in eff. This parameter represents the product of the impurity inward pinch in the pedestal, used for the description of gross fueling here, and the enrichment factor between the sub-divertor gas reservoir and the upstream separatrix. vz,in eff depends strongly on the first ionization energy as well as on the charge Z or mass of the impurity. The prevailing dependence of the enrichment values on the ionization energy suggests the importance of the relative impurity and deuterium ionization lengths in the divertor. Regression analysis of vz,in eff yields an expression for the impurity concentrations in the core and the divertor of ASDEX Upgrade which allows the prediction of the corresponding impurity densities and their divertor enrichment within a factor of 2 with only engineering parameters as input. A simple wall model has been introduced to take into account wall storage and release of impurities, e.g. for conditions of pre-loaded walls due to seeding in previous discharges. Wall effects are observed for all species considered, but wall storage turn out to be more important for N and He compared to Ne, Ar, Kr.Similar enrichment values are obtained for ELMy H-modes and EDA/QCE no-ELM regimes. A factor of approximately 1.4 reduction in enrichment is observed for divertor conditions for pronounced detachment with Ar and N2. The obtained analytical model for the core and sub-divertor impurity densities is well suited for integration into a discharge flight simulator or a real time state observer.

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Section: Pumping Of D 2 and Seed Impuritiesmentioning

confidence: 99%

Divertor enrichment of recycling impurity species (He, N₂, Ne, Ar, Kr) in ASDEX Upgrade H-modes

Kallenbach,

Dux,

Henderson

et al. 2024

Nucl. Fusion

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“…A detailed description of this method is omitted and the reader may consult the following publications [7][8][9][10][11] for further details. Here, only crucial simulation parameters are mentioned.…”

Section: The Divgas Code and Overall Considerations Of The Parallel I...mentioning

confidence: 99%

GPU acceleration of DEMO particle exhaust simulations

Varoutis¹,

Tantos²,

Day³

2021

Plasma Phys. Control. Fusion

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In this work we present an implementation of accelerating the calculation of neutral gas flow in a single-null DEMO divertor configuration on a graphics processing unit (GPU), using the DIVGAS (divertor gas simulator) code. For comparison purposes, various types of GPUs will be used, which include pure GPUs for scientific calculations as well as GPUs for gaming purposes. The computation accuracy of the DIVGAS code on GPUs has been validated with the corresponding CPU-based benchmark case. To evaluate the performance gains, the computing time on each GPU against its sequential CPU counterpart has been compared. The measured speedups show that the GPU can accelerate the execution of the DIVGAS code by a factor of 60. The speedup of the DIVGAS code scales linearly with the corresponding double precision peak performance of the GPU as well as the GPU memory bandwidth. The parallelization approach presented here significantly reduces the cost of DIVGAS simulations and has the potential to scale to large CPU/GPU clusters, which could enable future applications, which focus on even more complex 3D neutral flow problems. The accelerated version of the DIVGAS code on GPUs is considered to be a major breakthrough in the reduction of the needed computational time for fusion related applications.

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“…Since DSMC has been proven to be a reliable numerical tool to describe the behavior of rarefied gases in the divertor area, detailed description of this method here is omitted and the reader may refer to the following publications [7][8][9] for further details. In the present work only the essential aspects of the implementation are mentioned.…”

Section: Numerical Approach and Boundary Conditionsmentioning

confidence: 99%

Effect of neutral leaks on pumping efficiency in 3D DEMO divertor configuration

Varoutis

Igitkhanov

Day

et al. 2018

Fusion Engineering and Design

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In this paper we analyze the pumping efficiency of a generic 3D DEMO divertor configuration based on the size of inter-cassette gaps. Due to symmetry conditions we consider only one segment, which is composed by 3 divertor cassettes with the pumping port located at the bottom of the middle cassette and with four inter-cassette gaps. The width of intercassette gaps or the number of pumping ports is defined by the requirement to minimize the outflow of particles from the divertor to the plasma and hence, the highest possible pumping efficiency for the particle throughput, expected in DEMO, to be achieved. The DIVGAS code is used to perform a sensitivity analysis of the pumping efficiency, defined as a ratio of pumped particle flux to the particle throughput for different inter-cassette widths. The imposed neutral boundary conditions of pressure and temperature represent a moderate divertor pressure operating point. The analysis shows that for the reference case of 20 mm a reduction on the pumped flux of the order of 10% is observed when compared with the case of a completely sealed divertor. For smaller gaps the pumped flux reduction is found to be negligible, while for large values of the gap width the pumped flux reduction may reach the value of 20%. Furthermore, almost 80% of the incoming particles are moving towards the x-point, independent of the gap width. Therefore, the gap width does not influence the outflux towards the x-point, but only strongly affects the pumping efficiency. This analysis is meant to contribute to the ongoing DEMO divertor design efforts.

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Self-consistent coupling of DSMC method and SOLPS code for modeling tokamak particle exhaust

Cited by 9 publications

References 21 publications

Divertor enrichment of recycling impurity species (He, N₂, Ne, Ar, Kr) in ASDEX Upgrade H-modes

Divertor enrichment of recycling impurity species (He, N₂, Ne, Ar, Kr) in ASDEX Upgrade H-modes

GPU acceleration of DEMO particle exhaust simulations

Effect of neutral leaks on pumping efficiency in 3D DEMO divertor configuration

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Self-consistent coupling of DSMC method and SOLPS code for modeling tokamak particle exhaust

Cited by 9 publications

References 21 publications

Divertor enrichment of recycling impurity species (He, N2, Ne, Ar, Kr) in ASDEX Upgrade H-modes

Divertor enrichment of recycling impurity species (He, N2, Ne, Ar, Kr) in ASDEX Upgrade H-modes

GPU acceleration of DEMO particle exhaust simulations

Effect of neutral leaks on pumping efficiency in 3D DEMO divertor configuration

Contact Info

Product

Resources

About

Divertor enrichment of recycling impurity species (He, N₂, Ne, Ar, Kr) in ASDEX Upgrade H-modes

Divertor enrichment of recycling impurity species (He, N₂, Ne, Ar, Kr) in ASDEX Upgrade H-modes