Modélisation numérique de la couche limite des plasmas de fusion et de sa perméabilité aux ions lourds produits par l’interaction plasma-paroi : vers l’élaboration d’un modèle prédictif à partir des expériences sur le tokamak WEST (Thèse 2021 - 2024)
Activités
Plasma
Fusion magnétique
Ions lourds
Modélisation numérique
Couche limite
Publications scientifiques au M2P2
2024
Stefano Di Genova, Alberto Gallo, Luca Cappelli, Nicolas Fedorczak, Hugo Bufferand, et al.. Global analysis of tungsten migration in WEST discharges using numerical modelling. Nuclear Fusion, 2024, ⟨10.1088/1741-4326/ad82f9⟩. ⟨hal-04739577⟩ Plus de détails...
Plasma discharges in the tungsten (W) Environment Steady-state Tokamak (WEST) are strongly impacted by W contamination. In WEST experiments, due to W contamination, the power radiated in the plasma (PRad) is on average, around 50% of the total power injected into the plasma (PTOT). Furthermore, this radiated power fraction (fRad) is almost insensitive to plasma conditions. The causes behind this experimental trend are not fully understood. In this contribution, a 3D numerical model is used to analyze the W migration in the WEST boundary plasma in different plasma scenarios. The WEST experimental database is sampled to obtain a scan of simulation input parameters. These parameters mimic the WEST plasma conditions over a chosen experimental campaign. The simulation results are compared to WEST diagnostics measurements (reflectometry, Langmuir probes, and visible spectroscopy) to verify that the simulated plasma conditions are representative of the WEST database. The W contamination trend is analysed: the W density (nW) strongly decreases when the radial distance between the separatrix and WEST antennas (Radial Outer Gap, ROG) increases. On the other hand, at a given ROG, nW increases proportionally with the power entering the scrape-off layer (PSOL). PRad is estimated with a simple 0D model. For a fixed ROG, fRad is not sensitive to plasma conditions. These trends are qualitatively and, at times, quantitatively comparable to what is observed in WEST experiments: the simulated trends are related to the poorly screened W influx caused by the erosion of the main chamber Plasma-Facing Components (PFCs). Thus, this numerical analysis suggests a possible interpretation of WEST experimental trends.
Stefano Di Genova, Alberto Gallo, Luca Cappelli, Nicolas Fedorczak, Hugo Bufferand, et al.. Global analysis of tungsten migration in WEST discharges using numerical modelling. Nuclear Fusion, 2024, ⟨10.1088/1741-4326/ad82f9⟩. ⟨hal-04739577⟩
L. Cappelli, N. Fedorczak, J. P. Gunn, S. Di Genova, J. Guterl, et al.. Study of the erosion and redeposition of W considering the kinetic energy distribution of incident ions through a semi-analytical model. Plasma Physics and Controlled Fusion, 2023, 65 (9), pp.095001. ⟨10.1088/1361-6587/ace282⟩. ⟨hal-04190861⟩ Plus de détails...
In today’s nuclear fusion devices, erosion of high-Z metallic plasma-facing materials (PFMs) is mainly caused by physical sputtering. That is, by the exchange of energy between plasma ions and the atoms in the walls. In most of the numerical codes currently in use impinging plasma is approximated as a fluid. By averaging the incident particles’ energy distribution the high-energy population of the eroded material is underestimated. For heavy materials such as W, high-energy eroded particles tend to ionize far from the wall and they are less affected by the sheath electric field hence, not being attracted back to the wall, they have a higher chance to contaminate the core plasma. This could in turn result in an underestimation of the net erosion sources. In this work, a semi-analytical model was developed to include the energy distribution of the incident particles. Then, by Monte Carlo method, the net erosion of tungsten from a smooth PFM was calculated. The results show that the kinetic description in energy is important only for incident particles ionized once. For instance, it is particularly important for plasma ions such as Deuterium. It is seen that Deuterium contribution to the W net sources is not always negligible if compared to light impurities or to tungsten self-sputtering in the range of plasma parameters tested. Finally, results show that the difference between the fluid and kinetic models becomes more pronounced for high-screening plasma conditions.
L. Cappelli, N. Fedorczak, J. P. Gunn, S. Di Genova, J. Guterl, et al.. Study of the erosion and redeposition of W considering the kinetic energy distribution of incident ions through a semi-analytical model. Plasma Physics and Controlled Fusion, 2023, 65 (9), pp.095001. ⟨10.1088/1361-6587/ace282⟩. ⟨hal-04190861⟩
S. Di Genova, G. Ciraolo, A. Gallo, J. Romazanov, N. Fedorczak, et al.. First 3D modeling of tungsten erosion and migration in WEST discharges adopting a toroidally non-symmetric wall geometry. Nuclear Materials and Energy, 2023, 34, pp.101340. ⟨10.1016/j.nme.2022.101340⟩. ⟨hal-03988791⟩ Plus de détails...
Numerical analyses are a key tool to investigate tungsten (W) sources and contamination in W Environment steady-state tokamak (WEST) plasma discharges. Modelling activity was performed in order to study W erosion and migration at WEST plasma-facing components (PFCs), using for the first time a toroidally asymmetric wall geometry provided by toroidally localized objects representing WEST outer limiter or antennae. 3D non-axisymmetric SOLEDGE transport simulations were performed with simplifying assumptions (pure Deuterium plasma, fluid model for neutrals) to reproduce WEST boundary plasma, and used as background for ERO2.0 simulations modelling W erosion, re-deposition, and migration. On the sides of the toroidally localized limiters/antennae, two thin W stripes were considered in order to model WEST W antennae protections. Simulations suggest antennae protections contribution to dominate W contamination in the considered simulations settings, highlighting the need of further analyses with different configurations using this kind of tools.
S. Di Genova, G. Ciraolo, A. Gallo, J. Romazanov, N. Fedorczak, et al.. First 3D modeling of tungsten erosion and migration in WEST discharges adopting a toroidally non-symmetric wall geometry. Nuclear Materials and Energy, 2023, 34, pp.101340. ⟨10.1016/j.nme.2022.101340⟩. ⟨hal-03988791⟩
Ivan Kudashev, Anna Medvedeva, Manuel Scotto D’abusco, Nicolas Fedorszak, Stefano Di Genova, et al.. Development of a set of synthetic diagnostics for the confrontation between 2D transport simulations and WEST tokamak experimental data. Applied Sciences, 2022, 12 (19), pp.9807. ⟨10.3390/app12199807⟩. ⟨hal-03982630⟩ Plus de détails...
Transport codes are frequently used for describing fusion plasmas with the aim to prepare tokamak operations. Considering novel codes, such as SolEdge3X-HDG, synthetic diagnostics are a common technique used to validate new models and confront them with experimental data. The purpose of this study is to develop a set of synthetic diagnostics, starting from bolometer and visible cameras for the WEST tokamak, in order to compare the code results with the experimental data. This research is done in the framework of Raysect and Cherab Python libraries. This allows us to process various synthetic diagnostics in the same fashion in terms of 3D ray tracing with volume emitters developed specifically for fusion plasmas. We were able to implement the WEST tokamak model and the design of bolometer and visible cameras. Synthetic signals, based on full-discharge WEST plasma simulation, were used for to compare the SolEdge3X-HDG output plasma with experimental data. The study also considers the optical properties of the plasma-facing components (PFCs) and their influence on the performance of diagnostics. The paper shows a unified approach to synthetic diagnostic design, which will be further extended to cover the remaining diagnostics on the WEST tokamak.
Ivan Kudashev, Anna Medvedeva, Manuel Scotto D’abusco, Nicolas Fedorszak, Stefano Di Genova, et al.. Development of a set of synthetic diagnostics for the confrontation between 2D transport simulations and WEST tokamak experimental data. Applied Sciences, 2022, 12 (19), pp.9807. ⟨10.3390/app12199807⟩. ⟨hal-03982630⟩
S. Di Genova, A. Gallo, N. Fedorczak, H. Yang, G. Ciraolo, et al.. Modelling of tungsten contamination and screening in WEST plasma discharges. Nuclear Fusion, 2021, 61 (10), pp.106019. ⟨10.1088/1741-4326/ac2026⟩. ⟨hal-03380329⟩ Plus de détails...
The WEST experiment is currently operating with tungsten plasma-facing components and testing ITER-like divertor monoblocks. In order to support WEST experiments interpretation, numerical analyses were carried out. Starting from WEST experimental data, realistic background plasma conditions were reproduced through SolEdge-EIRENE and used as input for ERO2.0 simulations to investigate tungsten migration. Tungsten contamination due to the different plasma-facing components was modelled under different plasma conditions, highlighting a non-negligible contribution of tungsten coming from the tokamak main chamber. Tungsten penetration factor was computed and used as an indication for tungsten screening by the background plasma at the different tokamak plasma-facing components. Simulations showed the main chamber components to be very weakly screened. Light impurities charge was showed to influence not only tungsten sputtering, but also its probability to enter the confined plasma. Simulations results indicated that even when the tungsten source is not heavily influenced by self-sputtering, contamination of the confined plasma can be strongly impacted by it in low density background plasma conditions. Finally, a one-to-one comparison between tungsten visible spectroscopy at the lower divertor from experimental data and from synthetic diagnostics was performed, showing that it is possible to reproduce a realistic lower divertor signal following experimental evidence on light impurities asymmetry between the targets.
S. Di Genova, A. Gallo, N. Fedorczak, H. Yang, G. Ciraolo, et al.. Modelling of tungsten contamination and screening in WEST plasma discharges. Nuclear Fusion, 2021, 61 (10), pp.106019. ⟨10.1088/1741-4326/ac2026⟩. ⟨hal-03380329⟩
G. Ciraolo, S. Di Genova, H. Yang, A. Gallo, N. Fedorczak, et al.. INTERPRETATIVE MODELING OF IMPURITY TRANSPORT AND TUNGSTEN SOURCES IN WEST BOUNDARY PLASMA. Nuclear Fusion, 2021, 61 (12), pp.126015. ⟨10.1088/1741-4326/ac2439⟩. ⟨hal-03420146⟩ Plus de détails...
The contamination of core plasma by high-Z impurities, especially tungsten (W), is the main reason of very high level of radiated power in WEST experiments. Intrinsic light impurities, mainly oxygen and carbon, play a dominant role in the sputtering of W on plasma facing components. In this contribution, we present a detailed analysis of WEST experiments supported by numerical modeling performed with the transport code SOLEDGE-EIRENE providing a clear picture of light impurities transport and poloidal distribution. Moreover, making use of SOLEDGE-ERO2.0 simulations, possible strategies to reduce core contamination due to W penetration are presented. .
G. Ciraolo, S. Di Genova, H. Yang, A. Gallo, N. Fedorczak, et al.. INTERPRETATIVE MODELING OF IMPURITY TRANSPORT AND TUNGSTEN SOURCES IN WEST BOUNDARY PLASMA. Nuclear Fusion, 2021, 61 (12), pp.126015. ⟨10.1088/1741-4326/ac2439⟩. ⟨hal-03420146⟩
