Simulations de Hautes performances pour les plasmas de tokamak (thèse: 2012 - 2015)
actuellement en Post-Doc
Activités
Plasmas de tokamak, plasma de bord
Transport et Turbulence
Sonde de Langmuir
Instabilité d'interchange
Modélisation, simulation numérique
Publications scientifiques au M2P2
2017
Davide Galassi, P. Tamain, H. Bufferand, Guido Ciraolo, Ph. Ghendrih, et al.. Drive of parallel flows by turbulence and large-scale E × B transverse transport in divertor geometry. Nuclear Fusion, 2017, 57 (3), pp.036029. ⟨10.1088/1741-4326/aa5332⟩. ⟨hal-01592945⟩ Plus de détails...
The poloidal asymmetries of parallel flows in edge plasmas are investigated by the 3D fluid turbulence code TOKAM3X. A diverted COMPASS-like magnetic equilibrium is used for the simulations. The measurements and simulations of parallel Mach numbers are compared, and exhibit good qualitative agreement. Small-scale turbulent transport is observed to dominate near the low field side midplane, even though it co-exists with significant large-scale cross-field fluxes. Despite the turbulent nature of the plasma in the divertor region, simulations show the low effectiveness of turbulence for the cross-field transport towards the private flux region. Nevertheless, a complex pattern of fluxes associated with the average field components are found to cross the separatrix in the divertor region. Large-scale and small-scale turbulent E x B transport, along with the del B drift, drive the asymmetries in parallel flows. A semian-alytical model based on mass and parallel momentum balances allows the poloidal drift effects on the asymmetry pattern to be evaluated. As in the experiments, a reversed B-T simulation provides a way of self-consistently separating the effects of turbulent transport and large-scale flows, which must be reversed for a reversed field. The large-scale contribution is found to be responsible for typically 50% of the effect on the Mach number, evaluated at the top of the machine. The presented picture shows the complex interplay between drifts and turbulence, underlining the necessity of a global approach to edge plasma modelling, including a self-consistent description of the turbulence.
Davide Galassi, P. Tamain, H. Bufferand, Guido Ciraolo, Ph. Ghendrih, et al.. Drive of parallel flows by turbulence and large-scale E × B transverse transport in divertor geometry. Nuclear Fusion, 2017, 57 (3), pp.036029. ⟨10.1088/1741-4326/aa5332⟩. ⟨hal-01592945⟩
Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Yannick Marandet, J. Bucalossi, et al.. Interchange Turbulence Model for the Edge Plasma in SOLEDGE2D-EIRENE. Contributions to Plasma Physics, 2016, 56 (6-8), pp.555-562. ⟨10.1002/ctpp.201610033⟩. ⟨hal-01455239⟩ Plus de détails...
Cross-field transport in edge tokamak plasmas is known to be dominated by turbulent transport. A dedicated effort has been made to simulate this turbulent transport from first principle models but the numerical cost to run these simulations on the ITER scale remains prohibitive. Edge plasma transport study relies mostly nowadays on so-called transport codes where the turbulent transport is taken into account using effective ad-hoc diffusion coeffecients. In this contribution, we propose to introduce a transport equation for the turbulence intensity in SOLEDGE2D-EIRENE to describe the interchange turbulence properties. Going beyond the empirical diffusive model, this system automatically generates profiles for the turbulent transport and hence reduces the number of degrees of freedom for edge plasma transport codes. We draw inspiration from the k-epsilon model widely used in the neutral fluid community. ((c) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Hugo Bufferand, Guido Ciraolo, Philippe Ghendrih, Yannick Marandet, J. Bucalossi, et al.. Interchange Turbulence Model for the Edge Plasma in SOLEDGE2D-EIRENE. Contributions to Plasma Physics, 2016, 56 (6-8), pp.555-562. ⟨10.1002/ctpp.201610033⟩. ⟨hal-01455239⟩
R. Futtersack, C. Colin, Patrick Tamain, Guido Ciraolo, Philippe Ghendrih, et al.. First Principle Modelling of Interplay between Langmuir Probes and Plasma Turbulence. Contributions to Plasma Physics, 2016, 56 (6-8), pp.575-580. ⟨10.1002/ctpp.201610038⟩. ⟨hal-01455240⟩ Plus de détails...
The interplay between Langmuir probes (LP) and Scrape-Off-Layer plasma turbulence is numerically investigated with the TOKAM2D and TOKAM3X fluid codes. The LP is modelled by biasing a part of the target plates surface; we then study its impact on the turbulent transport 1) in presence of electron temperature fluctuations and 2) with a complete description of the parallel dynamics. We find that a biased probe can disturb local plasma parameters as well as turbulent transport in its vicinity, by polarizing the connected flux tube and thus driving a strong ExB vortex. Moreover, electron temperature fluctuations are found to account significantly those of floating potential, but with a limited impact on flux measurements depending on the probe's exact geometry. The 3D study of the problem shows the attenuation, but the persistency, of these perturbations induced by the presence of the LP. ((c) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
R. Futtersack, C. Colin, Patrick Tamain, Guido Ciraolo, Philippe Ghendrih, et al.. First Principle Modelling of Interplay between Langmuir Probes and Plasma Turbulence. Contributions to Plasma Physics, 2016, 56 (6-8), pp.575-580. ⟨10.1002/ctpp.201610038⟩. ⟨hal-01455240⟩
Patrick Tamain, Hugo Bufferand, L. Carbajal, Yannick Marandet, C. Baudoin, et al.. Interplay between Plasma Turbulence and Particle Injection in 3D Global Simulations. Contributions to Plasma Physics, 2016, 56 (6-8), pp.569-574. ⟨10.1002/ctpp.201610063⟩. ⟨hal-01455242⟩ Plus de détails...
The impact of a 3D localized particle source on the edge plasma in 3D global turbulence simulations is investigated using the TOKAM3X fluid code. Results apply to advanced fueling methods such as Supersonic Molecular Beam Injection (SMBI) or pellets injection. The fueling source is imposed as a volumetric particle source in the simulations so that the physics leading to the ionization of particles and its localization are not taken into account. As already observed in experiments, the localized particle source strongly perturbs both turbulence and the large scale organization of the edge plasma. The localized increase of the pressure generated by the source drives sonic parallel flows in the plasma, leading to a poloidal redistribution of the particles on the time scale of the source duration. However, the particle deposition also drives localized transverse pressure gradients which impacts the stability of the plasma with respect to interchange processes. The resulting radial transport occurs on a sufficiently fast time scale to compete with the parallel redistribution of particles, leading to immediate radial losses of a significant proportion of the injected particles. Low Field Side (LFS) and High Field Side (HFS) injections exhibit different dynamics due to their interaction with curvature. In particular, HFS particle deposition drives an inward flux leading to differences in the particle deposition efficiency (higher for HFS than LFS). These results demonstrate the importance of taking into account plasma transport in a self-consistent manner when investigating fueling methods. ((c) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Patrick Tamain, Hugo Bufferand, L. Carbajal, Yannick Marandet, C. Baudoin, et al.. Interplay between Plasma Turbulence and Particle Injection in 3D Global Simulations. Contributions to Plasma Physics, 2016, 56 (6-8), pp.569-574. ⟨10.1002/ctpp.201610063⟩. ⟨hal-01455242⟩
Fabio Riva, Clothilde Colin, Julien Denis, Luke Easy, Ivo Furno, et al.. Blob dynamics in the TORPEX experiment: a multi-code validation. Plasma Physics and Controlled Fusion, 2016, 58 (4), ⟨10.1088/0741-3335/58/4/044005⟩. ⟨hal-01461784⟩ Plus de détails...
Three-dimensional and two-dimensional seeded blob simulations are performed with five different fluid models, all based on the drift-reduced Braginskii equations, and the numerical results are compared among themselves and validated against experimental measurements provided by the TORPEX device ( Fasoli et al 2006 Phys. Plasmas 13 055902). The five models are implemented in four simulation codes, typically used to simulate the plasma dynamics in the tokamak scrape-off layer, namely BOUT++ (Dudson et al 2009 Comput. Phys. Commun. 180 1467), GBS (Ricci et al 2012 Plasma Phys. Control. Fusion 54 124047), HESEL (Nielsen et al 2015 Phys. Lett. A 379 3097), and TOKAM3X (Tamain et al 2014 Contrib. Plasma Phys. 54 555). Three blobs with different velocities and different stability properties are simulated. The differences observed among the simulation results and the different levels of agreement with experimental measurements are investigated, increasing our confidence in our simulation tools and shedding light on the blob dynamics. The comparisons demonstrate that the radial blob dynamics observed in the three-dimensional simulations is in good agreement with experimental measurements and that, in the present experimental scenario, the two-dimensional model derived under the assumption of k(vertical bar vertical bar) = 0 is able to recover the blob dynamics observed in the three-dimensional simulations. Moreover, it is found that an accurate measurement of the blob temperature is important to perform reliable seeded blob simulations.
Fabio Riva, Clothilde Colin, Julien Denis, Luke Easy, Ivo Furno, et al.. Blob dynamics in the TORPEX experiment: a multi-code validation. Plasma Physics and Controlled Fusion, 2016, 58 (4), ⟨10.1088/0741-3335/58/4/044005⟩. ⟨hal-01461784⟩
Patrick Tamain, Philippe Ghendrih, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, et al.. Multi-scale self-organisation of edge plasma turbulent transport in 3D global simulations. Plasma Physics and Controlled Fusion, 2015, 57 (5), pp.054014. ⟨10.1088/0741-3335/57/5/054014⟩. ⟨hal-01299732⟩ Plus de détails...
The 3D global edge turbulence code TOKAM3X is used to study the properties of edge particle turbulent transport in circular limited plasmas, including both closed and open flux surfaces. Turbulence is driven by an incoming particle flux from the core plasma and no scale separation between the equilibrium and the fluctuations is assumed. Simulations show the existence of a complex self-organization of turbulence transport coupling scales ranging from a few Larmor radii up to the machine scale. Particle transport is largely dominated by small scale turbulence with fluctuations forming quasi field-aligned filaments. Radial particle transport is intermittent and associated with the propagation of coherent structures on long distances via avalanches. Long range correlations are also found in the poloidal and toroidal direction. The statistical properties of fluctuations vary with the radial and poloidal directions, with larger fluctuation levels and intermittency found in the outboard scrape-off layer (SOL). Radial turbulent transport is strongly ballooned, with 90% of the flux at the separatrix flowing through the low-field side. One of the main consequences is the existence of quasi-sonic asymmetric parallel flows driving a net rotation of the plasma. Simulations also show the spontaneous onset of an intermittent E × B rotation characterized by a larger shear at the separatrix. Strong correlation is found between the turbulent particle flux and the E × B flow shear in a phenomenology reminiscent of H-mode physics. The poloidal position of the limiter is a key player in the observed dynamics.
Patrick Tamain, Philippe Ghendrih, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, et al.. Multi-scale self-organisation of edge plasma turbulent transport in 3D global simulations. Plasma Physics and Controlled Fusion, 2015, 57 (5), pp.054014. ⟨10.1088/0741-3335/57/5/054014⟩. ⟨hal-01299732⟩
Clothilde Colin, Patrick Tamain, Frederic Schwander, Eric Serre, Hugo Bufferand, et al.. Impact of the plasma-wall contact position on edge turbulent transport and poloidal asymmetries in 3D global turbulence simulations. Journal of Nuclear Materials, 2015, 463, pp.654-658. ⟨10.1016/j.jnucmat.2015.01.019⟩. ⟨hal-01225200⟩ Plus de détails...
A 3D global turbulence fluid code, TOKAM3X is used to investigate the effect of the limiter position on the edge plasma parallel flows and density profiles. Six configurations with different poloidal contact points in the machine are considered. For each one, asymmetric quasi-sonic parallel flows are found, owing to the ballooning of radial turbulent transport around the LFS mid-plane. In spite of the relative simplicity of the model used (isothermal, sheat-limited, no recycling), simulations exhibit trends in-line with experimental findings. Reversal of the flows is found when the limiter is moved from −30° under to 30° above the outboard mid-plane. The SOL width varies with the poloidal location and depends notably on the poloidal position of the limiter. Turbulence itself is shown to be impacted by the position of the limiter, radial transport appearing less ballooned with a LFS limiter than with a HFS.
Clothilde Colin, Patrick Tamain, Frederic Schwander, Eric Serre, Hugo Bufferand, et al.. Impact of the plasma-wall contact position on edge turbulent transport and poloidal asymmetries in 3D global turbulence simulations. Journal of Nuclear Materials, 2015, 463, pp.654-658. ⟨10.1016/j.jnucmat.2015.01.019⟩. ⟨hal-01225200⟩
Patrick Tamain, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, Philippe Ghendrih, et al.. 3D properties of edge turbulent transport in full-torus simulations and their impact on poloidal asymmetries. Contributions to Plasma Physics, 2014, 54 (4-6), pp.555-559. ⟨10.1002/ctpp.201410017⟩. ⟨hal-01053290⟩ Plus de détails...
The 3D fluid turbulence code TOKAM3X is used to investigate the 3D properties of edge turbulent transport and their impact on poloidal asymmetries. Simulations are run in circular limited plasmas in a domain covering both closed and open flux surfaces. Turbulence characteristics exhibit large inhomogeneities both in the radial and poloidal directions reminiscent of experimental observations. The low field side mid-plane in particular is found to be locally more fluctuating and intermittent than the rest of the Scrape-Off-Layer (SOL). As a consequence of this asymmetry, radial turbulent transport, that represents 80 to 90% of the total radial flux, is strongly ballooned, with 75% of the flux flowing through LFS. The equilibrium of the edge plasma is impacted by this asymmetry through the existence of large amplitude asymmetric parallel flows as well as through the development of poloidally asymmetric radial decay lengths making it impossible to define a single SOL width.
Patrick Tamain, Hugo Bufferand, Guido Ciraolo, Clothilde Colin, Philippe Ghendrih, et al.. 3D properties of edge turbulent transport in full-torus simulations and their impact on poloidal asymmetries. Contributions to Plasma Physics, 2014, 54 (4-6), pp.555-559. ⟨10.1002/ctpp.201410017⟩. ⟨hal-01053290⟩
Clothilde Colin, Patrick Tamain, Philippe Ghendrih, Frederic Schwander, Eric Serre. Impact of a Langmuir probe on turbulence measurements in the Scrape-Off-Layer of tokamaks. Contributions to Plasma Physics, 2014, 54 (4-6), pp.543-548. ⟨10.1002/ctpp.201410087⟩. ⟨hal-01019696⟩ Plus de détails...
An issue for Langmuir probe measurements of SOL turbulence concerns the impact of the probe itself on plasma transport. The aim of this paper is to investigate this issue with a synthetic reconstruction of Langmuir probe measurements by inserting a synthetic probe into a 2D fluid SOL turbulence code. The effect of a biased probe is analysed as a function of its size. It is shown that the probe creates a transport barrier whose effect is non-local and affects the current's circulation in the plasma. The plasma density is depleted by the presence of the probe as well as the electrostatic potential. A strong impact on turbulence can also be observed. Such observations imply that the probed turbulence can differ significantly from the probe-free turbulence
Clothilde Colin, Patrick Tamain, Philippe Ghendrih, Frederic Schwander, Eric Serre. Impact of a Langmuir probe on turbulence measurements in the Scrape-Off-Layer of tokamaks. Contributions to Plasma Physics, 2014, 54 (4-6), pp.543-548. ⟨10.1002/ctpp.201410087⟩. ⟨hal-01019696⟩
