A5064285977- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Fusion materials and technologies
- Fluid Dynamics and Turbulent Flows
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Quantum chaos and dynamical systems
- Theoretical and Computational Physics
- Geomagnetism and Paleomagnetism Studies
- Physics of Superconductivity and Magnetism
- Laser-induced spectroscopy and plasma
- High-pressure geophysics and materials
- Nuclear reactor physics and engineering
- Meteorological Phenomena and Simulations
- Electromagnetic Launch and Propulsion Technology
- earthquake and tectonic studies
- Atomic and Subatomic Physics Research
- Oceanographic and Atmospheric Processes
- Quantum, superfluid, helium dynamics
- Granular flow and fluidized beds
- Aerosol Filtration and Electrostatic Precipitation
- Cold Fusion and Nuclear Reactions
CEA Cadarache
2016-2025
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2016-2025
Institut de Recherche sur la Fusion par Confinement Magnétique
2014-2025
CEA Grenoble
2021
Canadian Nautical Research Society
2021
Hôpital Xavier Arnozan
2021
Dutch Institute for Fundamental Energy Research
2018
Culham Science Centre
2018
General Atomics (United States)
2018
Japan External Trade Organization
2015
Interchange turbulence in two dimensions is investigated the scrape-off layer (SOL) of fusion devices, when driven by a constant core particle influx. Contrary to standard gradient-driven approach, density allowed fluctuate around its average profile. Transverse transport exhibits some features self-organized critical systems, namely inward and outward avalanches, together with frequency spectrum decrease 1/f f−2 at intermediate high frequencies, respectively. An avalanche occurs local...
A systematic, constructive and self-consistent procedure to quantify nonlocal, nondiffusive action at a distance in plasma turbulence is exposed applied turbulent heat fluxes computed from the state-of-the-art full-$f$, flux-driven gyrokinetic GYSELA XGC1 codes. striking commonality found: transport below dynamically selected mesoscale has structure of L\'evy distribution, strongly nondiffusive, scale-free, avalanche mediated; larger scales, we report observation self-organized flow which...
An overview of the physics intrinsic torque is presented, with special emphasis on phenomenology toroidal rotation in tokamaks, its theoretical understanding, and variety momentum transport bifurcation dynamics.Ohmic reversals ECH-driven counter are discussed some detail.Symmetry breaking by LSN vs. USN asymmetry related to origin at separatrix.
Turbulence in hot magnetized plasmas is shown to generate permeable localized transport barriers that globally organize into the so-called "ExB staircase" [G. Dif-Pradalier et al., Phys. Rev. E, 82, 025401(R) (2010)]. Its domain of existence and dependence with key plasma parameters discussed theoretically. Based on these predictions, staircases are observed experimentally Tore Supra tokamak by means high-resolution fast-sweeping X-mode reflectometry. This observation strongly emphasizes...
The turbulent transport governed by the toroidal ion temperature gradient driven instability is analysed with full- f global gyrokinetic code GYSELA (Grandgirard et al 2007 Plasma Phys. Control. Fusion 49 B173 ) when system a prescribed heat source. Weak, yet finite, collisionality governs neoclassical flux that can compete transport. In turn, ratio of to increases source magnitude, resulting in degradation confinement additional power. exhibits avalanche-like events, characterized...
The impact on turbulent transport of geodesic acoustic modes excited by energetic particles is evidenced for the first time in flux-driven 5D gyrokinetic simulations using Gysela code. Energetic (EGAMs) are a regime with barrier outer radial region. interaction between EGAMs and turbulence such that can be enhanced presence EGAMs, subsequent destruction barrier. This scenario could particularly critical those plasmas, as burning exhibiting rich population suprathermal capable exciting modes.
We show that a class of near-marginal and low-collisional magnetised plasmas naturally evolve into globally organised state dubbed the ' × E B staircase'.A key signature this self-organised is containment avalanche activity, detrimental for confinement, by series microbarriers transport, staircase steps, beneficial confinement.Conditions existence staircase, impact on transport confinement robustness in parameter space are discussed.
The effect of a sheared toroidal velocity on transport barrier is studied. This analysis done by using three-dimensional global fluid simulations electrostatic ion temperature gradient driven turbulence in tokamaks. produced with reversed magnetic shear. For flat density profile, and at low collisionality, co-rotation leads to an outward motion the barrier, whereas counter rotation inward displacement. However, displacement saturates when increasing torque fixed heat source. saturation...
Critical physical issues can be specifically tackled with the global full-f gyrokinetic code GYSELA. Three main results are presented. First, self-consistent treatment of equilibrium and fluctuations highlights competition between two compensation mechanisms for curvature driven vertical charge separation, namely, parallel flow polarization. The impact latter on turbulent transport is discussed. In non-linear regime, benchmark Particle-In-Cell ORB5 looks satisfactory. Second, scaling ρ*...
In order to gain reliable predictions on turbulent fluxes in tokamak plasmas, physics based transport models are required. Nonlinear gyrokinetic electromagnetic simulations for all species still too costly terms of computing time. On the other hand, interestingly, quasi-linear approximation seems retain relevant fairly reproducing both experimental results and nonlinear simulations. Quasi-linear made two parts: (1) response transported quantities (2) saturated fluctuating electrostatic...
Turbulence measurements in TORE SUPRA tokamak plasmas have been quantitatively compared to predictions by nonlinear gyrokinetic simulations. For the first time, numerical results simultaneously match within experimental uncertainty (a) magnitude of effective heat diffusivity, (b) rms values density fluctuations, and (c) wave-number spectra both directions perpendicular magnetic field. Moreover, simulations help revise as an instrumental effect apparent evidence strong turbulence anisotropy...
Flux-driven global gyrokinetic codes are now mature enough to make predictions in terms of turbulence and transport tokamak plasmas. Some the recent breakthroughs three such codes, namely GYSELA, ORB5 XGC1, reported compared wherever appropriate. In all turbulent appears be mediated by avalanche-like events, for a broad range ρ * = i / values, ratio gyro-radius over minor radius. Still, radial correlation length scales with , leading gyro-Bohm scaling effective coefficient below ≈ 1/300. The...
We show in this paper that geodesic acoustic modes (GAMs) can be efficiently excited by a population of fast ions even when Landau damping on thermal is accounted for. report particular fully kinetic calculations the GAM dispersion relation and its complete solution. Written under variational form, quasi-neutrality condition, together with Vlasov equation, leads to density exchanged energy between particles mode. In particular, linear threshold for GAMs excitation derived. Two examples ion...
Recent progress in experimental and theoretical studies of edge localized mode (ELM) physics is reviewed for the reactor relevant plasma regimes, namely high confinement that is, H-modes advanced scenarios.
The entropy production rate is calculated for an interchange driven turbulence both in fluid and kinetic regimes. This calculation provides a rigorous way to define thermodynamical forces fluxes. It found that the are gradients of density temperature normalized their “canonical” values, which Lagrangian invariants flow. formulation equivalent expressing fluxes terms “curvature pinches,” where curvature pinches proportional logarithmic gradient canonical profiles. Off diagonal transport...
This paper analyzes the properties of a two-field critical gradient model that couples heat equation to an evolution for turbulence intensity. It is shown dynamics perturbation ballistic or diffusive depending on shape pulse and also distance temperature instability threshold. dual character appears in linear response this wave packet. recovered when investigating nonlinear solutions system. Both self-similar fronts are exist. When propagation ballistic, it found front velocity geometric...
The impact of ion-ion collisions on confinement is investigated with the full-$f$ and global gyrokinetic Gysela code through a series nonlinear turbulence simulations for tokamak parameters. A twofold scan in drive collisionality performed, highlighting (i) heat transport expressed terms critical quantities---threshold exponent, (ii) first evidence turbulent generation poloidal momentum, (iii) dominance mean flow shear, mediated corrugation profiles, regard to oft-invoked zonal shear.
Conservation equations are derived for the gyrocenter toroidal momentum density and polarization field. These from gyrokinetic model as it is implemented in simulation codes. In view of predicting rotation future fusion devices such ITER, where external input will be small, accurate simulations transport crucial. The evolution equation involves divergence off-diagonal components Reynolds generalized Maxwell stress, while source term radial current gyrocenters. time field opposite current....
In this paper, the nature of primary instability present in pedestal forming region prior to transition into H mode is analysed using a gyrokinetic code on JET-ILW profiles. The linear analysis shows that resistive nature, and can therefore be stabilized by increased temperature, hence power. unstable modes are identified as being ballooning modes. Their growth rates decrease for temperatures increasing towards experimentally measured temperature at L–H transition. larger lower effective...
Abstract Magnetic confinement fusion offers the promise of sustainable and safe energy production on Earth. Advanced experimental scenarios exploit fascinating yet uncommon ability confined plasmas to bifurcate into states enhanced performance upon application additional free sources. Self-regulation small-scale turbulent eddies is essential accessing these improved regimes. However, after several decades, basic principles for bifurcations are still largely debated clarifications from first...
Abstract The effects of transport barriers on impurity transport, specifically helium (He) and tungsten (W), are investigated using the global, flux-driven, full-F, 5D gyrokinetic code GYSELA. barrier is induced by triggering E×B shear via an external poloidal momentum source, thereby stabilizing ITG turbulence reducing outward heat fluxes. These reductions in particle fluxes due to lead enhanced confinement, steepening ion temperature profiles diffusivity main species (i.e. deuterium)....
Two-dimensional fluid simulations of scrape-off layer (SOL) turbulence with non-constrained energy content (flux driven) are characterized by profile relaxation and strong outward bursts density. The ballistic propagation extends well beyond the e-folding length SOL a Mach number M⊥ ∼ 0.04. Turbulence stabilization is achieved biasing part limiter surface. critical radial extent to achieve this derived. This effect governs size biased ring required insulate wall from long range matter. same...