A5046920162- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Fluid Dynamics and Turbulent Flows
- Meteorological Phenomena and Simulations
- Atomic and Subatomic Physics Research
- Blind Source Separation Techniques
- earthquake and tectonic studies
- Theoretical and Computational Physics
- Magneto-Optical Properties and Applications
- Laser-induced spectroscopy and plasma
- GNSS positioning and interference
- Wind and Air Flow Studies
- Seismic Imaging and Inversion Techniques
- Quantum chaos and dynamical systems
- Geomagnetism and Paleomagnetism Studies
- Atomic and Molecular Physics
- Dust and Plasma Wave Phenomena
- Astro and Planetary Science
- Gyrotron and Vacuum Electronics Research
CEA Cadarache
2015-2024
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2015-2024
Institut de Recherche sur la Fusion par Confinement Magnétique
2010-2024
Culham Science Centre
2018-2019
Ghent University
2018-2019
Aix-Marseille Université
2009-2012
Centre National de la Recherche Scientifique
1998-2009
École Polytechnique
1998-2008
Université de Lorraine
2006
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...
With WEST (Tungsten Environment in Steady State Tokamak) (Bucalossi et al 2014 Fusion Eng. Des. 89 907–12), the Tore Supra facility and team expertise (Dumont Plasma Phys. Control. 56 075020) is used to pave way towards ITER divertor procurement operation. It consists implementing a configuration installing ITER-like actively cooled tungsten monoblocks tokamak, taking full benefit of its unique long-pulse capability. user platform, open all partners. This paper describes physics basis WEST:...
Anomalous transport in tokamaks is generally attributed to turbulent fluctuations. Since a large variety of modes are potentially unstable, wide range short-scale fluctuations should be measured, with wavenumbers from kρi ∼ 0.1 ≫ 1. In the Tore Supra tokamak, light scattering experiment has made possible fluctuation measurements medium- and high-k domains where transition k-spectrum observed: level decreases much faster than usual observations, typically power law S(k) ≡ k−6. A scan ion...
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...
This letter reports on quasi-coherent (QC) modes observed in fluctuation spectra from Tore Supra and TEXTOR reflectometers. QC have characteristics between coherent broad-band fluctuations as they oscillate around a given frequency but wide spectrum. They are ballooned at the LFS midplane appear usually ranging 30 to 120 kHz. In ohmic plasmas both tokamaks, detected only linear confinement (LOC) regime disappear saturated (SOC) regime. Linear simulations predict that LOC SOC regimes...
Backscattering of a microwave beam launched in oblique incidence makes possible measurement density fluctuations close to the cut-off with selected wave number k⃗⊥=−2k⃗i, where k⃗i is vector at reflection layer. On system installed on Tore Supra, Gaussian controlled thanks tiltable monostatic antenna. The part based fluctuation reflectometer scheme heterodyne detection, and choice V band (50–75 GHz) source O mode polarization appropriate for typical enhanced plasma regimes (n0=3–7×1019 m−3)....
Reflectometry with wavelengths in the centimetre to millimetre-wave range will be used ITER measure density profile main plasma and divertor regions position shape order provide a reference for magnetic diagnostics long pulses. In addition, it is expected key information measurement of fluctuations. A set reflectometers meet relevant requirements has been included its present outline as part design since 2001 being adapted baseline accommodate progress reflectometry techniques capabilities....
The influence of changing collisionality on density fluctuation characteristics is studied during dedicated ν∗ scaling experiments, using Doppler backscattering system. First, the repartition energy over different spatial scales, as represented by wavenumber spectrum, investigated and a modification shape perpendicular spectrum in low part observed when collisionality. In addition, new procedure to evaluate dispersion relation micro-turbulence presented. From behavior mean velocity...
Ion temperature gradient (ITG) and trapped electron modes (TEM) are two important micro-instabilities in the plasma core region of fusion devices (). They usually coexist same range spatial scale (around ), which makes their discrimination difficult. To investigate them, one can perform gyrokinetic simulations, transport analysis phase velocity estimations. In Tore Supra, identification is made possible due to measured frequency fluctuation spectra. Indeed, turbulent spectra generally...
Quasi-coherent (QC) modes have been reported for more than 10 years in reflectometry fluctuations spectra the core region of fusion plasmas. They characteristics in-between coherent and broadband as they oscillate at a marked frequency but wide spectrum. This work presents further evidences link recently established between QC trapped electron (TEM) instabilities (Arnichand et al 2014 Nucl. Fusion 54 123017). In cyclotron resonance heated discharges Tore Supra, an enhancement amplitude is...
Abstract In-depth experimental characterisation of spontaneous shear flow patterning into a so-called <?CDATA $\mathbf{E}\times \mathbf{B}$ ?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mstyle displaystyle="false"> <mml:mrow> <mml:mi mathvariant="bold">E</mml:mi> </mml:mrow> <mml:mo>×</mml:mo> mathvariant="bold">B</mml:mi> </mml:mstyle> </mml:math> staircase—named after its planetary analogue—is shown in magnetised plasma turbulence, using...
JET’s frequency-modulated continuous wave (FMCW) reflectometers have been operating well with the current design since 2005, and density profiles automatically calculated intershot then. However, had long suffered from several shortcomings: poor agreement other diagnostics, sometimes inappropriately moving radially by centimeters, elevated levels of radial jitter, persistent wriggles (strong unphysical oscillations). In this research, techniques are applied to reflectometry data analysis,...
Significant improvements have been achieved in the performances of broadband reflectometry for density profile measurements on Tore Supra. The frequency range former 50–75 GHz X-mode reflectometer has extended with an additional device operating between 75 and 110 GHz. Both setups ultrafast sweeping capabilities allowing full band 20 μs. heterodyne detection intermediate system upgraded to record beat frequencies up 100 MHz a signal noise ratio about 40 dB. phase quadrature-type (IQ...
This paper describes what we can learn on the regimes of spontaneous electron temperature oscillations discovered in Tore Supra from analysis MHD activity. Since first observations this oscillating behaviour plasma equilibrium, and its interpretation as a predator–prey system involving lower hybrid waves power deposition confinement, modes has confirmed reality safety factor profile oscillations. points towards importance rational values transition to transport barriers reversed magnetic...
Over the last years, owing to hardware progress and development of new methods, reflectometry has become a common diagnostic on plasma fusion devices. This paper presents some results obtained with transport, turbulence magnetohydrodynamic (MHD). The emphasis is put from Tore-Supra. Combining density profile fluctuation measurement, it was shown Tore-Supra that particle pinch inside q = 1 surface close neoclassical value in ohmic plasma, while observed small diffusion agreement very low...
The turbulent impurity (nickel) transport dependence on the normalized electron temperature gradient has been analyzed in sawtooth-free cyclotron wave heated Tore Supra plasmas. In core, our experimental analysis shows that lower $R/{L}_{{T}_{e}}$, nickel diffusion coefficient. latter decreases until instability threshold is reached. agreement with one computed by a gyrokinetic model. Further out, $R/{L}_{{T}_{e}}$ plays no role diffusion. This set of results consistent quasilinear analysis.
Modes oscillating at the acoustic frequency and identified as beta Alfvén eigenmodes (BAEs) have been observed in Tore-Supra under ion cyclotron resonant heating. In this paper, linear excitation threshold of these modes, thought to be driven by suprathermal ions, is calculated compared with observations. Similar studies energetic particles modes were carried out previously for toroidal or fishbones. case BAEs, main point understand whether particle drive able exceed Landau damping, which...
The transport of impurities by a sawtooth crash is simulated with the XTOR-2F code. Impurities are modeled as passive scalars, evolving in compressible MHD flow inferred from main plasma. For peaked impurity density profile, non-linear kink redistributes profile efficiently and most particles peak inside q = 1 surface expelled. an initially hollow leads to significant penetration up magnetic axis. results compared Kadomtsev's model. Despite essentially different mechanisms, evolution...
Tungsten transport is investigated in WEST long pulse L-mode plasmas operated with the strike point on actively cooled upper tungsten divertor. The pulses are mostly heated by lower hybrid waves. It experimentally found that does not centrally accumulate throughout these ∼ 30 s reproducible discharges despite large normalised electron density gradients . To explain observations, turbulent and neoclassical of electrons ions computed GKW Peeters A.G. et al (2009 Computer Phys. Commnun. 180...
A broadband reflectometer operating in the frequency range 50-75 GHz has been developed on Tore Supra to measure electron density profiles at edge. The system uses extraordinary mode polarization and performs routine measurements 20 µs with heterodyne detection ensure a high dynamic sensitivity. It allows separate phase amplitude information of signal. are fully automatically calculated from raw phase. initialization is done automatic first cut-off reflected signal an accuracy up ±0.5 cm....
The stepped fixed frequency X-mode reflectometer operating between 105 and 155 GHz first designed for density fluctuation measurement has been upgraded to also measure the profile. It runs now with two sources in parallel: a fast swept source synthesizer during same shot profile fluctuations. accuracy of from reflectometry reduces uncertainties on measurement. This double mode offers ways probe MHD modes micro-turbulence.
MHD instabilities driven by fast electrons identified as fishbonelike modes have been detected on Tore Supra during lower hybrid current drive discharges. Direct experimental evidence is reported of a novel feature: the regular redistribution suprathermal toward external tokamak regions which are correlated to periodic mode frequency jumps. Sharp drops electron temperature time trace factually linked cyclical deterioration confinement.