Amplification de rayonnement XUV dans les plasmas crees par laser : etude d'un schema combine d'excitation optique et collisionnelle dans les ions isoelectroniques du neon

CNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Collisional-Radiative modeling of the transient excitation of a carbon atoms beam crossing a tokamak plasma edge

WOS:000337223400045International audienceA time-dependent collisional-radiative (CR) model is elaborated in the purpose of modeling the penetration of an atomic carbon beam in the edge plasma of a fusion machine in order to probe it. The excited states population densities of the beam are assumed to be modified by electron-induced processes only. All momentum transfer is neglected: the penetration velocity is assumed constant. In typical conditions for the electron density and temperature gradients (partial derivative n(e)/partial derivative(x) approximate to 10(20) m(-4) and partial derivative T-e/partial derivative(x) approximate to 10(7) K m(-1)), the results illustrate the electrons efficiency to ionize the beam. With a velocity equal to 1 km s(-1), the beam is ionized in 20 mu s in these conditions, which corresponds to a penetration depth of 2 cm. During the conversion in ions, the atomic beam is sufficiently excited to emits spectra whose measurement in coupling with the present CR model can provide information on partial derivative n(e)/partial derivative(x) and partial derivative T-e/partial derivative(x)

Collisional-Radiative modeling of the transient excitation of a carbon atoms beam crossing a tokamak plasma edge

WOS:000337223400045International audienceA time-dependent collisional-radiative (CR) model is elaborated in the purpose of modeling the penetration of an atomic carbon beam in the edge plasma of a fusion machine in order to probe it. The excited states population densities of the beam are assumed to be modified by electron-induced processes only. All momentum transfer is neglected: the penetration velocity is assumed constant. In typical conditions for the electron density and temperature gradients (partial derivative n(e)/partial derivative(x) approximate to 10(20) m(-4) and partial derivative T-e/partial derivative(x) approximate to 10(7) K m(-1)), the results illustrate the electrons efficiency to ionize the beam. With a velocity equal to 1 km s(-1), the beam is ionized in 20 mu s in these conditions, which corresponds to a penetration depth of 2 cm. During the conversion in ions, the atomic beam is sufficiently excited to emits spectra whose measurement in coupling with the present CR model can provide information on partial derivative n(e)/partial derivative(x) and partial derivative T-e/partial derivative(x)

Flow generation and intermittent transport in the scrape-off-layer of the Tore Supra tokamak

International audienceResults on transport in the scrape-off-layer from a set of ohmic discharges in Tore Supra are discussed. The particle balance in the SOL is described trough a steady-state model that utilizes profile measurements from reciprocating-probes. Experimental evidence of the non-uniformity in the poloïdal distribution of particle outflux is found, with the highest outflux being concentrated in a narrow sector at the outboard midplane. High and intermittent fluctuations originating from the same outboard midplane sector are interpreted as the signature of the transport mechanisms that result in the time-averaged equilibrium. The radial convection of subsonic structures is assumed as the dominant transport process

Experimental investigation on the poloidal extent of the turbulent radial flux in tokamak scrape-off layer

Proceedings of the 19th International Conference on Plasma-Surface Interactions in Controlled FusionInternational audienceA consistent description of scrape-off layer transport is built from multi-diagnostic observations in ohmic discharges in Tore Supra. Fast imaging reveals the existence of relatively large filamentary structures on the low field side but not on the high field side of the torus. These filaments can exist either on open or closed magnetic flux surfaces and have a finite parallel extent from the outboard midplane. Probe electrostatic turbulence measured at the top of the plasma corresponds to the ExB convection of density burst, understood as the signature of filament propagation. Independent experiments on time-averaged parallel flows measured with a Mach probe lead to a poloidal mapping of the strongly asymmetric radial flux. This flux is centered at the outboard midplane and its poloidal half width is about 50°. The local turbulent flux on the top is consistent with the mapping

Tomographic reconstruction of tokamak plasma light emission from single image using wavelet-vaguelette decomposition

International audienceImages acquired by cameras installed in tokamaks are difficult to interpret because the three-dimensional structure of the plasma is flattened in a non-trivial way. Nevertheless, taking advantage of the slow variation of the fluctuations along magnetic field lines, the optical transformation may be approximated by a generalized Abel transform, for which we propose an inversion technique based on the wavelet-vaguelette decomposition. After validation of the new method using an academic test case and numerical data obtained with the Tokam 2D code, we present an application to an experimental movie obtained in the tokamak Tore Supra. A comparison with a classical regularization technique for ill-posed inverse problems, the singular value decomposition, allows us to assess the efficiency. The superiority of the wavelet-vaguelette technique is reflected in preserving local features, such as blobs and fronts, in the denoised emissivity map

The effect of SOL flows on edge and core radial electric field and rotation in Tore Supra

International audienc

A first comparison between probes, fast imaging, and reflectometry synchronous measurements of edge turbulence in Tore Supra

International audienceOra