A5014371543- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Muon and positron interactions and applications
- Complex Systems and Time Series Analysis
- Theoretical and Computational Physics
- Nuclear reactor physics and engineering
- Atomic and Molecular Physics
- Fluid Dynamics and Turbulent Flows
- Atomic and Subatomic Physics Research
- Statistical Mechanics and Entropy
- High-pressure geophysics and materials
- Quasicrystal Structures and Properties
- Image and Signal Denoising Methods
- Meteorological Phenomena and Simulations
- Laser-induced spectroscopy and plasma
- COVID-19 Clinical Research Studies
- Long-Term Effects of COVID-19
- Nuclear Physics and Applications
- Geomagnetism and Paleomagnetism Studies
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
2014-2024
Universidad Complutense de Madrid
2013-2024
Complejo Hospitalario Torrecárdenas
2022-2024
Unidades Centrales Científico-Técnicas
1998-2021
Center of Molecular Immunology (Cuba)
2020
Royal Military Academy
2020
Victoria School of Management
2020
Culham Science Centre
2005-2018
Instituto Superior Técnico
2006-2016
Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento
2016
This paper reviews measurements of edge plasma turbulence in toroidal magnetic fusion devices with an emphasis on recent results tokamaks. The dominant feature is a high level broadband density fluctuations relative amplitude δn/n ∼ 5–100%, accompanied by large potential and electron temperature fluctuations. frequency range this ∼10 kHz–1 MHz, the size scale typically ∼0.1–10 cm perpendicular to field but many metres along field, i.e. structure nearly that 2D 'filaments'. Large intermittent...
A recently introduced tool for the analysis of turbulence, wavelet bicoherence [van Milligen, Hidalgo, and Sánchez, Phys. Rev. Lett. 16, 395 (1995)], is investigated. It capable detecting phase coupling—nonlinear interactions lowest (quadratic) order—with time resolution. To demonstrate its potential, it applied to numerical models chaos turbulence real measurements. detected coupling interaction between two coupled van der Pol oscillators. When a model drift wave relevant plasma physics,...
As the finalization of a hydrogen experiment towards deuterium phase, exploration best performance plasma was intensively performed in large helical device. High ion and electron temperatures, Ti Te, more than 6 keV were simultaneously achieved by superimposing high-power cyclotron resonance heating onneutral beam injection (NBI) heated plasma. Although flattening temperature profile core region observed during discharges, one could avoid degradation increasing density. Another key parameter...
Abstract Fusion energy research has in the past 40 years focused primarily on tokamak concept, but recent advances plasma theory and computational power have led to renewed interest stellarators. The largest most sophisticated stellarator world, Wendelstein 7-X (W7-X), just started operation, with aim show that earlier weaknesses of this concept been addressed successfully, intrinsic advantages persist, also at parameters approaching those a future fusion plant. Here we first physics...
In this paper, recent progress on experimental analysis and theoretical models for non-local transport (non-Fickian fluxes in real space) is reviewed. The non-locality the heat momentum observed plasma, departures from linear flux-gradient proportionality, externally triggered phenomena are described both L-mode improved-mode plasmas. Ongoing evaluation of 'fast front' 'intrinsically non-local' models, their success comparisons with data, discussed
Analysis of the edge plasma fluctuation in several confinement devices reveals self-similar character fluctuations through presence long-range time correlations. These results show that tail autocorrelation function decays as a power law for lags longer than decorrelation and long times on order particle diffusion time. The algebraic decay correlations is consistent with transport characterized by self-organized criticality.
A new technique combining wavelet analysis and bispectral has been developed. This tool permits the detection of structure in turbulent or chaotic data with time resolution, even presence a significant noise contribution. Application this to obtained fusion plasmas Langmuir probes demonstrates its possibilities by detecting short-lived intermittent nonlinear coupling. Its application field chaos is indicated.
The rescaled range analysis techniques are used to investigate long-range dependence in plasma edge fluctuations [Mandelbrot and Wallis, Water Resources Res. 4, 909 (1969)]. This technology has been applied data from several confinement devices such as tokamaks, stellarators, reversed-field pinch. results reveal the self-similar character of electrostatic at with self-similarity parameters ranging 0.62 0.72. These show that tail autocorrelation function decays a power law for time lags...
Fluctuation-induced fluxes have a bursty character. As consequence, significant part of the total particle flux is carried out by sporadic, large transport bursts. The local distribution function consistent with near-Gaussian character fluctuations. radial dependence statistical properties plasma fluctuations and induced been investigated in boundary region TJ-I tokamak [I. García-Cortés et al., Phys. Fluids B 4, 4007 (1992)] TJ-IU torsatron [E. Ascasibar Plasma Physics Controlled Fusion...
The present status of experiments on zonal flows in magnetic confinement is examined. innovative use traditional and modern diagnostics has revealed unambiguously the existence flows, their spatio-temporal characteristics, relationship to turbulence effects confinement. In particular, a number observations have been accumulated oscillatory branch named geodesic acoustic modes, suggesting necessity for theories give proper description. addition these basic properties several new methods...
Sheared flows have been experimentally studied in TJ-II plasmas. In low-density ECH plasmas, sheared can be easily controlled by changing the plasma density, thereby allowing radial origin and evolution of edge velocity shear layer to studied. high density NBI heated plasmas a negative electric field is observed that dominated diamagnetic component. The increases at L–H transition an amount depends on magnetic configuration heating power. Magnetic configurations with without low order...
The spatiotemporal behavior of the interaction between turbulence and flows has been studied close to L-H transition threshold conditions in edge region (ρ≥0.7) TJ-II plasmas. temporal dynamics displays an oscillatory with a characteristic predator-prey relationship. spatial evolution this turbulence-flow oscillation pattern measured, showing both radial outward inward propagation velocities front. results indicate that shear flow linked can behave either as slowing-down, damping mechanism...
The first experimental evidence showing the connection between blob/hole formation and zonal-flow generation was obtained in edge plasma of JET tokamak. Holes as well blobs are observed to be born shear layer, where zonal-flows off meso-scale coherent structures, leading disconnection positive negative pressure perturbations. newly formed transport azimuthal momentum up gradient flow drive while moving outwards. During this process energy is transferred from structures zonal flows via...
The dynamics of turbulence and plasma flows has been studied experimentally by means Doppler reflectometry during the transition from low to high confinement mode in stellarator TJ-II. Close threshold, gradual transitions are achieved showing an intermediate, oscillatory transient phase that facilitates study mechanisms involved transition. A coupling between sheared level is measured which reveals a characteristic predator-prey behavior consistent with L-H models based on turbulence-driven flows.
Advanced Langmuir probe techniques for evaluating the plasma potential and electron-energy distribution function (EEDF) in magnetized are reviewed. It is shown that when magnetic field applied very weak electrons reach without collisions sheath second-derivative Druyvesteyn formula can be used EEDF evaluation. At low values of field, an extended yields reliable results, while at higher first-derivative technique applicable precise evaluation EEDF. There interval intermediate both...
We show that the modulational instability growth rate of zonal flows is determined directly from quasilinear wave kinetic equation. also demonstrate relation between zonal-flow and cross bispectrum high-frequency drift-wave-driven Reynolds stress low-frequency plasma potential by explicit calculation. Experimental measurements spatiotemporal evolution spectrum integrated bicoherence at L-->H transition near edge shear layer indicate a modification in nonlinear phase coupling, which might be...
The probability distribution function of the turbulence-induced particle flux at plasma edge has distinct functional forms over two ranges time scales. One range corresponds to fluctuation scales and other one is mesoscale range: between turbulence decorrelation confinement time. In second range, self-similar essentially only outward tail. This structure reflects some mechanisms underlying turbulence.
The first experimental campaign of the TJ-II stellarator has been conducted using electron cyclotron resonance heating (, ) with a pulse length . flexibility device used to study five different configurations varying plasma volume and rotational transform. In this paper, main results are presented and, in particular, influence plasma-wall interaction phenomena on confinement is briefly discussed.
A view of the latest experimental results and progress in characterization understanding edge turbulence is given. The development new fluctuation analysis techniques has provided a bridge between measurements theoretical models. At same time, turbulent transport stimulated developments measurement electron temperature fluctuations; it been shown that substantial levels fluctuations are present boundary region magnetically confined plasmas. Several driving (curvature, atomic physics, . .)...
Long-distance coupling between edge parameters' fluctuations has been investigated in the TJ-II stellarator. Results show long-range correlations potential fluctuations, which are amplified by development of radial electric fields during transitions to improved-confinement regimes, whereas there is no correlation ion saturation current signals. These experimental findings suggest importance as a new fingerprint plasma behavior shear flows and key role amplify them.
This paper presents the latest results on confinement studies in TJ-II stellarator. The inherently strong plasma–wall interaction of has been successfully reduced after lithium coating by vacuum evaporation. Besides H retention and low Z , Li was chosen because there exists a reactor-oriented interest this element, thus giving special relevance to investigation its properties. Li-coating led important changes plasma performance. Particularly, effective density limit NBI plasmas extended...
Heavy ion beam probing (HIBP) is a unique diagnostics to study the core plasma potential and turbulence. Advanced HIBPs operate in T-10 tokamak TJ-II flexible heliac with fine focused (<1 cm) intense (100 µA) beams. They provide measurements wide density interval = (0.3–5) × 1019 m−3, range of Ohmic electron cyclotron resonance heated (ECRH) discharges various currents at T-10, magnetic configurations ECR neutral injection (NBI) heating TJ-II. Time evolution radial profiles and/or local...
The influence of the ion mass on dynamics magnetized plasmas is an important challenge in fusion research. discrepancies between improvement magnetic confinement with tokamak experiments and diffusive turbulent transport predictions have remained unexplained for several decades. We refer to this phenomenon as isotope effect. In paper, we study effect gyrokinetic theory using Gene code. find sets plasma parameters that correspond low wavenumber turbulence which present, although intensity...
Abstract The effect of magnetic islands on plasma flow and turbulence has been experimentally investigated in ohmically induced configuration scans at the stellarator TJ-II. This operational mode allows sweeping radial position a low order rational surface from core towards edge controlled way, what reveals effects that are difficult to notice performed shot basis. main diagnostic used present work is two-channel Doppler reflectometer measurement perpendicular rotation velocity density...