A5073657572- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Fusion materials and technologies
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Laser-induced spectroscopy and plasma
- Nonlinear Dynamics and Pattern Formation
- Atomic and Molecular Physics
- Laser-Matter Interactions and Applications
- Plasma Diagnostics and Applications
- Astro and Planetary Science
- Anomaly Detection Techniques and Applications
- Atomic and Subatomic Physics Research
- Advanced Fiber Laser Technologies
- Nuclear Physics and Applications
- Laser Design and Applications
- Chaos control and synchronization
- Medieval Architecture and Archaeology
- stochastic dynamics and bifurcation
- Image and Signal Denoising Methods
- Spectroscopy and Laser Applications
- Slime Mold and Myxomycetes Research
- Quantum optics and atomic interactions
Universidad Complutense de Madrid
2014-2024
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
1996-2024
Universidad de Deusto
2024
Universidad Carlos III de Madrid
2017
Universidad de Navarra
2013
Fusion for Energy
2002-2010
Fusion (United States)
2007
Fusion Academy
2007
Hospital Universitario La Paz
2003
Unidades Centrales Científico-Técnicas
1996
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 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.
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...
In the last campaign, TJ-II heliac has been operated under lithium-coated walls, representing first stellarator ever working these boundary conditions. Enhanced density control and discharge reproducibility, leading to drastic enlargement of operational window, have obtained. A strong decrease in recycling together with changes shot by fuelling characteristics wall particle inventory recorded. These changes, associated new scenario, had led a long-lasting good control. The conditions were...
This paper describes a series of experiments performed in TJ-II stellarator with the aim studying influence magnetic configuration on stability and transport properties plasmas. Plasma potential profiles have been measured several configurations up to plasma core heavy ion beam probe diagnostic. Low-order rational surfaces positioned at different radii observing effect features. edge turbulent has studied that are marginally stable due decreased well. Results show dynamical coupling between...
A direct comparison of the electric potential and its fluctuations in T-10 tokamak TJ-II stellarator is presented for similar plasma conditions two machines, using heavy ion beam probe diagnostic. We observed following similarities: (i) potentials several hundred volts, resulting a radial field E r tens V cm −1 ; (ii) negative sign at central line-averaged electron densities larger than , with comparable values both even when different heating methods; (iii) increasing density n e or energy...
Alfvén eigenmode (AE) activity driven by NBI-produced fast ions is observed in TJ-II plasmas. A two-step response of the measured AEs to electron cyclotron heating (ECH) power seen. In a first step, continuous character unstable changes chirping marginally when moderate values ECH are applied NBI-only-heated plasma. second significant reduction AE amplitude doubled. This stabilizing effect has been experimentally confirmed both on shot-by-shot basis and along single discharge means...
Recent experimental results show that the core electron temperature in TJ-II stellarator almost doubles previously obtained values for same heating power. These plasmas, heated with cyclotron waves, are characterized by their low density, and having highly peaked profiles flat, or even hollow, density profiles. The conditions obtaining these high discharges regarding injected power dependence on plasma species described. Neoclassical transport analyses performed discharges, showing a...
A physically intuitive, highly symmetric coupling of two van der Pol oscillators is considered here. The structure the equilibrium points and discrete symmetries model equations are discussed. For some combinations parameters, infinitely many appear evidence presented pointing to existence infinite periodic trajectories. complete characterization dynamics done on three specific cases, as a function parameters. It found that several attractors coexist in phase space, either having symmetry or...
The influence of plasma density and edge gradients on the development perpendicular sheared flow has been investigated in region TJ-II stellarator. naturally occurring velocity shear layer requires a minimum density. Experimental findings have shown that there is coupling between onset an increase level turbulence; once fully developed fluctuations turbulent transport slightly decreases whereas increases. Electron profiles show broadening evolution as increases above critical value where...
The heavy ion beam probe diagnostic is used in the TJ-II stellarator to study directly plasma electric potential with good spatial (up 1 cm) and temporal 2 μs) resolution. Singly charged ions, Cs+, energies of up 125 keV are column from edge core. Both electron cyclotron resonance heating (ECRH) neutral injection (NBI)-heated plasmas (PECRH = 200 400 kW, PNBI ENBI 28 keV) have been studied.Low-density ECRH [[over bar]n (0.5 1.1) × 1019 m-3] characterized by positive on order 1000 V. A...
This paper presents an overview of experimental results and progress made in investigating density control using Li-coating, transport L–H transitions TJ-II. The Li-coating changes drastically the plasma–wall interaction, decreasing recycling, enlarges substantially operational range device delaying appearance radiative collapse that happens for higher densities, which permits confinement properties much denser plasmas to be studied. Moreover, mode transition has only been achieved after...
Perturbative transport experiments have been performed at the stellarator TJ-II. Both inward propagation of edge cooling pulses induced by injection nitrogen, and outward heat due to spontaneous spikes central temperature analysed. It has found that observed is incompatible with diffusive models. Simultaneous eliminates an explanation in terms a pinch. A numerical simulation resistive interchange turbulence model suggests related successive destabilizations pressure gradient driven modes...
A system of two coupled van der Pol oscillators showing multistable behavior for some control parameter ranges is studied. When several attractors coexist a rich fractal structure found both on the border between basins and in extended zones phase space. In such strong mixing self-similar are manifest. relationship observed appearance symmetric properties attraction basins. First return maps, Poincar\'e sections, probability distribution functions have been computed model equations,...
Abstract 2D plasma potential ϕ distribution was measured in the electron cyclotron resonance heating (ECRH) and neutral beam injection (NBI) plasmas of TJ-II stellarator with heavy ion probe for whole radial range wide area poloidal angle, supported by Langmuir data at edge. The operation domain on-axis ECRH explored ( <?CDATA ${\bar n_{\text{e}}}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mover> <mml:mi>n</mml:mi>...
The influence of limiter biasing on plasma confinement, turbulence and flows is investigated in the TJ-II stellarator. Experimental results show that it possible to modify global confinement edge parameters with both positive negative biasing. Significant minor modifications structure fluctuations have been observed during transition improved regimes induced by These evidence electric field via multiple mechanisms. investigation relaxation potential fields shows two different characteristic...
In this article, the recent installed multiposition Thomson scattering (TS) of TJ-II stellarator is presented. Light from a pulsed ruby laser scattered by free electrons plasma and led to spectrometer for spectral analysis. The Doppler broadened spectrum light analyzed with in Littrow configuration, detected GaAsP image intensifier recorded two intensified charged coupled device cameras. Values electron temperature (Te) range 50 eV up 4 keV can be measured at 160 spatial elements 2.25 mm...
This paper presents an overview of experimental results and progress made in investigating the role magnetic configuration on stability transport TJ-II stellarator. Global confinement studies have revealed a positive dependence energy rotational transform plasma density, together with different parametric dependences for metallic boronized wall conditions. Spontaneous biasing-induced improved transitions, some characteristics that resemble those previously reported H-mode regimes other...
The effect of edge biasing on plasma potential was investigated in the TJ-II stellarator and T-10 tokamak. Heavy Ion Beam Probe (HIBP) diagnostic, a unique tool for studying core directly, used both machines. Experiments show that it is possible to modify global confinement parameters with limiter biasing, illustrating direct impact radial electric fields properties. For first time shown column can be charged as whole hot, near-reactor-relevant plasma. evolve two different characteristic...
Plasma potential and turbulent particle flux ΓE×B in the plasma core were measured for first time during L–H/H–L transitions TJ-II heliac using a heavy ion beam probe. The L–H transition is characterized by simultaneous drop ∼−100 V over whole radius, formation of density pedestal strong radial electric field Er between −100 to −150 cm−1 edge (0.8 < ρ 0.9), suppression broadband oscillations plasma.
Dedicated experiments have been carried out for a systematic comparison of turbulence wavenumber spectra and perpendicular rotation velocity measured at poloidally separated positions on the same flux-surface in stellarator TJ-II. The rationale behind this study is twofold, namely, validation spatial localization instabilities predicted by gyrokinetic simulations stellarators electrostatic potential variation flux surface as calculated neoclassical codes its possible impact radial electric...
Abstract TJ-II stellarator results on modelling and validation of plasma flow asymmetries due to on-surface potential variations, fuelling physics, Alfvén eigenmodes (AEs) control stability, the interplay between turbulence neoclassical (NC) mechanisms liquid metals are reported. Regarding neoclassically predicted asymmetries, its impact radial electric field along flux surface has been successfully validated against Doppler reflectometry measurements. Research physics core with pellets...
ELM-like activity has been recently observed in TJ-II, plasmas with stored energy above 1 kJ. The plasma is to develop bursts of magnetic (seen Mirnov coil signals) which are followed by a large and distinct spike the Hα signal. An increase electrostatic fluctuations at edge cold pulse towards centre also characteristics these events. In addition, electron temperature profile locally flattens radius where range 100-200 eV. This flattening can be explained terms enhanced heat conductivity....