A5055584461- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Fusion materials and technologies
- Plasma Diagnostics and Applications
- Atomic and Subatomic Physics Research
- Nuclear reactor physics and engineering
- Geomagnetism and Paleomagnetism Studies
- Dust and Plasma Wave Phenomena
- Gas Dynamics and Kinetic Theory
- Stellar, planetary, and galactic studies
- Fluid Dynamics and Turbulent Flows
- Gyrotron and Vacuum Electronics Research
- Astronomical Observations and Instrumentation
- Model Reduction and Neural Networks
- Particle Accelerators and Free-Electron Lasers
- Computational Physics and Python Applications
- Neural Networks and Applications
- GNSS positioning and interference
- Target Tracking and Data Fusion in Sensor Networks
- Quantum Chromodynamics and Particle Interactions
- Flow Measurement and Analysis
Universidad Carlos III de Madrid
2011-2024
Universidad Complutense de Madrid
1995-2008
Unidades Centrales Científico-Técnicas
1996-2008
Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas
1996-2008
Kyoto University
2007
Australian National University
2004-2007
Fusion for Energy
2002-2006
Oak Ridge National Laboratory
2003
Princeton Plasma Physics Laboratory
2003
International collaboration on development of a stellarator confinement database has progressed. More than 3000 data points from nine major experiments have been compiled. Robust dependences the energy time density and heating power confirmed. Dependences other operational parameters, i.e. minor radii, magnetic field rotational transform , evaluated using inter-machine analyses. In order to express in unified scaling law, systematic differences each subgroup are quantified. An posteriori...
Numerical results for the three mono-energetic transport coefficients required a complete neoclassical description of stellarator plasmas have been benchmarked within an international collaboration. These are flux-surface-averaged moments solutions to linearized drift kinetic equation which determined using field-line-integration techniques, Monte Carlo simulations, variational method employing Fourier–Legendre test functions and finite-difference scheme. The benchmarking has successfully...
The improvement of core electron heat confinement has been realized in a wide range helical devices such as CHS, LHD, TJ-II and W7-AS. Strongly peaked temperature profiles large positive radial electric field, E r , the region are common features for this improved confinement. Such observations consistent with transition to ‘electron-root’ solution ambipolarity condition context neoclassical transport, which is unique non-axisymmetric configurations. Based on background, collectively dubbed...
A Doppler reflectometer system has recently been installed in the stellarator TJ-II. The is optimized for Q-band (33–50 GHz) and high-curvature plasmas produced launch angle of microwave beam can be controlled by a steerable mirror to obtain angles between ±20° enabling measurement perpendicular wave numbers range 3–15 cm−1. available angular allows comparisons positive negative values additionally calibration system. Localization k⊥-estimation done via three-dimensional ray/beam-tracing...
The benchmarking of the thermal neoclassical transport coefficients is described using examples Large Helical Device (LHD) and TJ-II stellarators. are evaluated by energy convolution monoenergetic obtained direct interpolation or neural network techniques from databases precalculated different codes. temperature profiles calculated a predictive code balance equations with ambipolar radial electric field estimated diffusion equation to guarantee unique smooth solution, although several...
A new generally applicable method to solve differential equations, based on neural networks, is proposed. Straightforward implement, finite differences and coordinate transformations are not used. The network provides a flexible compact base for representing the solution, found through global minimization of an error functional. As proof principle, two-dimensional ideal magnetohydrodynamic plasma equilibrium solved. Since no particular topology assumed, technique especially promising...
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.
Advanced stellarators require convoluted modular coils to produce a plasma with satisfactory performance. Moreover, the number of is sometimes high decrease ripple created by coils. For reactor stellarators, these requirements imply relatively small ports for in-vessel access and maintenance, i.e. in comparison tokamaks. The blankets divertor modules will have be replaced periodically (about each 1-4 years depending on design) due neutron damage, also erosion targets. Blanket are activated,...
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...
The neoclassical transport properties of TJ-II stellarator [C. Alejaldre et al., Fusion Technol. 13, 521 (1988)] are studied with the monoenergetic Monte Carlo technique. A compromise between number modes and particles required computing time to obtain reliable estimates, from computational point view, diffusion coefficients is shown be one thousand hundred harmonics, because rich magnetic-field structure TJ-II. Although, these requirements probably too demanding in making estimations. data...
The capabilities of the Joint European Torus (JET) electron cyclotron emission (ECE) diagnostics have recently been extended with an upgrading heterodyne radiometer. number channels has doubled to 96 channels, a frequency separation corresponding <1 cm for JET magnetic field gradient, and response 1 MHz. This enhancement increased radial coverage ECE temperature measurements in approximately full plasma column (limited at R>2.6 m X-mode due harmonic overlap) almost all values...
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....
Ion temperatures have been measured in the TJ-II stellarator using passive emission spectroscopy parallel and perpendicular directions. A high-energy component was observed from tails of Hα line both directions, suggesting a non-negligible population suprathermal ions. The role this fast ion energy component, which has tokamak plasmas when heated by electron cyclotron resonance heating additional plasma bulk is investigated means simple model. origin such discussed terms different mechanisms.
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...
Numerous observation exist of a population high energetic ions with energies well above the corresponding thermal values in plasmas generated by electron cyclotron resonance (ECR) heating TJ-II stellarator and other magnetically confined devices. In this work we study impact ECR different conditions (positions powers) on fast escaping from stellarator. For study, an ion luminescent probe operated counting mode is used to measure energy distribution suprathermal ions, range 1 30 keV. It...
AbstractAbstractThe characteristics of core electron-root confinement (CERC) in helical devices are illustrated using results from four different experiments: the Compact Helical System, Large Device, TJ-II, and Wendelstein 7-AS. Common features include strongly peaked electron temperature profiles large positive radial electric fields Er region for discharges with sufficient central cyclotron heating (ECH). Such observations consistent a transition to solution ambipolarity condition Er,...
The International Stellarator Confinement Database (ISCDB) is a joint effort of the helical device community. It publicly available at http://www.ipp.mpg.de/ISS and http://iscdb.nifs.ac.jp. validity physics models investigated employing ISCDB data. Bayesian model comparison shows differences in confinement scaling data subgroups. Theory-based assessment pure neoclassical transport regimes, however, indicates scalability which supported by experimental results specific W7-AS scenarios....
The goal of this work is to study the empirical behaviour suprathermal ions in electron cyclotron resonance heating (ECRH) and neutral-beam injection (NBI) phases TJ-II stellarator. Our approach combines passive emission spectroscopy, which detects confined with energies up hundreds electronvolts, a luminescent probe operated as multichannel fast-ion energy spectrometer using pulse height analysis, ⩾1 keV that escape from plasma. We will present data taken density power scans ECRH plasmas...
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...
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....
Neoclassical transport theory describes local diffusive transport. For those magnetic configurations where this approach is valid it has the benefit of being independent plasma profiles. In contrast for many particle orbits have large deviations from their birth surface, non-local contributions to flux be considered. work a newly developed Monte Carlo code been used compute global ion fluxes same parameters two devices with very different configurations, namely Wendelstein 7-X helias, which...
Electron cyclotron resonance heating (ECRH) has become an attractive technique in today's fusion experiments not only as a mechanism but also diagnostic tool and way to induce controllable currents through electron current drive (ECCD). In this paper we show, using ray tracing simulations, how one can address all these issues with the ECRH system designed for TJ-II stellarator. This set up consists of two 500 kW gyrotrons at f = 53.2 Ghz coupled plasma quasi-optical transmission lines,...
Fine structures are found in the TJ-II stellarator electron temperature and density profiles, when they measured using a high spatial resolution Thomson scattering system. These consist of peaks valleys superimposed to smooth average. Some irregularities remain an ensemble average discharges with similar macroscopic parameters such as line density, central temperature, plasma current. They all magnetic configurations explored plasmas heated by cyclotron waves. Their characteristics shown...
Enhanced confinement is observed in neutral beam injector (NBI)-heated hydrogen discharges made the stellarator TJ-II after injection of a single cryogenic fuel pellet into plasma core. In addition to expected increase electron density, ne, core (PI), diamagnetic energy content seen rise, with respect similar without PI, by up 40%. Furthermore, time, τEdiag, as determined using loop, enhanced when compared predictions obtained International Stellarator Scaling law [H. Yamada et al., Nucl....
A transient behaviour is observed in the plasma core of TJ-II stellarator with fast drops electron temperature. Changes line-averaged density are synchronized temperature drops. This phenomenon appears plasmas created and heated using 300 kW cyclotron heating high power density. The resembles both, electric pulsation discovered CHS `electron root' feature reported by W7-AS team. flexibility low magnetic shear have permitted identification current as control parameter for appearance this...