The Experts below are selected from a list of 16464 Experts worldwide ranked by ideXlab platform
C. Hidalgo - One of the best experts on this subject based on the ideXlab platform.
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Causality detection and turbulence in Fusion Plasmas
Nuclear Fusion, 2014Co-Authors: B. Ph. Van Milligen, C. Hidalgo, Teresa Estrada, G. Birkenmeier, Mirko Ramisch, A. AlonsoAbstract:This work explores the potential of an information-theoretical causality detection method for unravelling the relation between fluctuating variables in complex non-linear systems. The method is tested on some simple though non-linear models, and guidelines for the choice of analysis parameters are established. Then, measurements from magnetically confined Fusion Plasmas are analysed. The selected data bear relevance to the all-important spontaneous confinement transitions often observed in Fusion Plasmas, fundamental for the design of an economically attractive Fusion reactor. It is shown how the present method is capable of clarifying the interaction between fluctuating quantities such as the turbulence amplitude, turbulent flux and zonal flow amplitude, and uncovers several interactions that were missed by traditional methods.
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isotope effect and multiscale physics in Fusion Plasmas
Physical Review Letters, 2013Co-Authors: C. Hidalgo, I Shesterikov, A Kramerflecken, S Zoletnik, M Van Schoor, M VergoteAbstract:The mechanism governing the impact of the mass isotope on plasma confinement is still one of the main scientific conundrums facing the magnetic Fusion community after more than thirty years of intense research. We have investigated the properties of local turbulence and long-range correlations in hydrogen and deuterium Plasmas in the TEXTOR tokamak. Experimental findings have shown a systematic increasing in the amplitude of long-range correlations during the transition from hydrogen to deuterium dominated Plasmas. These results provide the first direct experimental evidence of the importance of multiscale physics for unraveling the physics of the isotope effect in Fusion Plasmas.
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long range correlations and edge transport bifurcation in Fusion Plasmas
Nuclear Fusion, 2011Co-Authors: D. Carralero, C. Hidalgo, M. A. Pedrosa, S Jachmich, P Manz, E Martines, B Van Milligen, M Ramisch, I ShesterikovAbstract:Recently, a European transport project has been carried out among several Fusion devices for studying the possible link between the mean radial electric field (Er), long-range correlation (LRC) and edge bifurcations in Fusion Plasmas. The main results reported in this paper include: (i) the discovery of low-frequency LRCs in potential fluctuations which are amplified during the development of edge mean Er using electrode biasing and during the spontaneous development of edge sheared flows in stellarators and tokamaks. Evidence of nonlocal energy transfer and the geodesic acoustic mode modulation on local turbulent transport have also been observed. The observed LRCs are consistent with the theory of zonal flows described by a 'predator–prey' model. The results point to a significant link between the LRC and transport bifurcation. (ii) Comparative studies in tokamaks, stellarators and reversed field pinches have revealed significant differences in the level of the LRC. Whereas the LRCs are clearly observed in tokamaks and stellarators, no clear signature of LRCs was seen in the RFX-mod reversed field pinch experiments. These results suggest the possible influence of magnetic perturbations on the LRC, in agreement with recent observations in the resonant magnetic perturbation experiments at the TEXTOR tokamak. (iii) The degree of the LRCs is strongly reduced on approaching the plasma density-limit in tokamaks and stellarators, suggesting the possible role of collisionality or/and the impact of mean Er × B flow shear on zonal flows.
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Multi-scale physics mechanisms and spontaneous edge transport bifurcations in Fusion Plasmas
EPL (Europhysics Letters), 2009Co-Authors: C. Hidalgo, M. A. Pedrosa, C. Silva, D. Carralero, E. Ascasibar, B. A. Carreras, Teresa Estrada, Francisco L. Tabarés, D. Tafalla, J. GuaspAbstract:The magnitude of radial transport in magnetic confinement devices for controlled nuclear Fusion suffers spontaneous bifurcations when specific system parameter values are exceeded. Here we show, for the first time, that the correlation length of the plasma potential becomes of the order of the machine size during the edge bifurcation itself, quite unlike the density fluctuations. The mechanism governing the development of this bifurcation, leading to the establishment of an edge transport barrier, is still one of the main scientific conundrums facing the magnetic Fusion community after more than twenty years of intense research. The results presented here show the dominant role of long-range correlations when approaching the Low to High confinement edge transition in Fusion Plasmas. This is in line with the expectation that multi-scale interactions are a crucial ingredient of complex dynamics in many non-equilibrium systems.
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On the physics of plasma rotation in Fusion Plasmas
AIP Conference Proceedings, 2008Co-Authors: C. HidalgoAbstract:A view of the mechanisms underlying momentum transport in Fusion Plasmas devices is presented. Heat and energy transport in Fusion Plasmas is partly due to turbulent processes having an intermittent character and presenting some universal features. The investigation of the mechanisms underlying the generation of plasma flows (via turbulence and neoclassical effects) is key area of research to control transport in magnetically confined Plasmas. Projections of ITER plasma performance require better understanding of plasma rotation.
Ulrich Stroth - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of the tilt angle of turbulent structures in the core of Fusion Plasmas
Nuclear Fusion, 2019Co-Authors: Javier Pinzon, Ulrich Stroth, Teresa Estrada, Pascale Hennequin, T. Happel, Clemente Angioni, Alexander Lebschy, The Asdex Upgrade TeamAbstract:The tilt angle of turbulent structures stands for the anisotropy of turbulence which is essential for understanding the dynamics of magnetized Plasmas. It is a quantity predicted by theory and simulations, that provides information on the interplay between turbulence, micro-instabilities and plasma flows. A new method for measuring the tilt angle of turbulent structures in the core region of Fusion Plasmas using Doppler reflectometry is presented. First measurements of this type on the ASDEX Upgrade tokamak have shown a significant difference of tilt angle for different plasma conditions. The dominance of sheared flows in determining the structure tilt is experimentally demonstrated for different turbulence regimes.
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Three-dimensional dynamics of turbulence in the edge of Fusion Plasmas
2007Co-Authors: N. Mahdizadeh, Ulrich Stroth, Mirko Ramisch, Franko Greiner, Alexander Kendl, Bruce D. Scott, Theoretische PhysikAbstract:Introduction Different turbulence simulations show that the drift wave is a possible candidate to explain the turbulence in the edge of Fusion Plasmas. The important properties of drift-wave turbulence are a cross phase between density and potential fluctuations smaller than π/4 and a finite parallel wavenumber k‖. Furthermore, the key element of the drift wave is the parallel electron dynamics. It can couple the drift wave to the shear-Alfven wave and determines the degree of instability and the level of transport. On the other hand, the turbulence dynamics parallel to the magnetic field is strongly coupled to the perpendicular dynamics. Therefore, a detailed understanding of drift waves requires fully three-dimensional investigations, i.e. of the dynamics perpendicular and parallel to the magnetic field. The toroidal low-temperature plasma in the torsatron TJ-K is dimensionally similar to the one in the edge of Fusion Plasmas [1]. In contrast to Fusion Plasmas, the whole plasma volume in TJ-K is accessible to Langmuir probes. This allows the use of probe arrays with a large number of tips and high temporal and spatial resolution. A further advantage of the device is that its plasma can be simulated by turbulence codes such as GEM3 [2]. In this paper, the perpendicular dynamics of turbulence is studied with the focus on the poloidal wavenumber spectra and the turbulent transport. For the first time, the parallel dynamics of turbulence has been investigated in the core of a toroidally confined plasma. The results of the parallel wavenumber and the parallel propagation velocity are compared with results from the simulation code GEM3.
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EU-US Transport Task Force Workshop on Transport in Fusion Plasmas, Transport Barrier Physics
Plasma Physics and Controlled Fusion, 2001Co-Authors: J. W. Connor, Giovanni Bracco, R. J. Buttery, C. Hidalgo, A. Jacchia, A. G. Peeters, Ulrich StrothAbstract:This conference report summarizes the contributions to the EU-US workshop on Transport in Fusion Plasmas, Transport Barrier Physics held in Varenna, Italy, 4-7 September 2000. The workshop, whose main focus was on transport barriers, was organized into four sections: transport barrier physics, MHD effects concerning barriers, turbulence and core transport. This report is organized in a like manner.
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EU-US Workshop on Transport in Fusion Plasmas
Plasma Physics and Controlled Fusion, 1997Co-Authors: J. W. Connor, C. Hidalgo, A. Jacchia, F. Romanelli, Ulrich StrothAbstract:This report summarizes the contributions to the 10th EU–US Transport Task Force Workshop on Transport in Fusion Plasmas (Varenna, Italy, 6–9 September 2004). There was an emphasis on transport barrier physics, but also sessions on particle and heat pinches, electron and transient transport and electromagnetic and electrostatic turbulent transport, as well as some on other general issues.
J. W. Connor - One of the best experts on this subject based on the ideXlab platform.
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eu us transport task force workshop on transport in Fusion Plasmas transport near operational limits
Plasma Physics and Controlled Fusion, 2003Co-Authors: J. W. Connor, C. Hidalgo, X. Garbet, A. Loarte, L Giannone, M Greenwald, P ManticaAbstract:This conference report summarizes the contributions to, and discussions at, the 9th EU-US transport task force workshop on `transport in Fusion Plasmas: transport near operational limits', held in Cordoba, Spain, during 9–12 September 2002. The workshop was organized under three main headings: edge localized mode physics and confinement, profile dynamics and confinement and confinement near operational limits: density and beta limits; this report follows the same structure.
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EU-US Transport Task Force Workshop on Transport in Fusion Plasmas, Transport Barrier Physics
Plasma Physics and Controlled Fusion, 2001Co-Authors: J. W. Connor, Giovanni Bracco, R. J. Buttery, C. Hidalgo, A. Jacchia, A. G. Peeters, Ulrich StrothAbstract:This conference report summarizes the contributions to the EU-US workshop on Transport in Fusion Plasmas, Transport Barrier Physics held in Varenna, Italy, 4-7 September 2000. The workshop, whose main focus was on transport barriers, was organized into four sections: transport barrier physics, MHD effects concerning barriers, turbulence and core transport. This report is organized in a like manner.
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EU-US Workshop on Transport in Fusion Plasmas
Plasma Physics and Controlled Fusion, 1997Co-Authors: J. W. Connor, C. Hidalgo, A. Jacchia, F. Romanelli, Ulrich StrothAbstract:This report summarizes the contributions to the 10th EU–US Transport Task Force Workshop on Transport in Fusion Plasmas (Varenna, Italy, 6–9 September 2004). There was an emphasis on transport barrier physics, but also sessions on particle and heat pinches, electron and transient transport and electromagnetic and electrostatic turbulent transport, as well as some on other general issues.
Liu Chen - One of the best experts on this subject based on the ideXlab platform.
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nonlinear dynamics of phase space zonal structures and energetic particle physics in Fusion Plasmas
New Journal of Physics, 2015Co-Authors: S. Briguglio, G. Fogaccia, Fulvio Zonca, Liu Chen, G. Vlad, Xingan WangAbstract:A general theoretical framework for investigating the nonlinear dynamics of phase space zonal structures is presented in this work. It is then, more specifically, applied to the limit where the nonlinear evolution time scale is smaller or comparable to the wave–particle trapping period. In this limit, both theoretical and numerical simulation studies show that nonadiabatic frequency chirping and phase locking could lead to secular resonant particle transport on meso- or macro-scales. The interplay between mode structures and resonant particles then provides the crucial ingredient to properly understand and analyze the nonlinear dynamics of Alfven wave instabilities excited by nonperturbative energetic particles in burning Fusion Plasmas. Analogies with autoresonance in nonlinear dynamics and with superradiance in free-electron lasers are also briefly discussed.
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Energetic particles and multi-scale dynamics in Fusion Plasmas
Plasma Physics and Controlled Fusion, 2014Co-Authors: Fulvio Zonca, S. Briguglio, G. Fogaccia, Liu Chen, A. Milovanov, Zhiyong Qiu, G. Vlad, Xingan WangAbstract:The role of energetic particles (EPs) in Fusion Plasmas is unique as they could act as mediators of cross-scale couplings. More specifically, EPs can drive instabilities on the macro- and meso-scales and intermediate between the microscopic thermal ion Larmor radius and the macroscopic plasma equilibrium scale lengths. On one hand, EP driven shear Alfven waves (SAWs) could provide a nonlinear feedback onto the macro-scale system via the interplay of plasma equilibrium and Fusion reactivity profiles. On the other hand, EP-driven instabilities could also excite singular radial mode structures at SAW continuum resonances, which, by mode conversion, yield microscopic fluctuations that may propagate and be absorbed elsewhere, inducing nonlocal behaviors. The above observations thus suggest that a theoretical approach based on advanced kinetic treatment of both EPs and thermal plasma is more appropriate for burning Fusion Plasmas. Energetic particles, furthermore, may linearly and nonlinearly (via SAWs) excite zonal structures, acting, thereby, as generators of nonlinear equilibria that generally evolve on the same time scale of the underlying fluctuations. These issues are presented within a general theoretical framework, discussing evidence from both numerical simulation results and experimental observations. Analogies of Fusion Plasmas dynamics with problems in condensed matter physics, nonlinear dynamics, and accelerator physics are also emphasized.
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nonlinear dynamics of phase space zonal structures and energetic particle physics in Fusion Plasmas
arXiv: Plasma Physics, 2014Co-Authors: S. Briguglio, G. Fogaccia, Fulvio Zonca, Liu Chen, G. Vlad, Xingan WangAbstract:A general theoretical framework for investigating nonlinear dynamics of phase space zonal structures is presented in this work. It is then, more specifically, applied to the limit where the nonlinear evolution time scale is smaller or comparable to the wave-particle trapping period. In this limit, both theoretical and numerical simulation studies show that non-adiabatic frequency chirping and phase locking could lead to secular resonant particle transport on meso- or macro-scales. The interplay between mode structures and resonant particles then provides the crucial ingredient to properly understand and analyze the nonlinear dynamics of Alfv\'en wave instabilities excited by non-perturbative energetic particles in burning Fusion Plasmas. Analogies with autoresonance in nonlinear dynamics and with superradiance in free electron lasers are also briefly discussed.
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alfven waves a journey between space and Fusion Plasmas
Plasma Physics and Controlled Fusion, 2008Co-Authors: Liu ChenAbstract:Alfven waves discovered by Hannes Alfven (1942 Nature 150 405) are fundamental electromagnetic oscillations in magnetized Plasmas existing in the nature and laboratories. Alfven waves play important roles in the heating, stability and transport of Plasmas. The anisotropic nearly incompressible shear Alfven wave is particularly interesting since, in realistic non-uniform Plasmas, its wave spectra consist of both the regular discrete and the singular continuous components. In this Alfven lecture, I will discuss these spectral properties and examine their significant linear and nonlinear physics implications. These discussions will be based on perspectives from my own research in both space and laboratory Fusion Plasmas, and will demonstrate the positive feedback and cross-fertilization between these two important sub-disciplines of plasma physics research. Some open issues of nonlinear Alfven wave physics in burning Fusion as well as magnetospheric space Plasmas will also be explored.
Fulvio Zonca - One of the best experts on this subject based on the ideXlab platform.
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nonlinear dynamics of phase space zonal structures and energetic particle physics in Fusion Plasmas
New Journal of Physics, 2015Co-Authors: S. Briguglio, G. Fogaccia, Fulvio Zonca, Liu Chen, G. Vlad, Xingan WangAbstract:A general theoretical framework for investigating the nonlinear dynamics of phase space zonal structures is presented in this work. It is then, more specifically, applied to the limit where the nonlinear evolution time scale is smaller or comparable to the wave–particle trapping period. In this limit, both theoretical and numerical simulation studies show that nonadiabatic frequency chirping and phase locking could lead to secular resonant particle transport on meso- or macro-scales. The interplay between mode structures and resonant particles then provides the crucial ingredient to properly understand and analyze the nonlinear dynamics of Alfven wave instabilities excited by nonperturbative energetic particles in burning Fusion Plasmas. Analogies with autoresonance in nonlinear dynamics and with superradiance in free-electron lasers are also briefly discussed.
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Energetic particles and multi-scale dynamics in Fusion Plasmas
Plasma Physics and Controlled Fusion, 2014Co-Authors: Fulvio Zonca, S. Briguglio, G. Fogaccia, Liu Chen, A. Milovanov, Zhiyong Qiu, G. Vlad, Xingan WangAbstract:The role of energetic particles (EPs) in Fusion Plasmas is unique as they could act as mediators of cross-scale couplings. More specifically, EPs can drive instabilities on the macro- and meso-scales and intermediate between the microscopic thermal ion Larmor radius and the macroscopic plasma equilibrium scale lengths. On one hand, EP driven shear Alfven waves (SAWs) could provide a nonlinear feedback onto the macro-scale system via the interplay of plasma equilibrium and Fusion reactivity profiles. On the other hand, EP-driven instabilities could also excite singular radial mode structures at SAW continuum resonances, which, by mode conversion, yield microscopic fluctuations that may propagate and be absorbed elsewhere, inducing nonlocal behaviors. The above observations thus suggest that a theoretical approach based on advanced kinetic treatment of both EPs and thermal plasma is more appropriate for burning Fusion Plasmas. Energetic particles, furthermore, may linearly and nonlinearly (via SAWs) excite zonal structures, acting, thereby, as generators of nonlinear equilibria that generally evolve on the same time scale of the underlying fluctuations. These issues are presented within a general theoretical framework, discussing evidence from both numerical simulation results and experimental observations. Analogies of Fusion Plasmas dynamics with problems in condensed matter physics, nonlinear dynamics, and accelerator physics are also emphasized.
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nonlinear dynamics of phase space zonal structures and energetic particle physics in Fusion Plasmas
arXiv: Plasma Physics, 2014Co-Authors: S. Briguglio, G. Fogaccia, Fulvio Zonca, Liu Chen, G. Vlad, Xingan WangAbstract:A general theoretical framework for investigating nonlinear dynamics of phase space zonal structures is presented in this work. It is then, more specifically, applied to the limit where the nonlinear evolution time scale is smaller or comparable to the wave-particle trapping period. In this limit, both theoretical and numerical simulation studies show that non-adiabatic frequency chirping and phase locking could lead to secular resonant particle transport on meso- or macro-scales. The interplay between mode structures and resonant particles then provides the crucial ingredient to properly understand and analyze the nonlinear dynamics of Alfv\'en wave instabilities excited by non-perturbative energetic particles in burning Fusion Plasmas. Analogies with autoresonance in nonlinear dynamics and with superradiance in free electron lasers are also briefly discussed.
