A5033441765- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
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- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Nuclear reactor physics and engineering
- Plasma Diagnostics and Applications
- Atomic and Molecular Physics
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- Nuclear Materials and Properties
- Nuclear Physics and Applications
- Advanced Chemical Physics Studies
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- Electron and X-Ray Spectroscopy Techniques
- Neonatal Health and Biochemistry
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- Nuclear Engineering Thermal-Hydraulics
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Forschungszentrum Jülich
2014-2024
Royal Military Academy
1993-2020
CEA Cadarache
2015
ITER
2015
Culham Science Centre
2008-2015
Max Planck Institute for Plasma Physics
2003-2015
Centre National de la Recherche Scientifique
2015
Aix-Marseille Université
2015
Japan External Trade Organization
2014-2015
Max Planck Society
2011
Progress in the area of MHD stability and disruptions, since publication 1999 ITER Physics Basis document (1999 Nucl. Fusion 39 2137–2664), is reviewed. Recent theoretical experimental research has made important advances both understanding control tokamak plasmas. Sawteeth are anticipated baseline ELMy H-mode scenario, but tools exist to avoid or them through localized current drive fast ion generation. Active other instabilities will most likely be also required ITER. Extrapolation from...
Type-I edge-localized modes (ELMs) have been mitigated at the JET tokamak using a static external $n=1$ perturbation field generated by four error correction coils located far from plasma. During application of ELM frequency increased factor 4 and amplitude ${\mathrm{D}}_{\ensuremath{\alpha}}$ signal decreased. The energy loss per normalized to total stored energy, $\ensuremath{\Delta}W/W$, dropped values below 2%. Transport analyses shows no or only moderate (up 20%) degradation confinement...
A survey has been carried out into the causes of all 2309 disruptions over last decade JET operations. The aim this was to obtain a complete picture possible disruption causes, in order devise better strategies prevent or mitigate their impact. analysis allows effort avoid be more efficient and effective. As expected, highly complex pattern chain events that led emerged. It found majority had technical root cause, for example due control errors, operator mistakes. These bring random,...
The provision of a particle and power exhaust solution which is compatible with first-wall components edge-plasma conditions key area present-day fusion research mandatory for successful operation ITER DEMO. work package plasma-facing (WP PFC) within the European programme complements laboratory experiments, i.e. in linear plasma devices, electron ion beam loading facilities, studies performed toroidally confined magnetic such as JET, ASDEX Upgrade, WEST etc. connection both groups done via...
We present the results of experiments in JET to study effect plasma shape on high density ELMy H-modes, with geometry magnetic boundary similar that envisaged for standard Q = 10 operation ITER. The described are single lower null plasmas, q profile, neutral beam heating and gas fuelling, average triangularity δ calculated at separatrix ~0.45-0.5 elongation κ~1.75. In agreement previous obtained other divertor Tokamaks, thermal energy confinement time maximum achievable steady state a given...
Recent experiments on JET have shown that type-I edge localized modes (ELMs) can be controlled by the application of static low n = 1 external magnetic perturbation fields produced four error field correction coils (EFCC) mounted far away from plasma between transformer limbs. When an with amplitude a few mT at (the normalized poloidal flux, ?, is larger than 0.95) applied during stationary phase ELMy H-mode plasma, ELM frequency rises ~30?Hz up to ~120?Hz. The energy loss per total stored...
Recent results from an ITPA joint experiment to study the onset, growth, and decay of relativistic electrons (REs) indicate that loss mechanisms other than collisional damping may play a dominant role in dynamics RE population, even during quiescent Ip flattop. Understanding physics growth mitigation is motivated by theoretical prediction disruptions full-current (15 MA) ITER discharges could generate up 10 MA REs with 10–20 MeV energies. The MHD group conducting measure detection threshold...
Stationary high energy confinement is observed on TEXTOR-94 for times limited only by the flux swing of transformer using strong edge radiation cooling. Necessary tools are feedback control radiated power and plasma content. At highest densities obtained (up to 1.2 Greenwald limit), exceeds edge-localized-mode-free H-mode scaling ITERH93-P more than 20%. β limits reached with fH89/qa≈0.6. No detrimental effect seeded impurity seen. These discharges meet many conditions necessary a fusion...
Impurity injection in the JET ELMy H-mode regime has produced high-confinement, quasi-steady-state plasmas with densities close to Greenwald density. However, at large Ar densities, a sudden loss of confinement is observed. A possible correlation between and observed MHD phenomena, both core edge plasma, was considered. The degradation coincided impurity profile peaking following disappearance sawtooth activity. In addition, density analysis confirmed that central modes prevented peaking....
The main objective of this paper is investigation methods for reduction divertor heat loads in order to increase the lifetime tiles future fusion reactors.Special emphasis given studies transient due edge localized modes (ELMs).Two are compared: argon seeded type-I ELMy H-modes and nitrogen type-III H-modes.In both scenarios, impurity seeding leads a pedestal energy hence released by ELM.This consequentially reduces power load targets.At high radiative fractions H-modes, part that ELM (small...
The dynamic ergodic divertor (DED) on the TEXTOR tokamak allows for creation of static and rotating helical magnetic perturbation fields. In 3/1 configuration strong m/n = 2/1 sideband excites a locked tearing mode above critical field strength. onset threshold depends strongly plasma fluid rotation with respect to mode. Rotation in current direction destabilizes certain range frequencies, whereas counter-rotation has stabilizing influence. shows minimum when frequency external equals MHD
The geodesic acoustic mode (GAM) is a high frequency branch of zonal flows, which observed in toroidal plasmas. Because curvature effects, density fluctuations are excited, investigated with the $O$-mode correlation reflectometer at TEXTOR. This Letter reports on poloidal distribution GAM induced fluctuation and compares them theoretical predictions. influence flows ambient turbulence studied, too.
Plasma disruptions affect plasma-facing and structural components of tokamaks due to electromechanical forces, thermal loads generation high energy runaway electrons (REs). Asymmetries in poloidal halo toroidal plasma current can now be routinely measured four positions 90° apart. Their assessment is used validate the design ITER vessel support system its in-vessel components. The challenge disruption comes from both short duration over which a large has lost potential for asymmetries. focus...
Bumpiness in a magnetic field enhances the magnitude of plasma viscosity and increases rate flow damping. A general solution neoclassical toroidal (NTV) torque induced by nonaxisymmetric perturbation (NAMP) collisionless regimes tokamaks is obtained this Letter. The angular momentum can be strongly changed, when there small deviation symmetry caused NAMP order 0.1% strength.
Magnetic turbulence is observed at the beginning of current quench in intended TEXTOR disruptions. Runaway electron (RE) suppression has been experimentally found magnetic larger than a certain threshold. Below this threshold, generated RE inversely proportional to level turbulence. The originates from background plasma and amplitude depends strongly on toroidal field density. These results explain previously threshold for generation have be considered predictions ITER.
Recent progress in experimental and theoretical studies of edge localized mode (ELM) physics is reviewed for the reactor relevant plasma regimes, namely high confinement that is, H-modes advanced scenarios.
This paper describes experiments with highly shaped JET H-mode plasmas, which were directed to developing regimes where Type I ELMs are replaced by other edge relaxations, while maintaining the pedestal pressure of ELMy H-modes. It was found that II coexisted I, up densities order Greenwald limit, III appear, and good confinement lost. Only at highest collisionality it observed completely replace I. At high βp q95, 'grassy' completely. The MHD spectra characteristics for grassy significantly...
The first results of the Dynamic Ergodic Divertor in TEXTOR, when operating m/n=3/1 mode configuration, are presented. deeply penetrating external magnetic field perturbation this configuration increases toroidal plasma rotation. Staying below excitation threshold for m/n=2/1 tearing mode, rotation is always direction current, even if projection rotating opposite direction. observed consistent with a radial electric field, generated by an enhanced electron transport ergodic layers near...
Controlled experiments on the suppression of m/n = 2/1 tearing mode with electron cyclotron heating and current drive in TEXTOR are reported. The was produced reproducibly by an externally applied rotating perturbation field, allowing a systematic study its suppression. Heating inside island is shown to be dominant mechanism these experiments. An extrapolation findings ITER indicates that projected system for could significantly more effective than present estimates indicate, which only...
We have analysed the edge stability of JET discharges with small localized modes (ELMs) using high resolution Thomson scattering system for accurate profiles in equilibrium reconstruction. For reference plasmas large Type I ELMs we confirm results from earlier analyses that is limited by intermediate-n peeling–ballooning a relatively radial extent. The double null configuration needed to replace smaller II considerably increases against these while n = ∞ ballooning not affected. When this...
A strong toroidal rotation braking has been observed in plasmas with application of an n = 1 magnetic perturbation field on the JET tokamak. Calculation results from momentum transport analysis show that torque induced by a global profile. The maximal value this is at plasma core region (ρ < 0.4) and it about half neutral beam injection torque. calculation shows mainly regime core, but close to transition between 1/ν regimes. neoclassical viscosity (NTV) regimes calculated. magnitude NTV...
JOREK 3D non-linear MHD simulations of a D2 Massive Gas Injection (MGI) triggered disruption in JET are presented and compared detail to experimental data. The MGI creates an overdensity that rapidly expands the direction parallel magnetic field. It also causes growth islands (m/n=2/1 3/2 mainly) seeds 1/1 internal kink mode. O-points all island chains (including 1/1) located front MGI, consistently with observations. A burst activity peak plasma current take place at same time as...
The radiative improved (RI) mode is a tokamak regime offering many attractive reactor features. In the article, RI of TEXTOR-94 shown to follow same scaling as linear ohmic confinement and thus identified one most fundamental operational regimes. current understanding derived from experiments modelling conditions necessary for sustaining reviewed, are mechanisms leading L-RI transition. article discusses compatibility high impurity seeding with low central power density burning reactor, well...
Improved confinement is achieved on TEXTOR under high power conditions (up to 4 MW of additional heating with NBI-co+ICRH, NBI-co+counter or NBI-co+counter+ICRH) edge radiative cooling employing silicon neon as the radiating impurities. It shown that in quasi-stationary up 85% input can be radiated. Such fractions offer possibility utilizing these techniques facilitate exhaust problem for a Tokamak reactor. Discharges exhibit enhanced properties at densities, e.g. central line averaged...