A5047239782- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Fusion materials and technologies
- Solar and Space Plasma Dynamics
- Gyrotron and Vacuum Electronics Research
- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- Nuclear reactor physics and engineering
- Atomic and Molecular Physics
- Dust and Plasma Wave Phenomena
- Laser-induced spectroscopy and plasma
- High-Energy Particle Collisions Research
- Plasma and Flow Control in Aerodynamics
- Quantum optics and atomic interactions
- Physics of Superconductivity and Magnetism
- Computational Fluid Dynamics and Aerodynamics
- Advanced Frequency and Time Standards
- Magneto-Optical Properties and Applications
- Mass Spectrometry Techniques and Applications
- Fluid Dynamics and Turbulent Flows
- Electrostatic Discharge in Electronics
Dutch Institute for Fundamental Energy Research
2014-2024
Max Planck Institute for Plasma Physics - Greifswald
2018
University of Stuttgart
2016
Leiden University
2016
Eindhoven University of Technology
2012-2016
Max Planck Institute for Plasma Physics
2003-2016
Leiden Observatory
2016
University of Exeter
2016
Japan External Trade Organization
2015
Institute for Atomic and Molecular Physics
2005-2014
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...
JOREK is a massively parallel fully implicit non-linear extended MHD code for realistic tokamak X-point plasmas. It has become widely used versatile studying large-scale plasma instabilities and their control developed in an international community. This article gives comprehensive overview of the physics models implemented, numerical methods applied solving equations studies performed with code. A dedicated section highlights some verification work done hierarchy different available...
The onset of a neoclassical tearing mode (NTM) depends on the existence large enough seed island. It is shown in Joint European Torus that NTMs can be readily destabilized by long-period sawteeth, such as obtained sawtooth stabilization from ion-cyclotron heating or current drive. This has important implications for burning plasma scenarios, alpha particles strongly stabilize sawteeth. also that, adding and drive just outside inversion radius, sawteeth are destabilized, resulting shorter...
Optimal design and use of electron cyclotron heating requires that accurate relatively quick computer codes be available for prediction wave coupling, propagation, damping current drive at realistic levels EC power. To this end, a number have been developed in laboratories worldwide. A detailed comparison these is desirable since they variety methods modelling the behaviour effects waves. The approach used benchmarking study to apply small representative cases. Following minor remedial work...
In tokamak plasmas with a tearing mode, strong scattering of high power millimeter waves, as used for heating and noninductive current drive, is shown to occur. This new wave phenomenon be related the passage $O$ point magnetic island through beam. The density determines detailed phasing scattered radiation relative $O$-point passage. depends strongly nonlinearly on beam power.
Anomalous scattering of high power millimetre waves from gyrotrons at 140 and 110 GHz is investigated for plasma with rotating islands TEXTOR. The magnetic field density influence the spectral content scattered their levels significantly. strong occurs in two regimes, one low densities densities, that also depend on field. regimes are separated by a quiescent regime without anomalous scattering. Investigations suggest high-density generated low-field side intersection gyrotron beam island...
A selection of achievements and first physics results are presented the European Integrated Tokamak Modelling Task Force (EFDA ITM-TF) simulation framework, which aims to provide a standardized platform an integrated modelling suite validated numerical codes for prediction complete plasma discharge arbitrary tokamak.The framework developed by ITM-TF, based on generic data structure including both simulated experimental data, allows development sophisticated simulations (workflows)...
Experiments with strong localized electron cyclotron heating (ECH) in the RTP tokamak show that heat transport is governed by alternating layers of good and bad thermal conduction. For central deposition hot filaments are observed inside q = 1 radius. Moving ECH resonance from centre to edge plasma results discrete steps temperature. The transitions occur when minimum value crosses 1,2,5/2 or 3, correspond loss a barrier situated close rational value. Close new type sawtooth activity...
Here we present the first measurements by collective Thomson scattering of evolution fast-ion populations in a magnetically confined fusion plasma. 150 kW and 110 Ghz radiation from gyrotron were scattered TEXTOR tokamak plasma with energetic ions generated neutral beam injection ion cyclotron resonance heating. The temporal behavior spatially resolved velocity distribution is inferred received radiation. dynamics at sawteeth slowdown after switch off auxiliary heating time. latter shown to...
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 suppression of (neoclassical) tearing modes is great importance for the success future fusion reactors like ITER. Electron cyclotron waves can suppress islands, both by driving noninductive current in island region and heating island, causing a perturbation to Ohmic plasma current. This Letter reports on experiments TEXTOR tokamak, investigating effect heating, which usually neglected. unique set tools available TEXTOR, notably dynamic ergodic divertor create islands with fully known...
Abstract A review is given on the highlights of a scatter-shot approach developing machine-learning methods and artificial neural networks based fast predictors for application to fusion exhaust. The aim enable facilitate optimized improved modeling allowing more flexible integration physics models in light extrapolations towards future devices. project encompasses various research objectives: (a) developments surrogate model power & particle exhaust plants; (b) assessments...
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...
Neoclassical tearing modes (NTMs) are magnetohydrodynamic that can limit the performance of high β discharges in a tokamak, leading eventually to plasma disruption. A NTM is sustained by perturbation ‘bootstrap’ current, which consequence pressure flattening across magnetic island. Control and suppression this mode be achieved means electron cyclotron waves (ECWs) allow deposition highly localized power at island location. The ECW replenishes missing bootstrap current generating either...
The stability of tearing modes is analysed for current density profiles with a small, well localized, additional around the resonant mode rational surface. parameter Δ' calculated perturbative treatment current. For case Gaussian profile current, this shown to lead simple and illustrative condition amount required stabilization. consequences are analysed. In particular, dependence effect on its exact location clearly shown. co-driven far less than in counter-driven
With the dynamic ergodic divertor in TEXTOR fundamental effects of coupling external magnetic field perturbations to confined plasma have been studied. The non-linear between (m/n = 12/4) and internal modes 3/1) has investigated. critical perturbation for excitation an m/n 2/1 tearing mode depends not only on magnitude but also direction toroidal angular momentum input by neutral beam injection (NBI). Below threshold this a spin-up observed, which strength field. It is independent both...
The stability and performance of tokamak plasmas are limited by instabilities such as neoclassical tearing modes. This paper reports on an experimental proof principle a feedback control approach for real-time, autonomous suppression stabilization modes in tokamak. system combines electron cyclotron emission diagnostic sensing the same sight line with steerable resonance heating current drive (ECRH/ECCD) antenna. A methodology fast detection q = m/n 2/1 retrieval their location, rotation...
A heuristic criterion for the full suppression of an NTM was formulated as η ≡ j CD,max / BS ⩾ 1.2 (Zohm et al 2005 J. Phys. Conf. Ser. 25 234), where is maximum in driven current density profile applied to stabilize mode and local bootstrap density. In this work we subject a systematic theoretical analysis on basis generalized Rutherford equation. Taking into account only effect CD inside island, new by minimum total obtained form allowed value width current, w dep , combined with required...
Experimental investigations of sawteeth interaction with fast ions measured by collective Thomson scattering on TEXTOR are presented. Time-resolved measurements localized 1D fast-ion distribution functions allow us to study dynamics during several sawtooth cycles. Sawtooth oscillations interact strongly the population in a wide range plasma parameters. Part ion phase space density oscillates out oscillation hydrogen neutral beam injection (NBI). These most likely originate from energies...
At the ASDEX Upgrade tokamak electron temperature (Te) profile is estimated from cyclotron emission (ECE) using radiation transport forward modeling within integrated data analysis scheme. For interpretation of ECE measurements in high plasmas, it was necessary to upgrade model with a fully relativistic absorption coefficient including Maxwell–Jüttner distribution. This intrinsically enables affected by so-called 'pseudo radial displacement' or harmonic overlap. A numerically efficient...
Abstract Neutral gas physics and neutral interactions with the plasma are key aspects of edge divertor in a fusion reactor including detachment phenomenon often seen as to dealing power exhaust challenges. A full description dynamics requires 6D kinetic approach, potentially time dependent, where details wall geometry play substantial role, extent that, e.g., subdivertor region has be included. The Monte Carlo (MC) approach used for about 30 years EIRENE (Reiter et al 2005 Fusion Sci....
An electron cyclotron emission (ECE) receiver inside the resonance heating (ECRH) transmission line has been brought into operation. The ECE is extracted by placing a quartz plate acting as Fabry-Perot interferometer under an angle wave (ECW) beam. measurements are obtained during high power ECRH This demonstrates successful operation of diagnostic and, in particular, sufficient suppression gyrotron component preventing it from interfering with measurements. When integrated feedback system...
A quasi-optical description of the propagation and damping slowly varying wave amplitude across an arbitrary electron cyclotron beam is presented. This model goes well beyond those implemented in existing tracing codes, which typically require spatial inhomogeneity to be small. The present allows accurate evolution region power deposition, where latter condition quite generally broken. additional physical effects from dispersion included are discussed relation their consequences for...