A5058724470- Magnetic confinement fusion research
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Physics of Superconductivity and Magnetism
- Silicon and Solar Cell Technologies
- Advancements in Semiconductor Devices and Circuit Design
- Silicon Carbide Semiconductor Technologies
- Gyrotron and Vacuum Electronics Research
- Quantum and electron transport phenomena
- Electrostatic Discharge in Electronics
- High-Energy Particle Collisions Research
- Corporate Taxation and Avoidance
- Advanced battery technologies research
- Advanced Sensor and Control Systems
- Diffusion and Search Dynamics
- Nuclear reactor physics and engineering
- HVDC Systems and Fault Protection
- Advancements in Solid Oxide Fuel Cells
- Solar and Space Plasma Dynamics
- Ion channel regulation and function
- Rangeland and Wildlife Management
Aalto University
2013
École Polytechnique Fédérale de Lausanne
2005-2011
Japan Atomic Energy Agency
2008
Max Planck Institute for Plasma Physics
2008
CEA Cadarache
2008
Fusion for Energy
2008
Huazhong University of Science and Technology
2008
École Polytechnique
2007
The ITER electron cyclotron (EC) upper port antenna (or launcher) is nearing completion of the detailed design stage and final build-to-print will soon start. main objective this launcher to drive current locally stabilize neoclassical tearing modes (NTMs) (depositing ECCD inside island that forms on either q = 3/2 or 2 rational magnetic flux surfaces) control sawtooth instability (deposit near 1 surface). should be capable steering focused beam deposition location resonant surface over...
Starting from a standard single null X-point configuration, second order divertor (snowflake (SF)) has been successfully created on the Tokamak à Configuration Variable (TCV) tokamak. The magnetic properties of this innovative configuration have analysed and compared with configuration. For SF divertor, connection length flux expansion close to separatrix exceed those by more than factor 2. shear in plasma edge is also larger for
Neoclassical tearing modes (NTMs) are magnetic islands which increase locally the radial transport and therefore degrade plasma performance. They self-sustained by bootstrap current perturbed enhanced transport. The confinement degradation is proportional to island width position of resonant surface. q = 2 NTMs much more detrimental than 3/2 due their larger radii. metastable in typical scenarios with βN ⩾ 1 region where safety factor increasing radius. This fact that local pressure gradient...
This paper considers the heating mix of ITER for two main scenarios. Presently, 73 MW absorbed power are foreseen in 20/33/20 ECH, NBI and ICH. Given a sufficient edge stability, Q = 10—the goal scenario 2—can be reached with 40 irrespective method but depends sensitively inter alia on H-mode pedestal temperature, density profile shape characteristics impurity transport. ICH preferentially heats ions would contribute specifically ΔQ < 1.5. The success 5 steady-state 4 reduced current...
A predictive analysis of the capabilities ITER electron cyclotron wave system is presented in this work. Modifications both upper launcher and equatorial aimed at increasing potentialities are identified discussed. modification has already been incorporated updated front steering design called extended physics launcher. By adopting different deposition ranges for lower mirrors, offers flexibility to drive current from radial region required stabilization neoclassical tearing modes (NTM) up...
Improved electron energy confinement in tokamak plasmas, related to internal transport barriers, has been linked nonmonotonic current density profiles. This is difficult prove experimentally since usually the profiles evolve continuously and injection generally requires significant input power. New experiments are presented, which inductive used generate positive negative perturbations plasma center, with negligible These results demonstrate unambiguously for first time that can be modified...
13 MW of electron cyclotron current drive (ECCD) power deposited inside the q = 1 surface is likely to reduce sawtooth period in ITER baseline scenario below level empirically predicted trigger neoclassical tearing modes (NTMs). However, since ECCD control scheme solely predicated upon changing local magnetic shear, it prudent plan use a complementary which directly decreases potential energy kink mode order period. In event that natural longer than expected, due enhanced α particle...
On the TokamakConfiguration Variable (TCV), electron internal transport barriers (eITBs) can be formed during a gradual evolution from centrally peaked to hollow current profile while all external actuators are held constant. The formation occurs rapidly (<τeE) and locally and, according ASTRA modelling, is consistent with appearance of local minimum in safety factor (q) profile. eITB sustained by non-inductively driven currents (including off-axis bootstrap current) for many redistribution...
Simulations of the plasma current density evolution in electron internal transport barrier discharges on Tokamak à Configuration Variable (TCV) have been performed, order to determine relationship between safety-factor profile and improvement. The results show that formation is correlated with shear reversal all cases studied, regardless different heating drive schemes. No indications were found discrete effects related low-order rational q surfaces. On contrary, increase confinement along...
Electron internal transport barriers (eITBs) are obtained in TCV with different heating and current drive schemes. They sustained steady-state conditions for several energy confinement redistribution times. In these scenarios, the density profile displays a behaviour respect to normal L-mode plasmas, or without auxiliary heating. fully non-inductive discharges developing an eITB, shape is strongly correlated electron temperature profile, normalized gradient equal 0.45 times gradient,...
Important ingredients of the advanced-tokamak route to fusion have been explored in depth Tokamak à Configuration Variable [F. Hofmann, J. B. Lister, M. Anton et al., Plasma Phys. Controlled Fusion 36, B277 (1994)] over past two years. Using a uniquely powerful and flexible electron-cyclotron resonance heating (ECRH) system as primary actuator, fully noninductive, steady-state electron internal transport barrier discharges generated with an electron-energy confinement time up five times...
Electron internal transport barriers (eITBs) are generated in the TCV tokamak with strong electron cyclotron resonance heating a variety of conditions, ranging from steady-state fully noninductive scenarios to stationary discharges finite inductive component and finally transient current ramps without drive. The confinement improvement over L-mode ranges 3 6; bootstrap fraction is invariably large above 70% highest cases, good profile alignment permitting attainment steady state. Barriers...
The current density in tokamak plasmas strongly affects transport phenomena, therefore its understanding and control represent a crucial challenge for controlled thermonuclear fusion. Within the vast framework of studies, three topics have been tackled course present thesis: first, modelling evolution electron Internal Transport Barrier (eITB) discharges Tokamak Configuration Variable (TCV); second, study diffusion inversion properties observed during Swing Electron Cyclotron Current Drive...
The effect of the predicted local electron cyclotron current driven by optimized system on ITER is discussed. A design variant was recently proposed to enlarge physics program covered upper and equatorial launchers. By extending functionality range launcher, significant control capabilities sawtooth period can be obtained. launcher improvement still allows enough margin exceed requirements for neoclassical tearing mode stabilization, which it originally designed. analysis carried with ASTRA...
In the Tokamak à Configuration Variable (TCV) (Hofmann F et al1994 Plasma Phys. Control. Fusion 36 B277), global plasma oscillations have been discovered in fully non-inductively driven plasmas featuring electron internal transport barriers (ITB) with strong ECRH/ECCD. These are linked to destabilization and stabilization of MHD modes near foot ITB can lead large total current line-averaged density, among others. They intrinsically related fact that ITBs pressure gradients a region low...
Advanced scenarios exhibit improved confinement properties, which make them attractive candidate for ITER. For these to be achieved, the sustainment of transport barriers and therefore high pressure gradients is inherent. Their stability properties both in transient steady state phases a major issue [1], because relationship between performances proximity limit. Core MHD modes are one key issues development barriers, as they degrade and, worse case, disrupt plasma. The understanding...
This paper reviews the design and functionality of 24 MW 170 GHz electron cyclotron heating current drive system being planned for ITER Tokamak. The sub-systems (power supplies, gyrotrons, transmission lines launcher antennas) are described based on present day technologies, while on-going R&D provides component sub-system testing with possibility increasing reliability overall EC system. Modifications to steering ranges launching antennas under investigation that can improve functional...
The rapid formation of an electron internal transport barrier (eITB) is observed during a slow evolution (similar or equal to 200 ms) from centrally peaked hollow current density profile, while all external actuators remain constant. time constant for the appears be shorter than energy confinement time. improved associated with occurs first in localized region off-axis. Then effects propagate inner and outer flux surfaces on scale. temporal spatial localizations suggest threshold magnetic...
Generation of a Swing Electron Cyclotron Current Drive (Swing ECCD), i.e. driving alternated, symmetric, positive or negative local ECCD, during single discharge and at constant total input EC power, was performed the Tokamak à Configuration Variable (TCV).The electron temperature is observed to be modulated inside deposition radius, implying modulation transport properties.The ECCD only actuator for modifications in properties.These exhibit inverted behaviors depending on location co-and...
A two-fields model that self-consistently describes the coupled, spectral dynamics of flute mode large-scale flows turbulence is presented. This has a characteristic form 'predator–prey' system, in which populations quanta (prey), growing via linear instability, generate (predators) through Reynolds stress. Concurrently, mean flow growth regulates prey population. To understand long term nonlinear evolution this one-prey two-predator low-dimensional prototype was constructed, assuming such...
The Fokker‐Planck code CQL3D has been used to investigate the effect of radial particle diffusion on ECCD current density profiles in TCV tokamak. For two discharges with electron internal transport barriers (eITB), jcd and resulting q‐profile have calculated reconstructed. studied eITBs are kinds: fully sustained non‐inductive eITB off‐axis co‐current ECCD, or a large Ohmic on‐axis counter ECCD. It is shown that different do modify profiles, but q‐profiles less influenced due necessary...