A. Messiaen
A5049745301- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Dust and Plasma Wave Phenomena
- Antenna Design and Analysis
- Gyrotron and Vacuum Electronics Research
- Electromagnetic Simulation and Numerical Methods
- Electromagnetic Scattering and Analysis
- Atomic and Molecular Physics
- Nuclear reactor physics and engineering
- Nuclear Physics and Applications
- Laser-induced spectroscopy and plasma
- Solar and Space Plasma Dynamics
- Electromagnetic Launch and Propulsion Technology
- Energy Harvesting in Wireless Networks
- Advanced Antenna and Metasurface Technologies
- Geophysical Methods and Applications
- Meteorological Phenomena and Simulations
- High voltage insulation and dielectric phenomena
- Induction Heating and Inverter Technology
- Diamond and Carbon-based Materials Research
Royal Military Academy
2013-2023
Laboratoire de Physique des Plasmas
1997-2021
Max Planck Institute for Plasma Physics
2016
Max Planck Society
2016
École Normale Supérieure - PSL
1966-2015
Belgian Development Agency
2013
Culham Science Centre
2007-2012
CEA Cadarache
2011
CEA DAM Île-de-France
2011
Polytechnic University of Turin
2009-2011
Edge radial electric fields were induced in the edge of TEXTOR tokamak by means a polarization electrode order to study their influence on plasma profiles and its confinement. The studies include generation H-mode behaviour with either positive or negative polarity. Particle confinement (τp) deuterium impurity ions as well energy (τE) are investigated. For which remain below threshold for L-H transition, an interesting regime reduced particle without noticeable loss is found. A strong...
The European DEMO is a pulsed device with pulse length of 2 hours. functions devoted to the heating and current drive system are: plasma breakdown, ramp-up flat-top where fusion reactions occur, control during phase, finally ramp-down. EU-DEMO project was in Pre-Concept Design Phase 2014-2020, meaning that some cases, design values precise requirements from physics point view were not yet frozen. A total 130 MW considered for all phases plasma: flat top, 30 required neoclassical tearing...
The next step in the Wendelstein stellarator line is large superconducting device 7-X, currently under construction Greifswald, Germany. Steady-state operation an intrinsic feature of stellarators, and one key element 7-X mission to demonstrate steady-state plasma conditions relevant for a fusion power plant. device, on hand, requires implementation special technologies, giving rise technical challenges during design, fabrication assembly such device. On other also physics development at...
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 performance on plasma of the antennas proposed ITER ICRF system is evaluated by means antenna 24 × impedance matrix provided TOPICA code and confirmed interpreted semi-analytical ANTITER II (summarized in an appendix). From this analysis following characteristics can be derived: (1) a roughly constant power capability entire 40–55 MHz frequency band with same maximum voltage eight feeding lines obtained for all considered heating current drive phasings account broadbanding effect service...
Coating of the walls TEXTOR with silicon has led to improved tokamak plasma performance. Very low concentrations C, B, and O are measured. Radiation from is located at periphery r/a\ensuremath{\ge}0.75 decreases increasing density. Density limits enhanced by 30% as compared boronized conditions; large density gradients electron temperatures edge (10 eV) obtained. The confinement regimes observed earlier densities...
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...
The plasma sheath existing between an antenna ana a surrounding layer plays essential role. It is predicted that, for given operating frequency, there exist certain densities which the system resonant, and this very strongly enhanced radiation fully confirmed by experiments.
This paper summarizes the operational experience of ion cyclotron resonant frequency (ICRF) ITER-like antenna on JET aiming at substantially increasing power density in range requirements for ITER combined with load resiliency. An in-depth description its commissioning, aspects and achieved performances is presented.
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...
A rigorous formalism for the computation of impedance finite-length ICRH antennae is derived i n which proper care taken a correct description antenna ends. The results are compared with those obtained from previous infinite-length calculations. ensuing modification wave spectrum imposed on plasma and end effects lead to important changes respect earlier results. In particular, substantial decrease coupling predicted short wide designs.
The reference design for the ICRF antenna of ITER is constituted by a tight array 24 straps grouped in eight triplets. matching network must be load resilient operation ELMy discharges and have spectrum control heating or current drive operation. resilience based on use either hybrid couplers conjugate-T circuits. However, mutual coupling between triplets at low expected loading strongly counteracts control. Using mock-up with adjustable water solutions are designed. These derived from...
The performance of an ICRH system depends on the coupling capabilities antenna to inhomogeneous plasma profile in front it. aim this study is understand key physics phenomena contributing coupling. It shown that following density characteristics are decisive: (i) distance between and wave cutoff density, (ii) position optimum with respect one (iii) gradient leading from bulk. At each step analysis approximate relations derived loading due compared isotropic dielectric medium view application...
The current status of the mechanical and electromagnetic design for ICRF antenna system W7-X is presented. Two plugins are discussed: one consisting a pair straps with pre-matching to cover first frequency band, 25–38 MHz, second two short strap triplets band around 76 MHz. This paper focusses on lower band. Power coupling reference plasma profile studied help codes TOPICA Microwave Studio that deliver scattering matrix needed optimization geometric parameters box. Radiation power spectra...
Abstract For the central heating of a fusion reactor ion cyclotron radio frequency (ICRH) is first choice method as it able to couple RF power ions without density limit. The drawback this problem excitation magneto-sonic wave through plasma boundary layer from antenna located along wall, exceeding its voltage standoff. amount coupling depends on and surface admittance at output due profile. paper deals with optimization by use sections traveling-wave antennas (TWAs) distributed all wall...
A study of radio frequency (RF) field excitation in the edge plasma DEMO is performed by means semi-analytic coupling code ANTITER II. The modeling uses designed antenna and a reference low density profile ITER. results show existence coaxial modes propagating between wall Alfvén resonance region where surface are excited leading to large standing wave patterns all around machine. these can be strongly reduced for strap current distribution array which fulfills two conditions (Ii: i, Si:...
Long wavelength turbulence as well heat and momentum transport are significantly reduced in the DIII-D tokamak [Plasma Physics Controlled Nuclear Fusion Research (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] a result of neon seeding low confinement mode negative central shear discharge. Correspondingly, energy time increases by up to 80%. Fully saturated measurements near ρ=0.7 (ρ=r/a) wave number range 0.1⩽k⊥ρs⩽0.6, obtained with beam emission spectroscopy, exhibit...
The recent development of real-time measurements and control tools in JET has enhanced the reliability reproducibility relevant ITER scenarios. Diagnostics such as charge exchange, interfero-polarimetry, electron cyclotron emission have been upgraded for measurements. In addition, processes like magnetic equilibrium q profile reconstruction developed applied successfully experiments using model based techniques. Plasma operation against magnetohydrodynamic instabilities are also benefiting...
An overview of the results obtained so far for radiative I-mode regime on upgraded Torus Experiment Technology Oriented Research (TEXTOR-94) [Proceedings 16th IEEE Symposium Fusion Engineering (Institute Electrical and Electronics Engineers, Piscataway, NJ, 1995), Vol. 1, p. 470] is given. This under quasistationary conditions with edge neon seeding in a pumped limiter tokamak circular cross section. It combines high confinement β (up to normalized beta, βn=2) low q values (down qa=2.8)...