A5062177973- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Fluid Dynamics and Turbulent Flows
- Plasma Diagnostics and Applications
- Laser-induced spectroscopy and plasma
- Theoretical and Computational Physics
- Geomagnetism and Paleomagnetism Studies
- Complex Systems and Time Series Analysis
- Characterization and Applications of Magnetic Nanoparticles
- Atomic and Subatomic Physics Research
- Semiconductor materials and devices
- Meteorological Phenomena and Simulations
- Nuclear Materials and Properties
- Advanced Data Storage Technologies
- Ion-surface interactions and analysis
- Advancements in Semiconductor Devices and Circuit Design
- Mass Spectrometry Techniques and Applications
- Laser Design and Applications
- Quantum chaos and dynamical systems
- Advanced Thermodynamics and Statistical Mechanics
American University of Beirut
2013-2024
Japan External Trade Organization
2015
CEA Cadarache
1999-2013
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
1999-2013
University of California, San Diego
2001-2007
Max Planck Society
2007
Molina Center for Energy and the Environment
2004
Centre National de la Recherche Scientifique
1998-2000
École Polytechnique
1998-2000
Intermittent plasma objects (IPOs) featuring higher pressure than the surrounding plasma, and responsible for ∼50% of E×BT radial transport, are observed in scrape off layer (SOL) edge DIII-D tokamak [J. Watkins et al., Rev. Sci. Instrum. 63, 4728 (1992)]. Conditional averaging reveals that IPOs, produced at a rate ∼3×103 s−1, positively charged also polarized, poloidal electric fields up to 4000 V/m. The IPOs move poloidally speeds 5000 m/s radially with E×BT/B2 velocities ∼2600 near last...
Probe measurements in the PISCES linear device indicate presence of plasma radially far from where it is produced. We show that this mainly caused by large-scale structures with high radial velocity. Data Tore Supra tokamak striking similarities shape these intermittent events as well fluctuation density probability distribution and frequency spectrum. The fact intermittent, are so similar devices tokamaks indicates universality convective transport magnetically confined plasmas.
The nature of intermittency, long observed in magnetic fusion devices, was revisited lately [G. Antar et al., Phys. Rev. Lett. 87, 065001 (2001)]. It shown that intermittency is caused by large-scale events with high radial velocity reaching about 1/10th the sound speed. These type structures were named “avaloids.” In present article, universality convective turbulence magnetically confined plasmas investigated. Turbulence properties scrape-off layer four different devices are compared....
Abstract WEST is an MA class superconducting, actively cooled, full tungsten (W) tokamak, designed to operate in long pulses up 1000 s. In support of ITER operation and DEMO conceptual activities, key missions are: (i) qualification high heat flux plasma-facing components integrating both technological physics aspects relevant particle exhaust conditions, particularly for the monoblocks foreseen divertor; (ii) integrated steady-state at confinement, with a focus on power issues. During phase...
Cross-field fluctuation-driven transport is studied in edge and scrape-off layer (SOL) plasmas the DIII-D tokamak using a fast reciprocating Langmuir probe array allowing local measurements of particle heat fluxes. Two different non-diffusive mechanisms that can contribute strongly to cross-field SOL high-density discharges are identified compared. The first these involves intermittent events observed at plasma separatrix SOL. Intermittence has qualitatively similar character L-mode ELM-free...
Experimental results from a magnetized argon plasma column demonstrate controlled transition to turbulent state as the magnetic field (B) strength is increased. At lower B there an onset of fluctuations in density and potential. These are shown be due drift waves that have been modified by flow shear. As increased character undergoes several changes. changes include general decrease coherence, increase phase lag (between potential), straightening observed dispersion relation. Concomitantly,...
Density fluctuation measured by a reciprocating Langmuir probe on the Tore Supra tokamak [Garbet et al., Nucl. Fusion 32, 2147 (1992)] is investigated. The purpose of this article to give rather comprehensive analysis intermittency using several data analyses compare bursts properties that coherent structures and avalanches. probability distribution density fluctuations found positively skewed, while Gaussian shape for negative values recorded. It shown spectra possess one scaling region...
Recent experiments in the Current Drive Experiment-Upgrade (CDX-U) provide a first-ever test of large area liquid lithium surfaces as tokamak first wall to gain engineering experience with metal and investigate whether very low recycling plasma regimes can be accessed walls. The CDX-U is compact (R = 34 cm, 22 Btoroidal 2 kG, IP 100 kA, Te(0)∼ eV, ne(0) ∼ 5 × 1019 m−3) spherical torus at Princeton Plasma Physics Laboratory. A toroidal pool limiter an 2000 cm2 (half total limiting surface)...
A combination of recently installed state-of-the-art imaging and profile diagnostics, together with established plasma simulation codes, are providing for the first time on Mega Ampère Spherical Tokamak (MAST) tools required studying confinement transport, from core through to edge scrape-off-layer (SOL). The H-mode transport barrier is now routinely turned off using a poloidally localized fuelling fine balancing X-points. Theory, supported by experiment, indicates that radial electric field...
High-pressure noble gas jet injection is a mitigation technique which potentially satisfies the requirements of fast response time and reliability, without degrading subsequent discharges. Previously reported experiments on DIII-D showed good success at reducing deleterious disruption effects. In this paper, results recent Alcator C-Mod are reported. Jointly, these have greatly improved understanding dynamics processes involved in mitigating both machines, sequence events following observed...
A fast imaging camera is used to unveil the spatio-temporal properties of radially convective events in CSDX linear plasma device [M. J. Burin et al., Phys. Plasmas, 12, 052320 (2005)]. The exposure time set 1μs and between frames 10μs. series from a Langmuir probe pixel 50000-frame movie are compared cross-correlated. Excellent agreement two diagnostics found for spatial scales greater than 2.5mm. fluctuations inside main column change different poloidal mode numbers as function time....
Deuterium pellets have been injected into plasmas in the DIII-D tokamak from inner wall, top, and outer midplane port locations to investigate fuelling efficiency, mass deposition interaction with edge localized modes (ELMs). Pellets (low field side (LFS)) show a large discrepancy profile efficiency conventional pellet ablation theory, while penetration depth compares favourably theory. The wall top is deeper than expected measurements indicate that deposited inside measured radius, thus...
Lower hybrid current drive (LHCD) experiments with line-averaged density varying between 1.5 × 1019 and 6 m−3 are performed on the Tore Supra tokamak under quasi-steady-state conditions respect to fast electron dynamics. The LHCD efficiency is analysed from bremsstrahlung (FEB) cyclotron emission (ECE). effect of plasma equilibrium particle fuelling documented. It concluded that decay FEB could be consistent simple scaling FEB. Plasma edge measurements presented looking for emission. In a...
The parallel Kelvin–Helmholtz instability is investigated as a possible explanation for poloidal asymmetries of density fluctuations which reverse with the plasma current direction. It shown that these modes are localized around position where radial gradient velocity maximum. Two mechanisms lead to unstable modes; acceleration ions in presheath and anomalous Stringer spin-up due particle flux. Up–down explained by combining two effects. Depending on limiter configuration, effect amplifies...
A radially sheared azimuthal flow is observed in a cylindrical helicon plasma device without any apparent external sources of angular momentum input. Broadband fluctuations combined with chain coherent structures are observed, turbulent particle transport across the shear layer inhibited, and energy appears to be transferred from linearly unstable intermediate wave numbers into both larger smaller spatial scales that stable. The shape radial potential profile associated agreement published...
Abstract The mission of WEST (tungsten-W Environment in Steady-state Tokamak) is to explore long pulse operation a full tungsten (W) environment for preparing next-step fusion devices (ITER and DEMO) with focus on testing the ITER actively cooled W divertor tokamak conditions. Following successful completion phase 1 (2016-2021), 2 started December 2022 lower made entirely ITER-grade mono-blocks. A boronization prior first plasma attempt allowed smooth startup new divertor. Despite reduced...
Recently, reversed magnetic shear operation was performed using only ion-cyclotron-resonance frequency minority heating (ICRH) during current ramp-up. A wide region of has been obtained. For the first time, an electron internal transport barrier sustained by ICRH is observed, with a dramatical drop density fluctuations. This maintained, on flat top, for about 2 s.
The goal of this article is to show that the “intermittent” convective transport in scrape-off layer (SOL) linear magnetic confinement plasmas actually takes place periodically. This reflected several features are unveiled article. It found distribution time between high-amplitude bursts, selected above a given threshold, has central frequency SOL. Moreover, similar one taken inside main plasma column as threshold reduced, suggesting links SOL and column. power spectrum radial flux...
Massive injection of argon was used to terminate DIII-D discharges with different radial profiles the safety factor q. An increasing delay before onset central temperature collapse observed as overall (core and edge) q target plasma increased. Additionally, an increase in length current quench time observed, consistent reduced magnetohydrodynamic (MHD) mode amplitudes MHD mixing. These results are supported by measurements heat impurity mixing during thermal which observe that transport not...
Recently, it was shown that intermittency observed in magnetic fusion devices is caused by large-scales events with high radial velocity reaching about 1∕10th of the sound speed (called avaloids or blobs) [G. Antar et al., Phys. Rev. Lett. 87 065001 (2001)]. In present paper, poloidal distribution turbulence investigated on Mega-Ampère Spherical Tokamak [A. Sykes Plasmas 8 2101 To achieve our goal, target probes span divertor strike points are used and one reciprocating probe at midplane....