A5065119190- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Solar and Space Plasma Dynamics
- Semiconductor materials and devices
- Nuclear reactor physics and engineering
- Fluid Dynamics and Turbulent Flows
- Advanced Data Storage Technologies
- Nuclear Materials and Properties
- Nuclear Physics and Applications
- Physics of Superconductivity and Magnetism
- Laser-induced spectroscopy and plasma
- Silicon and Solar Cell Technologies
- Semiconductor Quantum Structures and Devices
- Dust and Plasma Wave Phenomena
- Electrostatic Discharge in Electronics
- Advancements in Semiconductor Devices and Circuit Design
- Metallurgical Processes and Thermodynamics
- Silicon Carbide Semiconductor Technologies
- Atomic and Subatomic Physics Research
- Meteorological Phenomena and Simulations
University of California, San Diego
2016-2025
Lawrence Livermore National Laboratory
2000-2022
General Atomics (United States)
1998-2022
École Polytechnique Fédérale de Lausanne
2021-2022
Sandia National Laboratories
2016-2022
National Centre for Nuclear Research
2021
National Agency for New Technologies, Energy and Sustainable Economic Development
2021
University of Toronto
2007-2018
Princeton Plasma Physics Laboratory
2006-2016
Oak Ridge National Laboratory
2006-2016
A stochastic magnetic boundary, produced by an applied edge resonant perturbation, is used to suppress most large edge-localized modes (ELMs) in high confinement ($H$-mode) plasmas. The resulting $H$ mode displays rapid, small oscillations with a bursty character modulated coherent 130 Hz envelope. transport barrier and core are unaffected the despite threefold drop toroidal rotation. These results demonstrate that boundaries compatible may be attractive for ELM control next-step fusion tokamaks.
Large Type-I edge localized modes (ELMs) are completely eliminated with small n = 3 resonant magnetic perturbations (RMP) in low average triangularity, , plasmas and ITER similar shaped (ISS) plasmas, relevant collisionalities . Significant differences the RMP requirements properties of ELM suppressed found when comparing two triangularities. In ISS current required to suppress ELMs is approximately 25% higher than triangularity plasmas. It also that width q95 window for suppression smaller...
This paper reviews measurements of edge plasma turbulence in toroidal magnetic fusion devices with an emphasis on recent results tokamaks. The dominant feature is a high level broadband density fluctuations relative amplitude δn/n ∼ 5–100%, accompanied by large potential and electron temperature fluctuations. frequency range this ∼10 kHz–1 MHz, the size scale typically ∼0.1–10 cm perpendicular to field but many metres along field, i.e. structure nearly that 2D 'filaments'. Large intermittent...
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...
Intermittent plasma objects (IPOs), featuring higher pressure than the surrounding plasma, are responsible for ∼50% of E×BT radial transport in scrape off layer (SOL) Doublet III D (DIII-D) tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] L- and H-mode discharges. Conditional averaging reveals that IPOs positively charged feature internal poloidal electric fields up to 4000 V/m. The move radially with E×BT/B2 velocities ∼2600 m/s near last closed flux surface (LCFS), ∼330 wall. slow down...
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 two-dimensional radial vs poloidal structure and motion of edge turbulence in the National Spherical Torus Experiment (NSTX) were measured using high-speed imaging visible light emission from a localized neutral gas puff. Edge images are shown analysed for Ohmic, L- H-mode plasma conditions. often show regions strong known as 'blobs', which move both poloidally radially at typical speed ≈105 cm s−1, sometimes spatially periodic features.
Metallic mirrors will be used in ITER for optical diagnostics working different spectral ranges. Their properties change with time due to erosion, deposition, and particle implantation. First tests of molybdenum were performed the DIII-D divertor under deposition-dominated conditions. Two sets recessed 2cm below floor private flux region exposed a series identical, lower-single-null, ELMing (featuring edge localized modes) H-mode discharges detached plasma conditions both legs. The first set...
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...
Dust production and accumulation present potential safety operational issues for the ITER. diagnostics can be divided into two groups: of dust on surfaces in plasma. Diagnostics from both groups are employed contemporary tokamaks; new suitable ITER also being developed tested. is likely to occur hidden areas, e.g., between tiles under divertor baffles. A novel electrostatic detector monitoring these regions has been tested at PPPL. In DIII-D tokamak include Mie scattering Nd:YAG lasers,...
Large sub-millisecond heat pulses due to Type-I edge localized modes (ELMs) have been eliminated reproducibly in DIII-D for periods approaching nine energy confinement times (τE) with small dc currents driven a simple magnetic perturbation coil. The current required eliminate all but few isolated ELM impulses during coil pulse is less than 0.4% of plasma current. Based on field line modelling, the fields resonate flux surfaces across most pedestal region (0.9 ⩽ ψN 1.0) when q95 = 3.7 ± 0.2,...
A quantitative comparison of the fluctuation-induced energy flux with total has been made in edge region TEXT tokamak using fluctuation measurements from Langmuir, heavy-ion-beam, and magnetic probes. At all but lowest densities convected due to electrostatic fluctuations dominates losses caused by plasma transport. Energy loss through is insignificant region.
National Spherical Torus Experiment [which M. Ono et al., Nucl. Fusion 40, 557 (2000)] high-power divertor plasma experiments have shown, for the first time, that benefits from lithium coatings applied to facing components found previously in limited plasmas can occur also diverted configurations. Lithium were with pellets injected into helium discharges, and an oven directed a collimated stream of vapor toward graphite tiles lower center stack divertor. depositions few milligrams 1g been...
In this paper the manipulation of power deposition on divertor targets at DIII-D by application resonant magnetic perturbations (RMPs) for suppression large type-I edge localized modes (ELMs) is analysed. We discuss modification ELM characteristics RMP applied. It shown that width pattern in ELMy H-mode depends linearly deposited energy, whereas phase discharge those patterns are controlled externally induced perturbation. was also found heat transport due to small, plasma pedestal electron...
Experiments on HL-2A, DIII-D and EAST show that turbulence just inside the last closed flux surface (LCFS) acts to reinforce existing sheared ExB flows in this region.This flow drive gets stronger as heating power is increased L-mode, leads development of a strong oscillating shear which can transition into H-mode regime when rate energy transfer from exceeds threshold.These effects become compressed time during an L-H transition, but key role turbulent still observed.The results compare...
DIII-D experiments on rapid shutdown runaway electron (RE) beams have improved the understanding of processes involved in RE beam control and dissipation. Improvements feedback enabled stable confinement out to volt-second limit ohmic coil, as well enabling a ramp down zero current. Spectroscopic studies shown that neutrals tend be excluded from centre. Measurements energy distribution function indicate broad with mean order several MeV peak energies 30–40 MeV. The appears more skewed...
Divertor detachment is explored on the TCV tokamak in alternative magnetic geometries. Starting from typical single-null shapes, poloidal flux expansion at outer strikepoint varied by a factor of 10 to investigate X-divertor characteristics, and total 70 study properties super-X divertor. The effect an additional X-point near target investigated divertors. Detachment studied these plasmas during Ohmic density ramps with ion B drift away primary X-point. threshold, depth detachment, stability...
Abstract The tokamak à configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system address critical issues in preparation for ITER a fusion power plant. For the 2019–20 campaign configurational flexibility has been enhanced with installation of removable divertor gas baffles, diagnostic capabilities an extensive set upgrades new dual frequency gyrotrons. baffles reduce coupling between main chamber allow detailed...
Self-consistent full-size turbulent-transport simulations of the divertor and SOL existing tokamaks have recently become feasible. This enables direct comparison turbulence against experimental measurements. In this work, we perform a series diverted Ohmic L-mode discharges on TCV tokamak, building first-of-a-kind dataset for validation edge models. dataset, referred to as TCV-X21, contains measurements from 5 diagnostic systems -- giving total 45 1- 2-D observables in two toroidal magnetic...
Edge conditions in DIII-D are being quantified order to provide insight into the physics of H mode regime. Several studies show that electron temperature is not key parameter controls L-H transition. Gradients edge and pressure much more promising candidates for elements such parameters. They systematically increase during L phases discharges which make a transition mode, these increases typically larger than underlying quantities. The quality confinement strongly correlated with height...
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...
Experiments in the tokamaks TEXTOR, CASTOR, T-10 and ISTTOK, as well reversed field pinch RFX have provided new complementary evidence on physics of universal mechanism E×B velocity shear stabilization turbulence, concomitant transport barrier formation radial conductivity by using various edge biasing techniques.
High-speed high-spatial-resolution data obtained by the gas puff imaging (GPI) diagnostic on National Spherical Torus Experiment [M. Ono, M.G. Bell, R.E. Bell et al. Plasma Phys. Control. Fusion 45, A335 (2003).] is analyzed and interpreted in light of recent theoretical models for electrostatic edge turbulence blob propagation. The experiment described terms regimes that predict different dependencies radial velocity convection. Using GPI data, atomic physics analysis, tracking a restricted...
Far Scrape-Off Layer (SOL) and near-wall plasma parameters in DIII-D depend strongly on the discharge confinement regime. In L-mode discharges cross-field transport increases with average density flattens far SOL profiles, thus increasing contact low field side (LFS) main chamber wall. H-mode between edge localized modes (ELMs) plasma–wall is weaker than L-mode. During ELM fluxes of particles heat to LFS wall increase transiently above values. Depending conditions, ELMs are responsible for...
Externally applied magnetic fields are used on the Texas Experimental Tokamak (TEXT) to study possibility of controlling particle, impurity and heat fluxes at plasma edge. Fields with toroidal mode number n = 2 or 3 multiple poloidal numbers m (dominantly 7) used, a poloidally toroidally averaged ratio radial field components 〈|br/Bø〉 ≅0. 1%. Calculations show that it is possible produce mixed islands stochastic regions edge (r/a ≥ 0.8) without affecting interior. The expected structure...