A5078881494- Magnetic confinement fusion research
- Fusion materials and technologies
- Nuclear Materials and Properties
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Nuclear reactor physics and engineering
- Semiconductor materials and devices
- Laser-induced spectroscopy and plasma
- Diamond and Carbon-based Materials Research
- Nuclear Physics and Applications
- Metal and Thin Film Mechanics
- Silicon and Solar Cell Technologies
- Dust and Plasma Wave Phenomena
- Ion-surface interactions and analysis
- Solar and Space Plasma Dynamics
- Metallurgical Processes and Thermodynamics
- Atomic and Subatomic Physics Research
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Data Storage Technologies
- Advanced materials and composites
- Atomic and Molecular Physics
- Nuclear materials and radiation effects
University of California, San Diego
2016-2025
General Atomics (United States)
2001-2024
Financial University
2022
Oak Ridge National Laboratory
2016-2021
Lawrence Livermore National Laboratory
2016-2018
Sandia National Laboratories California
2018
Oak Ridge Associated Universities
2018
Knoxville College
2018
University of Tennessee at Knoxville
2018
Princeton Plasma Physics Laboratory
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.
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...
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...
This paper reviews recent results of the study dust in magnetic fusion devices. Assessment role current devices and ITER is presented. Dust diagnostics, main experimental results, different theoretical aspects plasmas, as well comparison estimates numerical simulations with available data are discussed. Some limitations models dust–plasma interactions gaps approaches to considered. Possible directions for further advancements suggested.
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,...
Recent research in scrape-off layer (SOL) and divertor physics is reviewed; new existing data from a variety of experiments have been used to make cross-experiment comparisons with implications for further ITER. Studies the region near separatrix addressed relationship profiles turbulence as well scaling parallel power flow. Enhanced low-field side radial transport implicated driving flows inboard side. The medium-n nature edge localized modes (ELMs) has elucidated measurements determined...
The key remaining physics design issue for the ITER tungsten (W) divertor is question of monoblock (MB) front surface shaping in high heat flux target areas actively cooled targets. Engineering tolerance specifications impose a challenging maximum radial step between toroidally adjacent MBs 0.3 mm. Assuming optical projection parallel loads, magnetic shadowing these edges required if quasi-steady state melting to be avoided under certain conditions during burning plasma operation and...
A low amplitude (δbr∕BT=1 part in 5000) edge resonant magnetic field perturbation with toroidal mode number n=3 and poloidal numbers between 8 15 has been used to suppress most large type I localized modes (ELMs) without degrading core plasma confinement. ELMs have suppressed for periods of up 8.6 energy confinement times when the safety factor q95 is 3.5 4. The are replaced by packets events (possibly II ELMs) small amplitude, narrow radial extent, a higher level density fluctuations,...
Abstract The understanding and prediction of silicon carbide (SiC) material evolution exposed to SOL plasma conditions is prime interest because SiC represents a promising main chamber wall plasma-facing for next-step fusion devices (low hydrogenic diffusion, good mechanical thermal properties under neutron irradiation). Gross net Si erosion rates from surfaces in contact with well-diagnosed L-mode the DIII-D tokamak have been simulated surface concentrations impurities tracked as function...
The evolution of the runaway electron (RE) energy distribution function fε during massive gas injection into centered post-disruption plateaus has been reconstructed. Overall, is found to be much more skewed toward low than predicted by avalanche theory. reconstructions also indicate that RE pitch angle θ not uniform, but tends large at energies and small ∼ 0.1–0.2 high energies. Overall power loss from plateau appears dominated collisions with background free bound electrons, leading line...
It is important to develop a predictive capability for the tungsten source rate near strike points during H-mode operation in ITER and beyond. deuterium plasma exposures were performed on W-coated graphite molybdenum substrates DIII-D divertor using DiMES. The W-I 400.9 nm spectral line was monitored by fast filtered diagnostics cross calibrated via high-resolution spectrometer resolve inter-ELM W erosion. effective ionization/photon (S/XB) unique method developed based surface analysis....
Small/type-II edge-localized-modes (ELMs), carrying 1% of the plasma stored energy, are found to deposit only 45 ± 5% ELM power near strike point, and remaining 55 far scrape-off-layer (SOL). Small ELMs spread their over a larger area compared type-I ELMs, where such ratio is about 60% 40% for near- far-SOL regions, respectively. The reflected in heat flux width (λq) SOL intra-small profile 6.0 mm, almost factor 2 than that 3.15 similar conditions magnetic configuration. At peak, small λq be...
Abstract The thermo-mechanical response of an ATJ graphite sample to controlled runaway electron (RE) dissipation, realized in DIII-D, is modelled with a novel work-flow that features the RE orbit code KORC, Monte Carlo particle transport Geant4 and finite element multiphysics software COMSOL. KORC provides striking positions momenta, calculates volumetric energy deposition COMSOL simulates thermoelastic response. Brittle failure predicted according maximum normal stress criterion, which...
Experimental analysis at DIII-D shows that small edge localized modes (ELMs) deposit a larger fraction of their energy to the first wall, compared type-I ELMs in similar magnetic configuration and input power. The (λQ) particle (λΓ) flux decay lengths scrape-off layer (SOL) are up 3 5 times larger, respectively, for than ELMs. Transport dynamics ELM filaments SOL found be related divertor conditions, where high collisionality, typical partially detached plasmas, is associated with increased...
Abstract Post-disruption runaway electron (RE) kinetic energy K and pitch angle sin are critical parameters for determining resulting first wall material damage during strikes, but very challenging to measure experimentally. During the final loss instability, confined RE reconstructed center-post strikes both high impurity (high-Z) low (low-Z) plasmas by combining soft x-ray, hard synchrotron emission, total radiated power measurements. Deconfined (wall impacting) sinθ is then these shots...
A particle balance analysis was conducted during a deuterium (D2) shattered pellet injection-induced plasma shutdown on the DIII-D tokamak to determine why less than 20% of material is assimilated into core by mid-current quench (CQ). Initially, most D2 injected as frozen shards and ionized upon entering vessel. During thermal quench, particles move divertors subsequently center post (CP) walls, where they rapidly recycle partially accumulate neutrals without assimilating plasma. In...
Impurity deposition and mixing during gas jet-initiated plasma shutdown is studied using a rapid ({approx}2 ms), massive ({approx}10{sup 22} particles) injection of neon or argon into stationary DIII-D H-mode discharges. Fast-gated camera images indicate that the bulk jet neutrals do not penetrate far pedestal. Nevertheless, high ({approx}90%) thermal quench radiated power fractions are achieved; this appears to be facilitated through combination fast ion heat transport, both driven by...
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...
Studies of naturally occurring and artificially introduced carbon dust are conducted in DIII-D TEXTOR. In DIII-D, does not present operational concerns except immediately after entry vents. Submicrometre sized is routinely observed using Mie scattering from a Nd : Yag laser. The source strongly correlated with the presence type I edge localized modes (ELMs). Larger size (0.005–1 mm diameter) by optical imaging, showing elevated levels Inverse dependence velocity on inferred found imaging...
Transport and turbulence profiles were directly evaluated using probes for the first time in edge scrape-off layer (SOL) of NSTX [Ono et al., Nucl. Fusion 40, 557 (2000)] low (L) high (H) confinement, power (Pin∼ 1.3 MW), beam-heated, lower single-null discharges. Radial turbulent particle fluxes peak near last closed flux surface (LCFS) at ≈4×1021 s−1 L-mode are suppressed to ≈0.2×1021 H mode (80%–90% lower) mostly due a reduction density fluctuation amplitude phase between radial velocity...