A5007895483- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Superconducting Materials and Applications
- Dust and Plasma Wave Phenomena
- Laser-Plasma Interactions and Diagnostics
- Atomic and Molecular Physics
- Laser-induced spectroscopy and plasma
- Nuclear reactor physics and engineering
- Particle accelerators and beam dynamics
- Nuclear Materials and Properties
- Metal and Thin Film Mechanics
- Nuclear Physics and Applications
- Advanced Data Storage Technologies
- Gas Dynamics and Kinetic Theory
- Diamond and Carbon-based Materials Research
- Ion-surface interactions and analysis
- Vacuum and Plasma Arcs
- High-pressure geophysics and materials
- Semiconductor materials and devices
- Plasma Applications and Diagnostics
- High-Energy Particle Collisions Research
- Solar and Space Plasma Dynamics
- Electromagnetic Launch and Propulsion Technology
CompX (United States)
2020-2023
University of California, San Diego
2011-2020
Lawrence Livermore National Laboratory
2006-2014
Oak Ridge National Laboratory
2006-2014
University of California, Berkeley
2007
Massachusetts Institute of Technology
1996-2006
Higashihiroshima Medical Center
2006
Hiroshima University
2006
University of California, Irvine
2006
University of Washington
2006
A comprehensive investigation has been performed of the static and dynamic behaviour detached recombining plasmas in linear divertor plasma simulator NAGDIS-II. For stationary detachment, transition from electron-ion recombination (EIR) to molecular activated (MAR) observed by injecting hydrogen gas into high density helium plasmas. The particle loss rate due MAR is found be comparable that EIR. Experiments have also injection a heat pulse produced RF heating demonstrate volumetric...
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,...
The transport of dust particles in tokamak fusion devices is studied using computer simulations with the code, DUSTT. Recent developments modelling DUSTT code are reported. improved model dynamics edge plasmas takes into account several additional effects, including thermionic and secondary electron emission which affects charging heating, grain size effect on thermal radiation, presence impurities plasma. It shown that leads to enhanced heating by plasma boosts destruction particles. zone...
Volume recombination within the Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] divertor plasma is measured and found to be a significant fraction of total ion sink under detached conditions. The occurs in regions where Te∼1 eV ne∼1021 m−3. Measurements spatial distribution are presented. determinations rates made by measuring D0 Balmer spectrum using collisional radiative model describing level populations, ionization, D0. concept “recombinations per series photon”...
Dust particulates in the size range of 10nm–100μm are found all fusion devices. Such dust can be generated during tokamak operation due to strong plasma∕material-surface interactions. Some recent experiments and theoretical estimates indicate that particles provide an important source impurities plasma. Moreover, a serious threat safety next-step In this paper, experimental observations on devices reviewed. A physical model for transport simulation newly developed code DUSTT discussed. The...
Molecular activated recombination (MAR) has been clearly observed for the first time in a divertor plasma simulator. A small amount of hydrogen gas puffing into helium strongly reduced ion particle flux along magnetic field, although conventional radiative and three-body processes were quenched. Careful comparison Balmer spectra with collisional atomic molecular data indicates that population distribution over levels relatively low principal quantum numbers can be well explained by taking...
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...
Analysis of the experimental data from tokamaks and linear divertor simulators leads to conclusion that plasma recombination is a crucial element detachment. Different mechanisms relevant conditions tokamak scrape-off layer (SOL) are considered. The physics Molecular Activated Recombination (MAR) involving vibrationally excited molecular hydrogen discussed. Although conventional Electron–Ion (EIR) alone can strongly alter parameters, MAR impact be substantial for both SOL simulators....
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...
The concentrations of the ions H+, H2+, and H3+ are measured in a weakly-ionized hydrogen plasma with electron temperatures Te=3–7 eV, densities Ne=1011–1012 cm−3, background gas NH2=5×1013–1015 cm−3. relative ion using an omegatron-type mass spectrometer, while density temperature Langmuir probe together absolutely-calibrated Hα emission spectroscopy. mean lifetime is estimated from fixed wall measurements. From parameters, expected steady-state molecular modeled relevant rate balance...
It has been known for a long time that microscopic dust appears in plasmas fusion devices. Recently it was shown can be responsible the termination of long- discharges. Also, ITER-scale experiments pose safety problems related to its chemical activity, tritium retention and radioactive content. In particular, presence vacuum chamber ITER is one main concerns licensing process. Here we review recent progress understanding different experimental theoretical aspects physics dynamics transport...
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...
The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order advance spherical torus (ST) concept. In do this, NSTX utilizes up 7.5 MW neutral beam injection, 6 harmonic fast waves (HHFWs), it operates with plasma currents 1.5 MA elongations 2.6 a field 0.45 T. New facility, diagnostic modelling capabilities developed over past two years have enabled research team make significant progress...
Molecular deuterium fluxes into the edge of deuterium-fuelled L-mode discharges are measured using passive visible spectroscopy D2 emission lines. Comparison with atomic influx Dα suggests that a significant fraction plasma fuelling from walls is in form D2. flux observed both divertor and main chamber regions but roughly factor 100 smaller near inner wall 1000 outer wall, when compared region. Very high levels molecular excitation measured, ground state rotational population temperatures...
Abstract Recent experimental evidence suggests the importance of fast radial plasma transport in scrape‐off‐layer (SOL) tokamaks. The outward appears to be convective rather than diffusive, extends into far SOL, and can produce significant recycling from main‐chamber walls, partially bypassing divertor. A plausible theoretical mechanism explain this phenomenon is “blobs” locally dense created by turbulent processes. related process inward “holes” reduced density plasma, which provides a for...
The impact of tungsten dust originating from divertor plates on the performance edge plasma in ITER-like discharge is evaluated using computer modeling with coupled dust-plasma transport code DUSTT-UEDGE. Different injection parameters, including size and mass rates, are surveyed. It found that rates as low a few mg/s can lead to dangerously high impurity concentrations core. Dust injections tens shown have significant effect parameters dynamics ITER scale tokamaks. large certain phenomena,...
Recombination of hydrogen plasma in the divertor volume is a simple explanation for detachment phenomena experimentally observed on many tokamaks and simulators. The presence vibrationally excited molecules detached provides an additional mechanism recombination, so-called molecular assisted recombination (MAR). cross-section data atomic processes relevant conditions are reviewed. Collisional radiative kinetics cascade excitation vibrational electronic states as well dissociation, ionization...
Multi-fluid two-dimensional transport models such as the UEDGE code model [T. D. Rognlien et al., J. Nucl. Mater. 196–198, 34 (1992)] are widely used in simulation of tokamak edge plasmas. Usually these based on assumption anomalous plasma diffusion direction perpendicular to magnetic field lines. As will be shown, pure diffusive cross-field is inadequate and fails match properly parameters measured both scrape-off layer (SOL) divertor DIII-D tokamak. Recently it has been suggested that...
The National Spherical Torus Experiment (NSTX) has made considerable progress in advancing the scientific understanding of high performance long-pulse plasmas needed for future spherical torus (ST) devices and ITER.Plasma durations up to 1.6 s (five current redistribution times) have been achieved at plasma currents 0.7 MA with non-inductive fractions above 65% while simultaneously achieving β T N values 17% 5.7 (%m -1 ), respectively.A newly available motional Stark effect diagnostic...
Two different oscillatory plasma regimes induced by seeding the with high- and low-Z impurities are found for ITER-like divertor plasmas, using computer modeling DUSTT/UEDGE SOLPS4.3 plasma-impurity transport codes. The oscillations characterized significant variations of impurity-radiated power peak heat load on targets. Qualitative analysis reveals mechanisms driving in cases impurity seeding. caused high-Z excited near X-point an impurity-related instability radiation-condensation type,...