A5007934502- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Nuclear reactor physics and engineering
- Spacecraft and Cryogenic Technologies
- Nuclear Materials and Properties
- Nuclear Physics and Applications
- Electromagnetic Launch and Propulsion Technology
- Physics of Superconductivity and Magnetism
- Fluid Dynamics and Turbulent Flows
- Particle Accelerators and Free-Electron Lasers
- Aerodynamics and Fluid Dynamics Research
- Magnetic Field Sensors Techniques
- Semiconductor materials and devices
- Quantum chaos and dynamical systems
- Gas Dynamics and Kinetic Theory
- Metal and Thin Film Mechanics
- Advancements in Semiconductor Devices and Circuit Design
- Astro and Planetary Science
- Atomic and Subatomic Physics Research
Oak Ridge National Laboratory
2015-2024
Energy Center of Wisconsin
2024
Princeton Plasma Physics Laboratory
2008-2016
University of Colorado Boulder
2016
Max Planck Society
2014
Max Planck Institute for Plasma Physics
2014
University of Evansville
2013
Lawrence Livermore National Laboratory
2011-2012
Columbia University
2011
University of California, San Diego
2009
The SPARC tokamak is a critical next step towards commercial fusion energy. designed as high-field ( $B_0 = 12.2$ T), compact $R_0 1.85$ m, $a 0.57$ m), superconducting, D-T with the goal of producing gain $Q>2$ from magnetically confined plasma for first time. Currently under design, will continue path Alcator series tokamaks, utilizing new magnets based on rare earth barium copper oxide high-temperature superconductors to achieve high performance in device. achievable conservative...
Deoxyribonucleic acid (DNA) sequence analysis of the control region mitochondrial DNA (mtDNA) genome was used to identify human skeletal remains returned United States government by Vietnamese in 1984. The postmortem interval thought be 24 years at time testing, and presumed an American service member. typing methods using nuclear genomic DNA, HLA-DQ alpha variable number tandem repeat (VNTR) locus D1S80, were unsuccessful polymerase chain reaction (PCR). Amplification a portion mtDNA...
The Super-X Divertor (SXD), a robust axisymmetric redesign of the divertor magnetic geometry that can allow fivefold increase in core power density toroidal fusion devices, is presented. With small changes poloidal coils and currents for standard divertors, SXD allows largest plate radius inside field coils. This increases plasma-wetted area by 2–3 times over all flux-expansion-only methods (e.g., near main X point, tilting, divertor, snowflake), decreases parallel heat flux hence plasma...
Abstract The spherical tokamak (ST) is a leading candidate for Fusion Nuclear Science Facility (FNSF) due to its compact size and modular configuration. National Spherical Torus eXperiment (NSTX) MA-class ST facility in the US actively developing physics basis an ST-based FNSF. In plasma transport research, experiments exhibit strong (nearly inverse) scaling of normalized confinement with collisionality, if this trend holds at low high fusion neutron fluences could be achievable very...
Abstract A fusion nuclear science facility (FNSF) could play an important role in the development of energy by providing environment needed to develop materials and components. The spherical torus/tokamak (ST) is a leading candidate for FNSF due its potentially high neutron wall loading modular configuration. key consideration choice configuration range achievable missions as function device size. Possible include: fluence, demonstrating tritium self-sufficiency, electrical self-sufficiency....
Abstract Lithium wall coatings have been shown to reduce recycling, suppress edge-localized modes (ELMs), and improve energy confinement in the National Spherical Torus Experiment (NSTX). Here we document effect of gradually increasing lithium on discharge characteristics, with reference ELMy discharges obtained boronized, i.e. non-lithiated conditions. We observed a continuous but not quite monotonic reduction recycling improvement confinement, gradual alteration edge plasma profiles,...
Experiments in the National Spherical Torus Experiment (NSTX) have shown beneficial effects on performance of divertor plasmas as a result applying lithium coatings graphite and carbon-fiber-composite plasma-facing components. These mostly been applied by pair evaporators mounted at top vacuum vessel which inject collimated streams vapor toward lower divertor. In neutral beam injection (NBI)-heated deuterium H-mode run immediately after application lithium, modifications included decreases...
With fusion device performance hinging on the edge pedestal pressure, it is imperative to experimentally understand physical mechanism dictating characteristics and validate improve predictive models. This Letter reports direct evidence of density magnetic fluctuations showing stiff onset an instability leading saturation Alcator C-Mod tokamak. Edge stability analyses indicate that unstable both ballooning mode kinetic in agreement with observations.
Lithium wall coatings have been shown to reduce recycling, improve energy confinement, and suppress edge localized modes in the National Spherical Torus Experiment. Here, we show that these effects depend continuously on amount of predischarge lithium evaporation. We observed a nearly monotonic reduction decrease electron transport, modification profiles stability with increasing lithium. These correlations challenge basic expectations, given even smallest exceeded needed for nominal...
Direct measurements of the pedestal recovery during an edge-localized mode cycle provide evidence that quasi-coherent fluctuations (QCFs) play a role in inter-ELM dynamics. Using fast Thomson scattering measurements, density and temperature evolutions are probed on sub-millisecond time scales to show gradient compared gradient. The appears drive for onset (as measured with magnetic probe diagnostics) localized pedestal. amplitude evolution these QCFs tracks including its saturation. Such...
Owing to its high magnetic field, power, and compact size, the SPARC experiment will operate with divertor conditions at or above those expected in reactor-class tokamaks. Power exhaust this scale remains one of key challenges for practical fusion energy. Based on empirical scalings, peak unmitigated parallel heat flux is projected be greater than 10 GW m −2 . This nearly an order magnitude higher has been demonstrated date. Furthermore, Edge-Localized Mode (ELM) energy fluence projections...
Abstract In this paper, we present linear and nonlinear gyrokinetic analyses in the pedestal region of two DIII-D ELMy H-mode discharges using CGYRO code. The otherwise matched employ different divertor configurations to investigate impact varying recycling particle source on profiles. Linear simulations find electrostatic ion-scale instabilities (ion temperature gradient trapped electron modes, ITG–TEM) are just inside top with growth rates that enhanced significantly by parallel velocity...
Abstract Physics-based simulations project a compact net electric fusion pilot plant with nuclear testing mission is possible at modest scale based on the advanced tokamak concept, and identify key parameters for its optimization. These utilize new integrated 1.5D core-edge approach whole device modeling to predict performance by self-consistently applying transport, pedestal current drive models converge fully non-inductive stationary solutions, predicting profiles energy confinement given...
Differences in the electron particle and thermal transport are reported between plasmas produced a quasihelically symmetric (QHS) magnetic field configuration with symmetry broken. The diffusivity is reduced QHS configuration, resulting higher temperatures than nonsymmetric for fixed power input. density profile centrally peaked, core hollow. hollow due to neoclassical thermodiffusion, which configuration.
An H-mode edge pedestal plasma transport benchmarking exercise was undertaken for a single DIII-D pedestal. Transport modelling codes used include 1.5D interpretive (ONETWO, GTEDGE), predictive (ASTRA) and 2D ones (SOLPS, UEDGE). The particular discharge considered is 98889, which has typical low density Profiles the are obtained from Thomson charge-exchange recombination data averaged over last 20% of average 33.53 ms repetition time between type I localized modes. modelled recycled...
We report on a recent set of experiments performed in NSTX to explore the effects non-axisymmetric magnetic perturbations stability edge-localized modes (ELMs). The application these 3D fields was found have strong effect ELM stability, including destabilization ELMs H-modes otherwise free large ELMs. Exploiting perturbations, been controllably introduced into lithium-enhanced ELM-free H-modes, causing reduction impurity accumulation while maintaining high confinement. Although show...
The application of nonaxisymmetric magnetic fields is shown to destabilize edge-localized modes (ELMs) during otherwise ELM-free periods discharges in the National Spherical Torus Experiment (NSTX). Profile analysis shows applied increased temperature and pressure gradients, decreasing edge stability. This robust effect was exploited for a new form ELM control: triggering ELMs at will high performance H mode plasmas enabled by lithium conditioning, yielding time-averaged energy confinement...
Joint experiment/theory/modelling research has led to increased confidence in predictions of the pedestal height ITER. This work was performed as part a US Department Energy Research Target FY11 identify physics processes that control H-mode structure. The study included experiments on C-Mod, DIII-D and NSTX well interpretation experimental data with theory-based modelling codes. provides ability models for peeling–ballooning stability, bootstrap current, width scaling make correct...
The coating of plasma facing components (PFCs) with lithium improves energy confinement and eliminates ELMs in the National Spherical Torus Experiment, latter due to a relaxation density pressure profiles that reduces drive for peeling-ballooning modes. 2-D interpretive transport modeling discharges without shows reduction PFC recycling coefficient from R ∼ 0.98 0.90 is required match drop Dα emission coatings. A broadening edge barrier region showing reduced coefficients observed, ∼75% D χe...
The pedestal structure in NSTX is strongly affected by lithium coatings applied to the PFCs. In discharges with lithium, density widens, and electron temperature (Te) gradient increases inside a radius of ψN ∼ 0.95, but unchanged for > 0.95. inferred effective thermal particle profiles reflect profile changes: slightly increased near-separatrix region, reduced region < 0.95 with-lithium case. shows broadening low diffusivity while minimum value within steep-gradient comparable two cases....
Research on the National Spherical Torus Experiment, NSTX, targets physics understanding needed for extrapolation to a steady-state ST Fusion Nuclear Science Facility, pilot plant, or DEMO. The unique operational space is leveraged test theories next-step tokamak operation, including ITER. Present research also examines implications coming device upgrade, NSTX-U. An energy confinement time, τE, scaling unified varied wall conditions exhibits strong improvement of BTτE with decreased electron...
The National Spherical Torus Experiment (NSTX) has undergone a major upgrade, and the NSTX Upgrade (NSTX-U) Project was completed in summer of 2015.NSTX-U first plasma subsequently achieved, diagnostic control systems have been commissioned, H-mode accessed, magnetic error fields identified mitigated, physics research campaign carried out.During ten run weeks operation, NSTX-U surpassed record pulse-durations toroidal (TF), high-performance ~1 MA plasmas comparable to best sustained near...
Linear plasma generators are cost effective facilities to simulate divertor conditions of present and future fusion reactors. They used address important R&D gaps in the science material interactions towards viable facing components for Next generation have be able access expected on targets ITER devices. The steady-state linear device MPEX will this regime with electron temperatures 1–10 eV densities . resulting heat fluxes about 10 MW is designed deliver those a novel Radio Frequency...
We report the first successful use of lithium (Li) to eliminate edge-localized modes (ELMs) with tungsten divertor plasma-facing components in EAST device. Li powder injected into scrape-off layer upper successfully eliminated ELMs for 3–5 s EAST. The ELM elimination became progressively more effective consecutive discharges at constant delivery rates, and Dα baseline emission was reduced, both signatures improved wall conditioning. A modest decrease stored energy normalized confinement also...
Transport characteristics and predicted confinement are shown for the Infinity Two fusion pilot plant baseline plasma physics design, a high field stellarator concept developed using modern optimization techniques. predictions made fidelity nonlinear gyrokinetic turbulence simulations along with drift kinetic neoclassical simulations. A pellet fueled scenario is proposed that enables supporting an edge density gradient to substantially reduce ion temperature turbulence. Trapped electron mode...