A5043263974- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Nuclear reactor physics and engineering
- Particle accelerators and beam dynamics
- Solar and Space Plasma Dynamics
- Atomic and Molecular Physics
- Laser-induced spectroscopy and plasma
- Nuclear Materials and Properties
- Gas Dynamics and Kinetic Theory
- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Fluid Dynamics and Turbulent Flows
- Meteorological Phenomena and Simulations
- Advanced Data Storage Technologies
- Vacuum and Plasma Arcs
- High-pressure geophysics and materials
- Cold Fusion and Nuclear Reactions
- CCD and CMOS Imaging Sensors
- Engineering Applied Research
- Atmospheric and Environmental Gas Dynamics
- Spacecraft and Cryogenic Technologies
Princeton Plasma Physics Laboratory
2012-2022
Princeton University
2007-2020
Lawrence Livermore National Laboratory
2001-2017
Lodestar Research Corporation (United States)
2017
Oak Ridge National Laboratory
1997-2016
Johns Hopkins University
2001-2016
University of Wisconsin–Madison
1997-2016
National Agency for New Technologies, Energy and Sustainable Economic Development
2016
University of Padua
2016
Auburn University
2016
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.
The two-dimensional (2D) radial vs poloidal structure of edge turbulence in the Alcator C-Mod tokamak [I. H. Hutchinson, R. Boivin, P. T. Bonoli et al., Nucl. Fusion 41, 1391 (2001)] was measured using fast cameras and compared with three-dimensional numerical simulations plasma turbulence. main diagnostic is gas puff imaging, which visible Dα emission from a localized D2 viewed along local magnetic field line. observed fluctuations have typical scale ≈1 cm, often strong maxima (“blobs”)...
The intermittent turbulent transport in the scrape-off-layer (SOL) of Alcator C-Mod [I.H. Hutchinson, R. Boivin, P.T. Bonoli et al., Nucl. Fusion 41, 1391 (2001)] is studied experimentally by imaging with a very high density spatial measurements. two-dimensional structure and dynamics emission from localized gas puff are observed, features (also sometimes called “filaments” or “blobs”) typically seen. characteristics turbulence their relationship to time-averaged SOL profiles discussed...
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...
Abstract We are currently rewriting the neutral gas transport code, DEGAS [1, 2], with a view to not only making it faster, but also easing process of including new physics. The goal is make adding species and reactions relatively simple so that code can be rapidly adapted divertor physics regimes. 2 will optimized for coupling fluid plasma codes, incorporating many techniques utilized in B2‐EIRENE[3–5]. Finally, our intention 2, like DEGAS, well‐documented easy use. present model...
Because experiment/model comparisons in magnetic confinement fusion have not yet satisfied the requirements for validation as understood broadly, a set of approaches to validating mathematical models and numerical algorithms are recommended good practices. Previously identified procedures, such verification, qualification, analysis error uncertainty, remain important. However, particular challenges intrinsic plasmas physical measurement therein lead identification new or less familiar...
Liquid metal plasma-facing components (PFCs) have been proposed as a means of solving several problems facing the creation economically viable fusion power reactors. To date, few demonstrations exist this approach in diverted tokamak and we here provide an overview such work on National Spherical Torus Experiment (NSTX). The Lithium Divertor (LLD) was installed operated for 2010 run campaign using evaporated coatings filling method. LLD consisted copper-backed structure with porous...
Gas puff imaging (GPI) is a diagnostic of plasma turbulence which uses neutral gas at the edge to increase local visible light emission for improved space-time resolution fluctuations. This paper reviews diagnostics in magnetic fusion research, with focus on instrumentation, cross-checks, and interpretation issues. The hardware, optics, detectors are described about 10 GPI systems implemented over past ∼15 years. Comparison results other described, many common features observed. Several...
Here, the structure and motion of discrete plasma blobs (a.k.a. filaments) in edge scrape-off layer NSTX is studied for representative Ohmic H-mode discharges. Individual were tracked 2D radial versus poloidal plane using data from gas puff imaging diagnostic taken at 400 000 frames s-1. A database blob amplitude, size, ellipticity, tilt, velocity was obtained ~45 individual blobs. Empirical relationships between various properties are described, e.g. speed amplitude tilt ellipticity. The...
The gas puff imaging (GPI) diagnostic can be used to study the turbulence present at edge of magnetically confined plasmas. In this instantaneous two-dimensional (2D) radial vs poloidal structure is measured using fast-gated cameras and discrete fast chords. By a controlled neutral puff, typically helium or deuterium, brightness contrast turbulent emission fluctuations are increased independently natural recycling. addition, recent advances in ultrafast framing allow followed time. itself...
This paper describes the first observations in National Spherical Torus Experiment (NSTX) [S. M. Kaye et al., Phys. Plasmas 8, 1977 (2001)] of “quiet periods” edge turbulence preceding low-to-high (L-H) mode transition, as diagnosed by gas puff imaging (GPI) diagnostic near outer midplane separatrix. During these quiet periods GPI Dα light emission pattern was transiently similar to that seen during H-mode, i.e., with a relatively small fraction located outside These had frequency ∼3 kHz for...
This paper describes the range of variations in edge and SOL turbulence observed using a gas puff imaging (GPI) diagnostic NSTX discharges. The database consists 140 shots including Ohmic, L-mode, H-mode plasmas measured during steady-state conditions (e.g. without ELMs). Turbulence quantities were evaluated both cross-correlation analysis blob tracking. Relative fluctuation levels varied from –1.0, correlation times –40 μs, lengths –10 cm, velocities km s−1 outwards. These with respect to...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation J. R. Myra, D. A. Russell, D'Ippolito, J.-W. Ahn, Maingi, Maqueda, P. Lundberg, Stotler, S. Zweben, Boedo, M. Umansky, NSTX Team; Reduced model simulations of the scrape-off-layer heat-flux width comparison with experiment. Phys. Plasmas 1 January 2011; 18 (1): 012305. https://doi.org/10.1063/1.3526676 Download...
In this paper we compare the structure and motion of edge turbulence observed in L-mode vs. H-mode plasmas National Spherical Torus Experiment (NSTX) [M. Ono, M. G. Bell, R. E. Bell et al., Plasma Phys. Controlled Fusion 45, A335 (2003)]. The radial poloidal correlation lengths are not significantly different between cases examined. velocity fluctuations lower profiles somewhat flatter compared with plasmas. These results similar measurements Alcator C-Mod [E. Marmar, B. Bai, L. Boivin Nucl....
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...
This paper describes quantitative comparisons between turbulence measured in the scrape-off layer (SOL) of Alcator C-Mod [S. Scott, A. Bader, M. Bakhtiari et al., Nucl. Fusion 47, S598 (2007)] and three dimensional computations using electromagnetic gyrofluid equations a two-dimensional tokamak geometry. These were made for outer midplane SOL set inner-wall limited, near-circular Ohmic plasmas. The B field plasma density varied to assess gyroradius collisionality scaling. poloidal radial...
Use of a large-area liquid lithium limiter in the CDX-U tokamak produced largest relative increase (an enhancement factor 5–10) Ohmic confinement ever observed. The results from do not agree with existing scaling laws, and cannot easily be projected to new experiment (LTX). Numerical simulations low recycling discharges have now been performed ASTRA-ESC code special reference transport model suitable for diffusion-based regime, incorporating boundary conditions nonrecycling walls, fuelling...
While intermittent filamentary structures, also known as blobs, are routinely seen in the low-field-side scrape-off layer of National Spherical Torus Experiment (NSTX) (Ono et al 2000 Nucl. Fusion 40 557 ), fine structured filaments on lower divertor target plates NSTX. These filaments, not associated with edge localized modes, correspond to interaction turbulent blobs near midplane plasma facing components. The fluctuation level neutral lithium light observed at divertor, and skewness...
Atomic and molecular density data in the outer midplane of NSTX [Ono et al., Nucl. Fusion 40, 557 (2000)] are inferred from tangential camera via a forward modeling procedure using DEGAS 2 Monte Carlo neutral transport code. The observed Balmer-β light emission 17 shots during 2010 campaign display no obvious trends with discharge parameters such as divertor Balmer-α level or edge deuterium ion density. Simulations 12 time slices 7 these discharges produce densities near vacuum vessel wall...
A synthetic gas puff imaging (GPI) diagnostic has been added to the scrape-off layer turbulence (SOLT) simulation code, enabling comparisons with GPI data from National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)]. The edge and are modeled in radial poloidal (bidirectional) dimensions of outboard midplane region NSTX. low-confinement mode discharge is simulated by choosing reference parameters, including density temperature profiles, be consistent those shot...
The effects of recycled neutral atoms on tokamak ion temperature gradient (ITG) driven turbulence have been investigated in a steep edge pedestal, magnetic separatrix configuration, with the full-f gryokinetic code XGC1. An adiabatic electron model has used; hence, impacts particles and density are not considered, nor electromagnetic effects. enhance ITG turbulence, first, by increasing pedestal via cooling charge exchange and, second, relative reduction shearing rate.
Abstract Lithium-coated high- Z substrates are planned for use in the NSTX-U divertor and a candidate plasma facing component (PFC) reactors, but it remains necessary to characterize gross Li erosion rate under high fluxes (>10 23 m −2 s −1 ), typical region. In this work, realistic model compositional evolution of Li/D layer is developed that incorporates first principles molecular dynamics (MD) simulations D diffusion liquid Li. Predictions from mixed material also include formation...
Monte Carlo neutral transport simulations of hydrogen velocities in the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)] are compared with experiment using Doppler-broadened Balmer-α spectral line profile. Good agreement is obtained under a range conditions, validating treatment charge exchange, molecular dissociation, surface reflection, and sputtering gas code DEGAS [D. Heifetz J. Comput. 46, 309 (1982)]. A residual deficiency 10–100 eV neutrals most...