A5076025100- Magnetic confinement fusion research
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Atomic and Molecular Physics
- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Plasma Diagnostics and Applications
- Nuclear Physics and Applications
- Mass Spectrometry Techniques and Applications
- Nuclear reactor physics and engineering
- Solar and Space Plasma Dynamics
- Atomic and Subatomic Physics Research
- Fluid Dynamics and Turbulent Flows
- X-ray Spectroscopy and Fluorescence Analysis
- Metal and Thin Film Mechanics
- Gyrotron and Vacuum Electronics Research
- Particle Accelerators and Free-Electron Lasers
- Dust and Plasma Wave Phenomena
- Semiconductor materials and devices
- Physics of Superconductivity and Magnetism
- Electromagnetic Launch and Propulsion Technology
- Scientific Measurement and Uncertainty Evaluation
- Meteorological Phenomena and Simulations
Fusion Academy
2011-2024
Fusion (United States)
2015-2024
The University of Texas at Austin
2015-2024
Institute of Plasma Physics
2018
Chinese Academy of Sciences
2018
Lawrence Livermore National Laboratory
2018
Korea Institute of Fusion Energy
2018
Hefei University of Technology
2018
Princeton Plasma Physics Laboratory
2015-2016
Plasma Technology (United States)
1999-2016
Regimes of high-confinement mode have been studied in the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994)]. with no edge localized modes (ELM-free) compared detail to a new regime, enhanced Dα (EDA). EDA discharges only slightly lower energy confinement than comparable ELM-free ones, but show markedly reduced impurity confinement. Thus do not accumulate impurities and typically fraction radiated power. The gradients seem be relaxed by continuous process rather an...
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.
It now appears feasible to deposit positrons (e+) in a tokamak plasma by injecting bursts of neutral positronium atoms (e+e−), which are then ionized the plasma. The annihilation time these is long compared with typical particle containment times. Thus subsequent transport can be studied monitoring dependence annihilation, gamma radiation produced when strike limiter. This paper discusses design such an experiment, kinds data obtained, and physics questions this experiment might address....
The object of this review is to summarize the achievements research on Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994) and Marmar, Fusion Sci. Technol. 51, 261 (2007)] place that in context quest for practical fusion energy. a compact, high-field tokamak, whose unique design operating parameters have produced wealth new important results since it began operation 1993, contributing data extends tests critical physical models into parameter ranges regimes. Using only...
A finite but small injection of carbon into the TEXT tokamak edge induces significant temperature perturbations throughout plasma. Large, rapid decreases are observed in outer third, while temperatures inner third promptly begin to rise. The effects cannot be reproduced with transport coefficients that functions only local thermodynamic variables. large increase ${\ensuremath{\chi}}_{e}$ must occur within 100 \ensuremath{\mu}s region, and simultaneously decrease interior. Increases density...
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...
In general, the sequences of radiofrequency and magnetic field gradients used to form nuclear resonance images are designed for a stationary object. Consequently, these produce different response when applied moving blood. These changes in signal permit visualization vessels can be measure their open area. addition, specific relaxation time signatures lesions may help identifying nature obstructions.
Particle transport in an ohmically heated tokamak plasma was investigated the Texas Experimental Tokamak (TEXT). Spectroscopic measurements of electron source were used with density to derive particle confinement times from continuity equation. Scalings developed for time density, current, toroidal field, and positioning. Simultaneous measurement electrostatic fluctuations Langmuir probes may suggest a correlation between edge TEXT turbulence. In addition, two major features isolated. First,...
We report extended studies of the I-mode regime [Whyte et al., Nucl. Fusion 50, 105005 (2010)] obtained in Alcator C-Mod tokamak [Marmar Sci. Technol. 51(3), 3261 (2007)]. This regime, usually accessed with unfavorable ion B × ∇B drift, features an edge thermal transport barrier without a strong particle barrier. Steady I-modes have now been favorable by using specific plasma shapes, as well drift over wider range shapes and parameters. With power thresholds are close to standard scaling for...
The MIT Plasma Science and Fusion Center collaborators are proposing a high-performance Advanced Divertor RF tokamak eXperiment (ADX)-a specifically designed to address critical gaps in the world fusion research programme on pathway next-step devices: nuclear science facility (FNSF), pilot plant (FPP) and/or demonstration power (DEMO). This high-field (>= 6.5 T, 1.5 MA), high density (P/S similar MW m(-2)) will test innovative divertor ideas, including an 'X-point target divertor' concept,...
The response of a tokamak discharge to sharp drop in edge temperature differs significantly from that expected typical local transport models several important respects. Laser ablation carbon induces large (ΔT/T≤70%), rapid (<200 μs) electron drops the outermost region plasma, r/a≥0.9. This cold pulse proceeds through outer plasma (r/a≥0.75), rapidly compared with power balance or sawtooth predictions. However, shrinks markedly thereafter, disappearing near r/a∼0.5. Within r/a∼0.3,...
New measurements have been made for wavelengths of the 3s–3p, 3p–3d, and 3d–4f transitions sodiumlike ions Cu18+, Zn19+, Ga20+, Ge21+, As22+, Se23+, Br24+, Kr25+, Y28+, Zr29+, Nb30+, Mo31+, Ru33+, Rh34+, Pd35+, Ag36+, Sn39+. The were by photographing laser-produced plasmas tokamak with grazing-incidence spectrographs. energies also calculated Dirac–Fock computer codes. By fitting differences between observed wave numbers to simple formulas, least-squares-fitted all from Ar7+ Xe43+...
Factor of ∼2 higher power thresholds for low- to high-confinement mode transitions (L-H) with unfavorable x-point topologies in Alcator C-Mod [Phys. Plasmas 1, 1511 (1994)] are linked flow boundary conditions imposed by the scrape-off layer (SOL). Ballooning-like transport drives along magnetic field lines from high-field regions toroidal direction dependent on upper/lower balance; rotation confined plasma responds, exhibiting a strong counter-current when B×∇B points away x point. Increased...
Parametric dependences of the heat flux footprint on outer divertor target plate are explored in EDA H-mode and ohmic L-mode plasmas over a wide range parameters with attached plasma conditions.Heat profile shapes found to be independent toroidal field strength, power flow along magnetic lines insensitive x-point topology (single-null versus double-null).The magnitudes widths closely follow that "upstream" pressure profile, which correlated thermal energy content current.Heat decay lengths...
Several seemingly unrelated effects in Alcator C-Mod ohmic L-mode plasmas are shown to be closely connected: non-local heat transport, core toroidal rotation reversals, energy confinement saturation and up/down impurity density asymmetries. These phenomena all abruptly transform at a critical value of the collisionality. At low densities linear regime, with collisionality ?*???0.35 (evaluated inside q?=?3/2 surface), transport exhibits behaviour, is directed co-current, edge profiles...
An overview of the diagnostics installed on Alcator C-Mod tokamak is presented. Approximately 25 diagnostic systems are being operated C-Mod. The compact design machine and cryostat enclosing vacuum vessel magnetic field coils make access challenging. Diagnostics used to study four focus areas: transport, plasma boundary, waves, macrostability. There significant overlap between these topics, they all contribute toward burning advanced thrusts. Several novel investigation plasmas, e.g.,...
Spectra of highly ionized Er, Yb, Hf, W, and Pt were observed by injecting these elements into the plasma TEXT tokamak. Resonance lines 4d10–4d94f transition array in Pd i isoelectronic sequence identified comparison with plots observed-minus-calculated energies. These based on data previously known through Ho21+. They fitted to low-order polynomials that permitted accurate predictions wavelengths Bi37+. In addition, resonance Zn-like Er38+ Hf42+ observed.
Externally applied resonant magnetic fields have been used on TEXT to modify the particle flux and radial electric field near plasma edge. Magnetic with primary mode numbers m/n = 7/3 7/2, an average amplitude ⟨|br|/Bϕ⟩ ≃ 0.1% employed. This perturbation produces mixed islands stochastic regions at edge (r/a ≥ 0.8) without affecting interior. Working transport is shown be increased by typically 30% only in presence of (computed) islands. The effect diminished high perturbing strength when...
Electrostatic drift wave linear stability analysis is carried out for the Helimak configuration and compared against experimental data. Density fluctuation cross-spectrum measurements show evidence of a coherent mode propagating perpendicular to magnetic field which becomes unstable at k⊥ρs∼0.15. By comparing results with characteristic two-fluid theory, this identified as an resistive driven by density gradient grad-B/curvature present in otherwise magnetohydrodynamic stable steady-state...
The sequence of radiofrequency and magnetic field gradients used to form an NMR image produces changes in the signals emitted by moving blood when compared from stationary blood. These can be measure open area vessels. In addition, specific relaxation time signatures lesions may help identifying nature obstructions.
Links between turbulent fluctuations and transport processes in tokamaks, particularly TEXT, are discussed. In the plasma edge probes allow detailed measurements of quantities required to directly determine fluctuation driven fluxes. The total flux particles is well explained by measured electrostatic flux. However, a satisfactory model explain origin has not been identified. responsible for determining electron heat less clear. confinement region experimental observations restricted density...
Global and local transport experiments in ohmic, L-mode H-mode regimes on the Alcator C-Mod tokamak are summarized. For ohmic plasmas, earlier results derived for energy confinement scaling (linear) regime have been confirmed, saturated has shown to be equivalent that of L-mode. auxiliary heated regimes, provided a unique laboratory test standard laws had previously derived. C-Mod's performance matches quite well, but times were about 50% above existing laws. This difference was significant...
Spectra of highly ionized Er, Yb, Hf, W, Pt, and Au were observed with the TEXT tokamak at University Texas Austin. These metals injected into plasma by laser ablation thin-film targets. photographed a 2.2-m grazing-incidence spectrograph in range 40–300 Å. Three strong doublets Ag i isoelectronic sequence identified: 4d104f–4d94f(1P)4f2D, 2F 2G. Interpolated extrapolated wavelengths this derived from plots difference between calculated values for transition energies. The correspondence W...
Experimental results on the Texas Tokamak (TEXT) [Nucl. Technol./Fusion 1, 479 (1982)] and Advanced Toroidal Facility (ATF) torsatron [Fusion Technol. 10, 179 (1986)] indicate that electrostatic fluctuations can explain edge transport of particles perhaps energy. Certain mechanisms for drive (radiation ionization, as well density temperature gradients) stabilization (velocity shear) are suggested by these results. The experimental fluctuation levels turbulence characteristics be reproduced...