A5107833937- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Fusion materials and technologies
- Solar and Space Plasma Dynamics
- Particle accelerators and beam dynamics
- Nuclear reactor physics and engineering
- Laser-induced spectroscopy and plasma
- Nuclear Physics and Applications
- Fluid Dynamics and Turbulent Flows
- Silicon Carbide Semiconductor Technologies
- Physics of Superconductivity and Magnetism
- Advanced Data Storage Technologies
- Electrostatic Discharge in Electronics
- Meteorological Phenomena and Simulations
- Semiconductor materials and devices
- Quantum Chromodynamics and Particle Interactions
- Dust and Plasma Wave Phenomena
- Advancements in Semiconductor Devices and Circuit Design
- Theoretical and Computational Physics
- Quantum and electron transport phenomena
- Semiconductor Quantum Structures and Devices
- Gas Dynamics and Kinetic Theory
The University of Texas at Austin
2015-2024
Fusion (United States)
2011-2023
Fusion Academy
2001-2023
Lawrence Livermore National Laboratory
2019
Princeton University
2019
Princeton Plasma Physics Laboratory
2019
United States Department of Energy
1989-1996
Max Planck Institute for Plasma Physics
1990-1992
Max Planck Society
1988-1990
General Atomics (United States)
1989
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.
The TEXT/(TEXT-U) tokamak, formerly built and operated by the University of Texas at Austin in USA, was dismantled shipped to China 2004, renamed as Joint TEXT (J-TEXT) tokamak. reconstruction work, which included reassembly machine development peripheral devices, completed spring 2007. Consequently, first plasma obtained end At present, a typical J-TEXT ohmic discharge can produce with flattop current up 220 kA lasting for 300 ms, line-averaged density above 2 × 10 19 m −3 , an electron...
This article reviews digital spectral analysis techniques that yield experimental insight into plasma turbulence. Methods to quantify the statistical properties of fluctuations and measure particle heat flux caused by electrostatic are presented. Furthermore, study nonlinear coupling process turbulence redistribution energy among different modes discussed. The impact on fusion research is demonstrated with results collected Langmuir probes, heavy-ion beam laser scattering in tokamak TEXT....
Abstract Recent J-TEXT research has highlighted the significance of role that non-axisymmetric magnetic perturbations, so called three-dimensional (3D) perturbation (MP) fields, play in a fundamentally 2D concept, i.e. tokamaks. This paper presents results achieved over last two years, especially on impacts 3D MP fields magnetohydrodynamic instabilities, plasma disruptions and turbulence transport. On J-TEXT, resonant (RMP) system, capable providing either static or high frequency (up to 8...
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...
The unsaturated linear rise of the energy confinement time with density, ${\ensuremath{\tau}}_{E}\ensuremath{\sim}{\overline{n}}_{e}$, up to density limit is recovered in Ohmically heated discharges ASDEX. Improvement a factor 2 reached ${\ensuremath{\tau}}_{E}\ensuremath{\approx}150$ ms at ${\overline{n}}_{e}=5\ifmmode\times\else\texttimes\fi{}{10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ improved state characterized by peaked profiles. ion heat diffusivity decreases neoclassical value....
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...
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,...
The Texas Experimental Tokamak is a medium-scale tokamak operated as national user facility. Now in operation, it provides plasma with 1-m major radius, 28-cm minor and 400-kA nominal current at up to 3-T toroidal field for pulse lengths of 300 500 ms. facility includes all standard diagnostics an integrated data system that makes available after each shot, often once every 2 min. design generally conventional conservative; the vacuum vessel numerous large-aperture radial vertical ports...
Recent theories have shown that the instability driven by a cold, weak electron beam in one-dimensional plasma is stabilized when unstable wave grows to an amplitude sufficient trap beam. Quantitative measurements of confirm every prediction theory: maximum amplitude, monochromaticity mode, harmonic content and wavelength slow oscillation amplitude. The goes through same patterns phase space time-averaged f(v) as predicted. Both scaling absolute magnitudes agree with theory.
Abstract In the last two years, three major technical improvements have been made on J-TEXT in supporting of expanded operation regions and diagnostic capabilities. (1) The successful commission 105 GHz/500 kW/1 s electron cyclotron resonance heating (ECRH) system increasing core temperature from 0.9 keV up to around 1.5 keV. (2) poloidal divertor configuration with an X -point high-field side has achieved. particular, 400 kW wave also successfully injected into diverted plasma. (3) A...
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,...
By modulating the small gas feed required to maintain a steady-state Tokamak discharge density perturbation may be induced from whose propagation particle transport parameters adduced. Experiments in TEXT show that phenomena adequately described by simple model with constant diffusion plus inward convection except near limit. Diffusion coefficients and convective velocities has been determined for broad range of hydrogen discharges found scale approximately as (nq)-1. The results are...
The transport coefficients for particles and heat will certainly depend upon plasma parameters. Besides making the equilibrium equations nonlinear, this introduces a multitude of new terms in set linearized equations, which can be used to describe effects perturbations system. A general such is obtained that includes most physical dependences coefficients. If driven by gradients density or temperature, as would expected from turbulence theories, significant quantitative result. Perturbations...
The shape and amplitude of the electron-plasma wave spectrum resulting from a "gentle bump" on tail electron velocity distribution plasma is measured found to be in good agreement with quasilinear theory.
Abstract The J-TEXT capability is enhanced compared to two years ago with several upgrades of its diagnostics and the increase electron cyclotron resonance heating (ECRH) power 1 MW. With application wave (ECW), ECW assisted plasma startup achieved; tearing mode suppressed; toroidal injection 300 kW drives around 24 kA current; fast electrons are generated injected runaway current conversion efficiency increases ECRH power. coupling between 2/1 3/1 modes extensively studied. coupled usually...
Recent DIII-D experiments have significantly improved the understanding of internal transport barriers (ITBs) that are triggered close to time when an integer value minimum in q is crossed. While this phenomenon has been observed on many tokamaks, extensive and fluctuation diagnostics permitted a detailed study generation mechanisms q-triggered ITBs as pertaining turbulence suppression dynamics, shear flows, energetic particle modes. In these discharges, evolution profile measured using...
Particle transport coefficients have been obtained for a wide range of conditions and confinement regimes in ASDEX by analysis the density perturbations induced modulation gas feed. The data are sufficiently precise to distinguish diffusion convective velocity central outer parts plasma. A strong inward velocity, especially part plasma, is found all cases. region often be closely related with energy confinement. Diffusion lower deuterium than hydrogen decreases strongly at densities which...
The nonlinear evolution of the instability resulting from a gentle bump on tail electron velocity distribution plasma was investigated experimentally. An beam with large spread injected along axis collisionless column immersed in strong magnetic field. equilibrium wave amplitude, spectral shape, and were measured found to be good agreement predictions quasilinear theory, providing met requirements theory. When too bump, deviations theory appeared.
An overview of the recent research work on J-TEXT tokamak over last two years is presented. A series experiments and simulations interaction between resonant magnetic perturbations (RMPs) plasma were carried out tokamak. The results show that m/n = 2/1 (m n are poloidal toroidal mode numbers, respectively) locking obtained with sufficiently large RMPs. And suppression tearing by moderate perturbation amplitude also observed. With experimental parameters as input, both RMPs simulated...
The experimental research over last two years on the J-TEXT tokamak is summarized and presented in paper. high-performance polarimeter-interferometer developed J-TEXT, aiming to measure electron density Faraday angle simultaneously, has time response up 1 µs, phase resolution <0.1° spatial ~3 cm. Such high permits investigations of fast equilibrium dynamics as well magnetic perturbations associated with magnetohydrodynamic instabilities. Particle transport due sawtooth crashes analysed....
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 nonlinear limit of the instability driven by a low density cold electron beam in collisionless plasma is experimentally found to be determined trapping most rapidly growing wave.
Nonlinear Landau damping, the nonlinear interaction between two waves in which beat disturbance is resonant with particle thermal velocities, has been observed for electron plasma waves. The results confirm predictions of weak-turbulence theory.
In this paper, we introduce the first direct perturbed particle transport measurements in resonant magnetic perturbation (RMP) H-mode plasmas. The increases as a result of application RMP deep into core. core, large reduction E × B shear to value below linear growth rate, conjunction with increasing density fluctuations, is consistent an increase turbulent transport. edge, changes are less obvious. There clear correlation between rates and fluctuations measured at different scales, but it...