A5087937753- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Nuclear Materials and Properties
- Nuclear reactor physics and engineering
- Nuclear Physics and Applications
- Metal and Thin Film Mechanics
- Laser-induced spectroscopy and plasma
- Physics of Superconductivity and Magnetism
- Atomic and Subatomic Physics Research
- Semiconductor materials and devices
- Metallurgical Processes and Thermodynamics
- Atomic and Molecular Physics
- Q Methodology Applications
- Advanced Data Storage Technologies
- Silicon and Solar Cell Technologies
- Solar and Space Plasma Dynamics
- Advanced materials and composites
- Diamond and Carbon-based Materials Research
- Advanced Materials Characterization Techniques
- Semiconductor Quantum Structures and Devices
General Atomics (United States)
2013-2024
University of Tennessee at Knoxville
2002-2018
Lawrence Livermore National Laboratory
1995-2018
Knoxville College
2018
Sandia National Laboratories California
2018
University of California, San Diego
1995-2018
Oak Ridge Associated Universities
2018
Oak Ridge National Laboratory
2018
Oak Ridge Institute for Science and Education
2012
ITER
2010-2011
The paradigm of shear suppression turbulence as the mechanism for low to high confinement mode (L H) transition is examined by quantitative comparison predictions with experimental results from DIII-D tokamak [Plasma Physics and Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1986), p. 159]. L H trigger V×B rotation, not main ion pressure gradient. radial electric field Er increases before fluctuation suppression, consistent increasing cause suppression. spatial...
The hypothesis of stabilization turbulence by shear in the E×B drift speed successfully predicts observed reduction and confinement improvement seen at L (low)–H (high) transition; addition, levels significantly exceed value theoretically required to stabilize turbulence. Furthermore, this same is best explanation date for further plasma core when goes from H mode VH (very high) mode. Consequently, most fundamental question H-mode studies now is: How electric field Er formed? radial force...
Abstract Divertor detachment offers a promising solution to the challenge of plasma-wall interactions for steady-state operation fusion reactors. Here, we demonstrate excellent compatibility actively controlled full divertor with high-performance ( β N ~ 3, H 98 1.5) core plasma, using high-β p (poloidal beta, > 2) scenario characterized by sustained internal transport barrier (ITB) and modest edge (ETB) in DIII-D tokamak. The high- high-confinement facilitates which, turn, promotes...
Edge conditions in DIII-D are being quantified order to provide insight into the physics of H mode regime. Several studies show that electron temperature is not key parameter controls L-H transition. Gradients edge and pressure much more promising candidates for elements such parameters. They systematically increase during L phases discharges which make a transition mode, these increases typically larger than underlying quantities. The quality confinement strongly correlated with height...
Fusion power has been increased by a factor of 3 in DIII-D tailoring the pressure profile to avoid kink instability $H$-mode plasmas. The resulting plasmas are found have neoclassical ion confinement. This reduction transport losses beam-heated with negative central shear is correlated dramatic density fluctuations. Improved magnetohydrodynamic stability achieved controlling plasma width. In deuterium highest gain $Q$ (the ratio fusion input power), was 0.0015, corresponding an equivalent...
Recent QH-mode research on DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1996 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] has used the peeling-ballooning modes model of edge magnetohydrodynamic stability as a working hypothesis to organize data; several predictions this theory are consistent with experimental results. Current ramping results indicate that QH operate near current limit set by peeling modes. This operating point...
A new small angle slot (SAS) divertor concept has been developed to enhance neutral cooling across the target by coupling a closed structure with appropriate shaping. Initial tests on DIII-D find strong interplay between such anticipated 'SAS' effects and cross-field drifts, favouring operation ion B × ∇B drift away from X-point, as currently employed for advanced tokamaks. This offers following key improvements relative DIII-D's open lower or partially-closed upper divertor: (i) SAS allows...
Using resonant magnetic perturbations with toroidal mode number n = 3, we have produced H-mode discharges without edge localized modes (ELMs) which run constant density and radiated power for periods up to about 2550 ms (17 energy confinement times). These ELM suppression results are achieved at pedestal collisionalities close those desired next step burning plasma experiments such as ITER provide a means of eliminating the rapid erosion divertor components in machines could be caused by...
Measurements of the internal magnetic field structure Texas Experimental Tokamak discharges are made by use laser-induced fluorescence an injected ${\mathrm{Li}}^{0}$ beam. From measurements near axis, we obtain axial safety factor, ${q}_{0}$ (or equivalently rotational transform, \ensuremath{\iota}=2\ensuremath{\pi}/q) for various discharge conditions. In particular, low-${q}_{a}$ sawtoothing discharges, find time-averaged values significantly less than 1 (\ensuremath{\sim}0.7 to 0.8), in...
SOLPS-EIRENE edge code analysis shows that a gas-tight slot divertor geometry with small-angle (glancing-incidence) target, named the small angle (SAS) divertor, can achieve cold, dissipative/detached conditions at relatively low values of plasma density outside midplane separatrix. SAS exhibits following key features: (1) strong enhancement buildup neutral in localized region near strike point on target; (2) spreading cooling front across target gradually flaring out from point, thus...
It is important to develop a predictive capability for the tungsten source rate near strike points during H-mode operation in ITER and beyond. deuterium plasma exposures were performed on W-coated graphite molybdenum substrates DIII-D divertor using DiMES. The W-I 400.9 nm spectral line was monitored by fast filtered diagnostics cross calibrated via high-resolution spectrometer resolve inter-ELM W erosion. effective ionization/photon (S/XB) unique method developed based surface analysis....
Abstract A total power injection up to 0.3 GJ has been achieved in EAST long pulse H-mode operation of 101.2 s with an ITER-like water-cooled tungsten (W) mono-block divertor, which steady-state exhaust capability 10 MWm −2 . The peak temperature W target saturated at 12 the value T ~ 500 °C a heat flux ~3.3 MW m being maintained during discharge. By tailoring 3D divertor plasma footprint through edge magnetic topology change, load was broadly dispersed and thus sputtering were well...
Significant progress in obtaining high performance discharges lasting many energy confinement times the DIII-D tokamak has been realized recent experimental campaigns. Normalized ~10 sustained for more than 5τE with qmin>1.5. (The normalized is measured by product βN H89, indicating proximity to conventional β limits and quality, respectively.) These H mode have an ELMing edge 1. The global parameters were chosen optimize potential fully non-inductive current sustainment at performance,...
It is known that the toroidal angular momentum and ion thermal energy are correlated in tokamak discharges heated by neutral beam injection. Here, data from ten years of measurements on DIII-D considered, for representative all types conditions. The ratio simple replacement times found to order this correlation indicating these approximately equal, across minor radius. Representative several discussed more detail, as well transport analysis results diffusivities.
Turbulence is significantly reduced in a tokamak plasma as result of neon seeding an L-mode discharge. Correspondingly, confinement improved and cross-field ion thermal transport reduced. Fully saturated turbulence the range 0.1</=k( perpendicular)rho(s)</=0. 6 measured at rho = 0.7 exhibits factor 5 reduction total power after injection, with almost complete suppression for k( perpendicular)rho(s)>0.35. These observations are consistent calculated linear growth rate perpendicular)rho(s)>0.5...
Localized currents driven by pressure gradients play a pivotal role in the magnetohydrodynamic stability of toroidal plasma confinement devices. We have measured generated edge L- (low) and H- (high confinement) mode discharges on DIII-D tokamak, utilizing Zeeman effect an injected lithium beam to obtain high resolution profiles poloidal magnetic field. find current densities excess 1 MA/m2 2 cm region near peak gradient. These values are sufficient challenge theories based specific formation models.
Scrape-off layer plasma simulation modeling has been carried out to assess the effect of tightly closing lower divertor in DIII-D, which at present is almost fully open, on achievement cold dissipative/detached conditions. To isolate impact other factors solution and make direct comparisons, most parameters including meshes were kept as similar possible. Only neutral baffling was modified compare a open with closed one. The shows that greatly improves trapping recycling neutrals, thereby...
Tungsten nanostructures (W-fuzz) prepared in the PISCES-A linear device have been found to survive direct exposure divertor plasmas DIII-D. W-fuzz was exposed lower of DIII-D using material evaluation system. Two samples were single null (LSN) deuterium H-mode plasmas. The first sample three discharges terminated by vertical displacement event disruptions, and second two near lowered X-point. More recently, outer strike point predominantly helium LSN In all cases, survived plasma with little...
Abstract A set of experiments are planned to exploit the high SOL collisionality enabled by a tightly baffled slot divertor geometry suppress tungsten leakage in DIII-D. toroidal row graphite tiles from Small Angle Slot (SAS) is being coated with 10–15 μ m tungsten. New spectroscopic viewing chords in-vacuo optics will measure W gross erosion source surface spatial and temporal resolution. In parallel, bottom SAS changed flat ‘V’ shape. SOLPS-ITER/DIVIMP simulations conducted drifts using...
Strong impacts of drifts on the divertor plasma in–out asymmetry and detachment are demonstrated in DIII-D with an open configuration. For forward toroidal field, BT, i.e., ion B × ∇B drift toward divertor, particle flux to inner as represented by Langmuir probe measured saturation current (Jsat), exhibits a double peak structure, electron temperature, lower at target. Reversing BT direction reverses both radial poloidal E flows, leading broad profile outboard scrape-off layer (SOL) similar...