A5048368712- Magnetic confinement fusion research
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Nuclear reactor physics and engineering
- Solar and Space Plasma Dynamics
- Semiconductor materials and devices
- Physics of Superconductivity and Magnetism
- Electrostatic Discharge in Electronics
- Atomic and Subatomic Physics Research
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Data Storage Technologies
- Dust and Plasma Wave Phenomena
- Laser-induced spectroscopy and plasma
- Nuclear Physics and Applications
- Silicon Carbide Semiconductor Technologies
- High voltage insulation and dielectric phenomena
- Atomic and Molecular Physics
- Semiconductor Quantum Structures and Devices
- Computational Fluid Dynamics and Aerodynamics
- Particle Detector Development and Performance
- Magnetic Field Sensors Techniques
General Atomics (United States)
2015-2024
Baidu (China)
2019
Oak Ridge National Laboratory
1981-2016
Princeton Plasma Physics Laboratory
1997-2016
University of California, San Diego
2008-2016
École Polytechnique Fédérale de Lausanne
2003-2013
Culham Centre for Fusion Energy
1996-2013
Culham Science Centre
2013
Columbia University
2013
University of California, Irvine
2010
An efficient method is given to reconstruct the current profile parameters, plasma shape, and a consistent with magnetohydrodynamic equilibrium constraint from external magnetic measurements, based on Picard iteration approach which approximately conserves measurements. Computational efforts are reduced by parametrizing linearly in terms of number physical parameters. Results detailed comparative calculations sensitivity study described. Illustrative profiles shapes ohmically auxiliarily...
The predictions of gyrokinetic and gyrofluid simulations ion-temperature-gradient (ITG) instability turbulence in tokamak plasmas as well some plasma thermal transport models, which have been widely used for predicting the performance proposed International Thermonuclear Experimental Reactor (ITER) [Plasma Physics Controlled Nuclear Fusion Research, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 1, p. 3], are compared. These comparisons provide information on effects...
A model based on magnetohydrodynamic (MHD) stability of the tokamak plasma edge region is presented, which describes characteristics localized modes (ELMs) and pedestal. The emphasizes dual role played by large bootstrap currents driven sharp pressure gradients in pedestal region. Pedestal reduce magnetic shear, stabilizing high toroidal mode number (n) ballooning modes, while at same time providing drive for intermediate to low n peeling modes. result that coupled peeling–ballooning...
An efficient method is given for self-consistent reconstruction of the tokamak current profiles and their associated magnetic topology using magnetohydrodynamic (MHD) equilibrium constraint from external measurements, kinetic profile internal poloidal field topological information soft X-ray (SXR) measurements. Illustrative examples beam heated H-mode divertor discharges in DIII-D are presented, experimentally measured data existing diagnostics. Comparative reconstructions various...
Peaked pressure profiles and central ion temperatures up to 20 keV are observed in DIII-D $H$-mode discharges with a region of strongly reversed magnetic shear. Short wavelength ballooning modes stabilized by access the second stable regime, longer conducting wall possibly rotational Values normalized beta, ${\ensuremath{\beta}}_{N}=\frac{\ensuremath{\beta}\mathrm{aB}}{I}$, 4 (%-$m$-T/MA), energy confinement factor 3 better than $L$ mode, at least 50% noninductive plasma current this regime...
The maximum normalized beta achieved in long-pulse tokamak discharges at low collisionality falls significantly below both that observed short pulse and predicted by the ideal MHD theory. Recent experiments, particular those simulating International Thermonuclear Experimental Reactor (ITER) [M. Rosenbluth et al., Plasma Physics Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1995), Vol. 2, p. 517] scenarios with νe*, are often limited low-m/n nonideal...
One modeling framework for integrated tasks (OMFIT) is a comprehensive which has been developed to enable physics codes interact in complicated workflows, and support scientists at all stages of the cycle. The OMFIT development follows unique bottom-up approach, where design capabilities organically evolve progressive integration components that are required accomplish goals increasing complexity. provides workflow easily generating full kinetic equilibrium reconstructions constrained by...
A practical method for performing a tokamak equilibrium reconstruction in real time arbitrary varying discharge shapes and current profiles is described. An approximate solution to the Grad-Shafranov relation found which best fits diagnostic measurements. Thus, spatial distribution of poloidal flux toroidal density available that consistent with plasma force balance, allowing accurate evaluation parameters such as shape safety factor profile. The solutions are produced at rate sufficient...
DIII-D discharges with values of beta (the ratio plasma pressure to magnetic pressure) up 12.5% demonstrate that a resistive wall can stabilize low- $n$ magnetohydrodynamic (MHD) modes. In broad current profiles, exceeds the ideal MHD stability limit by at least factor 1.3 assuming no wall, but remains below calculated under assumptions vacuum vessel is perfectly conducting wall. Plasma rotation essential stabilization, and instabilities resembling predicted ``resistive mode'' appear only...
AbstractAbstractPhysics elements and advances crucial for the development of axisymmetric magnetohydrodynamic equilibrium reconstruction to support plasma operation data analysis in DIII-D tokamak are reviewed. A response function formalism a Picard linearization scheme used efficiently combine fitting iterations search optimum solution vector. Algorithms incorporate internal current pressure profile measurements, topological constraints, toroidal rotation into described. Choice basis...
Integral relations for the average poloidal beta p and plasma internal inductance ℓi are derived from magnetohydrodynamic (MHD) equilibrium equation an axisymmetric torus. The volume-dependent parameters that appear depend only weakly on actual current density distribution inside can be evaluated approximately, given shape boundary magnetic field. In practice, these accurately efficiently obtained both diverted limited plasmas measured external field flux values by approximating using a few...
It is shown that the theoretical predictions and experimental observations of toroidicity-induced Alfvén eigenmodes (TAE’s) are now in good agreement, with particularly detailed agreement mode frequencies. Calculations driving damping rates predict importance continuum for low toroidal numbers this confirmed experimentally. However, calculations finite-β, shaped discharges existence other global modes, particular ellipticity-induced eigenmode (EAE) a new mode, beta-induced (BAE). The BAE...
We review and test the peeling–ballooning model for edge localized modes (ELMs) pedestal constraints, a based upon theoretical analysis of magnetohydrodynamic (MHD) instabilities that can limit height drive ELMs. A highly efficient MHD stability code, ELITE, is used to calculate quantitative constraints on pedestal, including height. Because impact collisionality bootstrap current, these are dependent density temperature separately, rather than simply pressure. ELITE calculations directly...
High-confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced physics. This choice, however, comes at a significant cost both and tokamaks because of effects edge localized modes (ELMs). ELMs can produce erosion in divertor affect beta limit reduced core transport regions needed operation. Experimental results from DIII-D [J. L. Luxon et al., Plasma Physics Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency,...
Following boronization, tokamak discharges in DIII-D have been obtained with confinement times up to a factor of 3.5 above the ITER89-P L-mode scaling and 1.8 greater than DIII-D/JET H-mode relation. Very high phases are characterized by relatively central density ${\mathit{n}}_{\mathit{e}}$(0)\ensuremath{\approxeq}1\ifmmode\times\else\texttimes\fi{}${10}^{20}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$, ion temperatures 13.6 keV at moderate plasma currents (1.6 MA) heating powers (12.5--15.3...
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...
The toroidicity-induced gaps of the shear Alfvén wave spectrum in tokamaks are shown to satisfy an envelope equation. structure these gaps, and location high-n gap modes, which localized modes with frequency gap, studied for general numerically generated equilibria. dependence frequencies on equilibrium properties, such as elongation, triangularity, β plasma explored.
A variational method is developed to find approximate solutions the Grad–Shafranov equation. The surfaces of constant poloidal magnetic flux ψ(R, Z) are obtained by solving a few ordinary differential equations, which moments equation, for Fourier amplitudes inverse mapping R(ψ, ϑ) and Z(ψ, ϑ). Analytic properties moment equations considered. Specific calculations using Impurity Study Experiment (ISX-B) Engineering Test Facility (ETF)/International Tokamak Reactor (INTOR) geometries...
Fusion whole device modeling simulations require comprehensive models that are simultaneously physically accurate, fast, robust, and predictive. In this paper we describe the development of two neural-network (NN) based as a means to perform snon-linear multivariate regression theory-based for core turbulent transport fluxes, pedestal structure. Specifically, find NN-based approach can be used consistently reproduce results TGLF EPED1 over broad range plasma regimes, with computational...
Recent EAST/DIII-D joint experiments on the high poloidal beta tokamak regime in DIII-D have demonstrated fully noninductive operation with an internal transport barrier (ITB) at large minor radius, normalized fusion performance increased by ≥30% relative to earlier work (Politzer et al 2005 Nucl. Fusion 45 417). The advancement was enabled improved understanding of 'relaxation oscillations', previously attributed repetitive ITB collapses, and fast ion behavior this regime. It found that...
Research in NSTX has been conducted to establish spherical torus plasmas be used for high β, auxiliary heated experiments. This device a major radius R0 = 0.86 m and midplane halfwidth of 0.7 m. It operated with toroidal magnetic field B0 ⩽ 0.3 T Ip 1.0 MA. The evolution the plasma equilibrium is analysed between discharges an automated version EFIT code. Limiter, double null lower single diverted configurations have sustained several energy confinement times. stored reached 92 kJ (βt 17.8%)...
H-mode operation is the choice for next-step tokamak devices based either on conventional or advanced physics. This choice, however, comes at a significant cost both and tokamaks because of effects edge-localized modes (ELMs). ELMs can produce erosion in divertor affect β limit reduced core transport regions needed operation. Recent experimental results from DIII-D have demonstrated new operating regime, quiescent which solves these problems. We achieved ELM-free yet has good density...
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...
The motional electric field E=v×B, where v is the velocity and B tokamak magnetic field, produces a strong Stark effect in spectral lines emitted by hydrogenic neutral beams. tilt angle of line, quantity related directly to distribution plasma toroidal current, deduced from measurement direction polarization components. In DIII-D tokamak, Balmer-α line deuterium one high-power heating beams analyzed. A multichord polarimeter measures pitch at eight spatial locations covering ∼0.6 nominal...