A5025079368- Magnetic confinement fusion research
- Superconducting Materials and Applications
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Advanced Data Storage Technologies
- Laser-Plasma Interactions and Diagnostics
- Semiconductor materials and devices
- Nuclear reactor physics and engineering
- Electrostatic Discharge in Electronics
- Radiation Effects in Electronics
- Particle Detector Development and Performance
- Iterative Learning Control Systems
- Computational Fluid Dynamics and Aerodynamics
- Nuclear Physics and Applications
- Advancements in Semiconductor Devices and Circuit Design
- Silicon Carbide Semiconductor Technologies
- Model Reduction and Neural Networks
- Target Tracking and Data Fusion in Sensor Networks
- Power System Optimization and Stability
- Granular flow and fluidized beds
- Gas Dynamics and Kinetic Theory
- Stability and Controllability of Differential Equations
- High voltage insulation and dielectric phenomena
General Atomics (United States)
2013-2022
University College Cork
2012
Oak Ridge National Laboratory
2009
Lehigh University
2008
Lawrence Livermore National Laboratory
2007
University of California, Los Angeles
1984-2004
École Polytechnique Fédérale de Lausanne
2003
University of Rochester
1977-1991
Office of Scientific and Technical Information
1989
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...
Significant progress has been made in the area of advanced modes operation that are candidates for achieving steady state conditions a fusion reactor. The corresponding parameters, domain operation, scenarios and integration issues discussed this chapter. A review presently developed scenarios, including discussions on operational space, is given. heating current drive recent years, especially off-axis drive, which essential achievement required profile. actuators necessary to produce...
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...
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...
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...
Sustained stabilization of the n=1 kink mode by plasma rotation at beta approaching twice stability limit calculated without a wall has been achieved in DIII-D combination error field reduction and sufficient drive. Previous experiments have transiently exceeded no-wall limit. However, demonstration sustained rotational remained elusive because found to decay whenever is stabilized. Recent theory [Boozer, Phys. Rev. Lett. 86, 5059 (2001)] predicts resonant response fields marginal low-n...
Abstract Physics-based simulations project a compact net electric fusion pilot plant with nuclear testing mission is possible at modest scale based on the advanced tokamak concept, and identify key parameters for its optimization. These utilize new integrated 1.5D core-edge approach whole device modeling to predict performance by self-consistently applying transport, pedestal current drive models converge fully non-inductive stationary solutions, predicting profiles energy confinement given...
In a magnetic fusion reactor, the achievement of certain type plasma current profiles, which are compatible with magnetohydrodynamic stability at high pressure, is key to enable gain and non-inductive sustainment for steady-state operation. The approach taken toward establishing such profiles DIII-D tokamak create desired profile during ramp-up early flattop phases. evolution in time related poloidal flux, modeled normalized cylindrical coordinates using partial differential equation usually...
Recent high-β DIII-D (Luxon J.L. 2002 Nucl. Fusion 42 64 ) experiments with the new capability of balanced neutral beam injection show that resistive wall mode (RWM) remains stable when plasma rotation is lowered to a fraction per cent Alfvén frequency by reducing angular momentum in discharges minimized magnetic field errors. Previous yielded high threshold (of order few frequency) for RWM stabilization resonant braking was applied lower rotation. We propose previously observed can be...
The requirements of the DIII-D physics program have led to development many operational control results with direct relevance ITER. These include new algorithms for robust and sustained stabilization neoclassical tearing modes electron cyclotron current drive, model-based controllers resistive wall mode in presence ELMs, coupled linear–nonlinear provide good dynamic axisymmetric while avoiding coil limits, adaptation plasma system (PCS) operate next-generation superconducting tokamaks....
In tokamak fusion plasmas, control of the spatial distribution profile toroidal plasma current plays an important role in realizing certain advanced operating scenarios. These scenarios, characterized by improved confinement, magnetohydrodynamic stability, and a high fraction non-inductively driven current, could enable steady-state reactor operation with gain. Current experiments at DIII-D focus on using combination feedforward feedback to achieve targeted during ramp-up early flat-top...
Research on the National Spherical Torus Experiment, NSTX, targets physics understanding needed for extrapolation to a steady-state ST Fusion Nuclear Science Facility, pilot plant, or DEMO. The unique operational space is leveraged test theories next-step tokamak operation, including ITER. Present research also examines implications coming device upgrade, NSTX-U. An energy confinement time, τE, scaling unified varied wall conditions exhibits strong improvement of BTτE with decreased electron...
Systematic experimental and modeling investigations on DIII-D show attractive transport properties of fully non-inductive high βp plasmas. Experiments that the large-radius internal barrier (ITB), a key feature providing excellent confinement in regime, is maintained when scenario extended from q95 ∼ 12 to 7 rapid near-zero toroidal rotation. The robustness versus rotation was predicted by gyrofluid showing dominant neoclassical ion energy even without E × B shear effect. physics mechanism...
Detailed analysis of recent high beta discharges in the DIII-D [Plasma Physics Controlled Nuclear Fusion Research, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] tokamak demonstrates that resistive vacuum vessel can provide stabilization low n magnetohydrodynamic (MHD) modes. The experimental values reaching up to βT=12.6% are more than 30% larger maximum stable calculated with no wall stabilization. Plasma rotation is essential for When plasma slows sufficiently,...
A pedestal database was built using data from type-I ELMy H-modes of ASDEX Upgrade, DIII-D and JET. ELM synchronized were analysed with the two-line method. The method is a bilinear fit which shows better reproducibility parameters than modified hyperbolic tangent fit. This tested simulated experimental data. influence equilibrium reconstruction on investigated sophisticated reconstructions CLISTE EFIT including edge kinetic profiles. No systematic deviation between codes could be observed....
We review progress made on the advanced tokamak path to fusion energy by DIII-D National Fusion Facility (Luxon et al. in Nucl 42:614, 2002). The represents a highly attractive approach for future steady state power plant. In this concept, there is natural alignment between high pressure operation, favorable stability and transport properties, self-driven ('bootstrap') plasma current sustain operation efficiently without disruptions. Research has identified several promising configurations...
The amplitude and frequency of modes driven in the edge region tokamak high mode (H-mode) discharges [type I edge-localized (ELMs)] are shown to depend on discharge shape. measured pressure gradient threshold for instability its scaling with shape compared predictions from ideal magnetohydrodynamic theory low toroidal number (n) instabilities by current density good agreement is found. Reductions observed shapes either squareness or triangularity where stability predicted be reduced most...
The dependence of edge stability on plasma shape and local pressure gradients P' in the DIII-D JT-60U tokamaks is studied. stronger shaping allows region discharges with type I (giant) ELMs to have access second for ideal ballooning modes a larger pedestal gradient than ELM discharges. These are near mode first regime limit. results support an based working model as low intermediate toroidal number, n, MHD modes. from analysis indicate that predictions this also consistent observations.
Experiments on the stabilization of highly elongated, vertically unstable plasmas were carried out DIII-D tokamak. Identification closed-loop transfer function showed that vertical stability could be usefully modelled as a second order dynamical system. The effect varying controller gains and field decay index was studied found to qualitatively predicted by low model proposed previously. implementation new hybrid inboard/outboard coil positional control with differing dynamics allowed...
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...
Plasma shape control using real-time equilibrium reconstruction has been implemented on the National Spherical Torus Experiment.The rtEFIT code originally developed for use DIII-D was adapted NSTX.The equilibria provide calculations of flux at points plasma boundary, which is used as input to a algorithm known isoflux control.The desired boundary location compared reference value, and this error basic feedback quantity poloidal 1 field coils hardware that comprises system described, well...
Recent studies on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] have elucidated key aspects of dependence stability, confinement, and density control plasma magnetic configuration, leading to demonstration nearly noninductive operation for >1 s with pressure 30% above ideal no-wall stability limit. Achieving fully requires high pressure, good through divertor pumping. Plasma geometry affects all these. Ideal magnetohydrodynamics modeling external kink suggests that it...
Setting up a suitable current spatial profile in tokamak plasmas has been demonstrated to be key condition for one possible advanced scenario with improved confinement and steady-state operation. Experiments at the DIII-D focus on creating desired during plasma ramp-up early flattop phases aim of maintaining this target subsequent discharge. The evolution time is related poloidal magnetic flux, which modeled normalized cylindrical coordinates using parabolic partial differential equation...
The achievement of suitable toroidal-current-density profiles in tokamak plasmas plays an important role enabling high fusion gain and noninductive sustainment the plasma current for steady-state operation with improved magnetohydrodynamic stability. evolution time profile is related to poloidal magnetic flux, which modeled normalized cylindrical coordinates using a partial differential equation (PDE) usually referred as flux diffusion equation. dynamics density can be modified by total...