A5040239271- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Superconducting Materials and Applications
- Quantum chaos and dynamical systems
- Plasma Diagnostics and Applications
- Dust and Plasma Wave Phenomena
- Nuclear reactor physics and engineering
- Physics of Superconductivity and Magnetism
- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Laser-induced spectroscopy and plasma
- Astro and Planetary Science
- Quantum, superfluid, helium dynamics
- Nuclear physics research studies
- Fluid Dynamics and Turbulent Flows
- Atomic and Molecular Physics
- Theoretical and Computational Physics
- Geomagnetism and Paleomagnetism Studies
- Cold Atom Physics and Bose-Einstein Condensates
- High-pressure geophysics and materials
- Nonlinear Dynamics and Pattern Formation
Princeton Plasma Physics Laboratory
2015-2024
Princeton University
2015-2024
National Institute for Fusion Science
2022
National Institutes for Quantum Science and Technology
2021
University of Georgia
2021
The University of Texas at Austin
1983-2019
Fusion (United States)
1983-2019
Fusion Academy
1981-2019
University of Maryland, College Park
2018
Saint Michael's College
2018
Three-dimensional gyrokinetic simulations of microturbulence in magnetically confined toroidal plasmas with massively parallel computers showed that, linear flow damping, an asymptotic residual develops agreement analytic calculations. Nonlinear global instabilities driven by temperature gradients the ion component plasma support view that turbulence-driven fluctuating zonal flows can substantially reduce turbulent transport. Finally, outstanding differences dynamics observed and local are...
Energetic trapped particles are shown to have a destabilizing effect on the internal kink mode in tokamaks. The growth rate is near ideal magnetohydrodynamic value, but frequency comparable trapped-particle precession frequency. A model for instability cycle gives stability properties, associated particle losses, and neutron emissivity consistent with "fishbone" events observed poloidal divertor experiments.
A Hamiltonian guiding center drift orbit formalism is developed which permits the efficient calculation of particle trajectories in magnetic field configurations arbitrary cross section with plasma β. The assumed to be a small perturbation from zero-order ‘‘equilibrium’’ possessing surfaces. equilibrium field, helical or toroidal symmetry, can modeled analytically obtained numerically codes. used study trapped precession. Finite banana width corrections precession rate are derived, and...
Raman and Brillouin scattering of an electromagnetic wave in inhomogeneous, expanding plasma are studied. Application to laser-pellet irradiation is considered.
Strong magnetohydrodynamic activity has been observed in PDX neutral-beam-heated discharges. It occurs for ${\ensuremath{\beta}}_{T}q>~0.045$ and is associated with a significant loss of fast ions drop neutron emission. As much as 20%-40% the beam heating power may be lost. The instability repetitive bursts oscillations \ensuremath{\le} 1 msec duration at 1-6-msec intervals. dubbed "fishbone instability" from its characteristic signature on Mirnov coils.
A quasi-linear analytical model is used to describe the nonlinear growth and saturation of tearing modes with mode number m⩾2. The magnetic island development a single rather than coupling process. amplitude, which dependent on form resistivity, in good agreement results obtained previously by numerically advancing full set equations.
An analytical dispersion relation is derived which shows that, in toroidal plasmas, zonal flows can be spontaneously excited via modulations the radial envelope of a single-n coherent drift wave, with n mode number. Predicted instability features are verified by three-dimensional global gyrokinetic simulations ion-temperature-gradient mode. Nonlinear equations for amplitudes demonstrate saturation linearly unstable pump wave and nonlinear oscillations drift-wave intensity flows,...
The banana orbits of high-energy trapped particles in tokamaks are found to diffuse rapidly the radial direction if toroidal ripple exceeds a low critical value. During this diffusion energy, magnetic moment, and value field strength at tips conserved.
A probabilistic method for the solution of Vlasov equation has been applied to Chirikov-Taylor model. The analytical solutions probability function and its second velocity moment have obtained. Good agreement between theory numerical computations found.
As part of the ITER Design Review and in response to issues identified by Science Technology Advisory Committee, physics requirements were reviewed as appropriate updated. The focus this paper will be on recent work affecting design with special emphasis topics near-term procurement arrangements. This describe results on: sensitivity studies, poloidal field coil requirements, vertical stability, effect toroidal ripple thermal confinement, material choice heat load for plasma-facing...
A compact path-diagram method has been introduced for the calculation of velocity moments a probability function. This is complementary to approach developed earlier by Rechester and White. It applied Chirikov-Taylor model. Analytic expressions velocity-space diffusion have derived compared with numerical computations. path summations which more efficient than directly advancing model equations, applicable small field-amplitude values, where direct stepping impractical.
The spatial variation of the amplitude electromagnetic radiation propagating into an inhomogeneous plasma is discussed in reference to nonlinear interaction HCN laser with plasmas and experiments on r.f. heating ionosphere. Previous results ordinary wave extraordinary at normal incidence are reviewed emphasis physical processes affecting behaviour. New numerical obtained starting from integral representation solution equation for waves a cold, inhomogeneous, magnetized slab. Resonance...
Large-amplitude rotating magnetohydrodynamic modes are observed to induce significant high-energy beam particle loss during high-power perpendicular netural injection on the poloidal divertor experiment (PDX). A Hamiltonian formalism for drift orbit trajectories in presence of such is used study induced analytically and numerically. Results good agreement with experiment.
The Sweet–Parker and Petschek scalings of the magnetic reconnection rate are modified to include effect viscosity. show that viscous can be important in high-β plasmas. theoretical compared with numerical simulation results a tokamak geometry for three different cases: forced driven by external coils, nonlinear m=1 resistive internal kink, m=2 tearing mode. In first two cases, agrees well scaling when viscosity is sufficiently large. When negligible, steady state which was assumed derivation...
We solve exactly the temporal evolution and spatial dependence of a three-wave parametric instability in an inhomogeneous plasma. An initial fluctuation develops into pulse grows initially with same growth rate as it would homogeneous Growth continues until convection saturation occurs. The broadens eventually assumes form totally amplified region flanked by two shock fronts. Effects damping are also discussed.
A set of numerical techniques for investigating the full nonlinear unstable behavior low-β kink modes given helical symmetry in tokamaks is presented. Uniform current density plasmas display complicated deformations including formation large vacuum bubbles provided that safety factor q sufficiently close to integral. Fairly m=1 deformations, but not bubble formation, persist a plasma with parabolic profile (and hence shear). Deformations m⩾2 are, however, greatly suppressed.
Experiments in the DIII-D tokamak show that fast-ion transport suddenly becomes stiff above a critical threshold presence of many overlapping small-amplitude Alfv\'en eigenmodes (AEs). The is phase-space dependent and occurs when particle orbits become stochastic due to resonances with AEs. Above threshold, equilibrium density profiles are unchanged despite increased drive, intermittent losses observed. Fast-ion $\mathrm{D}\ensuremath{\alpha}$ spectroscopy indicates radially localized...
Super-thermal ions and electrons occur in both space fusion plasmas. Because these energetic particles (EP) have large velocities, EP orbits necessarily deviate substantially from magnetic surfaces. Orbits are described by conserved constants of motion that define topological boundaries for different orbit types. Electric field perturbations produced instabilities can disrupt particle orbits, causing the to change. The statistics “kicks” associated with determines resulting cross transport....
Compact optimized stellarators offer novel solutions for confining high-β plasmas and developing magnetic confinement fusion. The three-dimensional plasma shape can be designed to enhance the magnetohydrodynamic (MHD) stability without feedback or nearby conducting structures provide drift-orbit similar tokamaks. These configurations possibility of combining steady-state low-recirculating power, external control, disruption resilience previous with low aspect ratio, high β limit, good...
Physics knowledge (theory and experiment) in energetic particles relevant to design of a reactor scale tokamak is reviewed, projections for ITER are provided this Chapter the Basis. The review includes single particle effects such as classical alpha heating toroidal field ripple loss, well collective instabilities that might be generated plasmas by particles. overall conclusion fusion expected provide an efficient plasma ignition sustained burn next step device. major concern localized heat...
Fusion-born α particles moving parallel to the magnetic field can resonate with toroidal Alfvén eigenmodes (TAE) leading anomalous α-orbit diffusion across α-loss boundaries in a tokamak. This is analyzed using Hamiltonian guiding center code orbit conjunction kinetic magnetohydrodynamics (MHD) eigenmode solving nova-k. Resonant single orbits are studied below and above threshold for stochasticity Monte Carlo randomized ensembles of alphas subjected finite amplitude time-dependent TAE...
Resonant heating of particles by electrostatic and Alfvén waves propagating in a confining uniform magnetic field is examined. It shown that, with sufficiently large wave amplitude, significant perpendicular stochastic can be obtained frequency at fraction the cyclotron frequency. This result may have relevance for ions solar corona, generic phenomenon, independent type considered.
A three-dimensional (3-D) hybrid gyrokinetic-MHD (magnetohydrodynamic) simulation scheme is presented. To the 3-D toroidal MHD code, MH3D-K energetic particle component added as gyrokinetic particles. The resulting mh3d-k, used to study nonlinear behavior of effects in tokamaks, such stabilization sawteeth, fishbone oscillations, and alpha-particle-driven Alfvén eigenmode (TAE) modes.