A5033583500- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Quantum chaos and dynamical systems
- Plasma Diagnostics and Applications
- Geomagnetism and Paleomagnetism Studies
- Astronomical Observations and Instrumentation
- Atomic and Subatomic Physics Research
- Nuclear reactor physics and engineering
- Astro and Planetary Science
- Atomic and Molecular Physics
- Astronomy and Astrophysical Research
- Physics of Superconductivity and Magnetism
- Laser-induced spectroscopy and plasma
- Quantum, superfluid, helium dynamics
- Theoretical and Computational Physics
- Stellar, planetary, and galactic studies
- Dust and Plasma Wave Phenomena
- Characterization and Applications of Magnetic Nanoparticles
- Advanced Thermodynamics and Statistical Mechanics
- Spacecraft and Cryogenic Technologies
Columbia University
2015-2024
Princeton Plasma Physics Laboratory
1985-2017
University of Wisconsin–Madison
2017
Auburn University
2017
University of Maryland, College Park
2016
Princeton University
1981-2012
Oak Ridge National Laboratory
2011
Massachusetts Institute of Technology
2011
École Polytechnique Fédérale de Lausanne
2000-2011
Fusion Academy
2011
Progress in the area of MHD stability and disruptions, since publication 1999 ITER Physics Basis document (1999 Nucl. Fusion 39 2137–2664), is reviewed. Recent theoretical experimental research has made important advances both understanding control tokamak plasmas. Sawteeth are anticipated baseline ELMy H-mode scenario, but tools exist to avoid or them through localized current drive fast ion generation. Active other instabilities will most likely be also required ITER. Extrapolation from...
Preferential heating of electrons traveling in one direction can support a current even the absence dc electric field. An immediate implication is that waves which carry little toriodal momentum, such as electron cyclotron waves, may be attractive means for generating steady-state toroidal tokamak. analytical expression derived generated per power dissipated, agrees remarkably well with numerical calculations.
The self-consistent classical plasma equilibrium with diffusion is studied in a toroidal geometry having sheared magnetic field. Near each rational surface it found that the pressure gradient zero unless Fourier component of 1/B2, which resonates surface, vanishes. Despite resonances, overall confinement is, practice, only slightly modified by surfaces.
A method is developed for evaluating transport coefficients in asymmetric geometries using the Monte Carlo method. The applied to stellarator.
The equations for particle drift orbits are given in a new magnetic coordinate system. This form of the separates fast motion along field lines from slow across lines. In addition, less information is required about structure than alternative forms equations.
The physics of magnetically confined plasmas has had much its development as part the program to develop fusion energy and is an important element in study space astrophysical plasmas. Closely related areas include Hamiltonian dynamics, kinetic theory, fluid turbulence. A number topics have been developed primarily through research on that underlies magnetic confinement reviewed here make it more accessible those beginning plasma for interested physicists.
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.
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...
Toroidal rotation is normally very weakly damped in plasmas that are magnetically confined the nominally toroidally symmetric tokamak. However, a strong damping of toroidal observed as such approach marginal stability for perturbations produce kinklike distortion plasma. It shown by small departures magnetic field from symmetry greatly enhanced approached. The response plasma to studied using set electrical circuit elements, which provide an equation rotational requires minimal information about
A nominally axisymmetric plasma configuration, such as a tokamak or spherical torus, is highly sensitive to nonaxisymmetric magnetic perturbations due currents outside of the plasma. The high sensitivity means that primary interest in response very small perturbations, i.e., ∣b⃗∕B⃗∣≈10−2 10−4, which can be calculated using theory perturbed equilibria. ideal equilibrium code (IPEC) described and applied study torus external perturbations.
A method is given for expressing the magnetic field strength in coordinates an arbitrary toroidal, scalar pressure, equilibrium with surfaces. The central to study of equilibrium, stability, and transport asymmetric plasmas. While doing these calculations, it assumed that plasma known.
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.
A method of analyzing ergodic magnetic fields is given, including a generalization coordinates to such fields. The results this analysis can be used in existing Monte Carlo codes assess the enhanced transport associated with imperfect surfaces. Hamiltonian for general field given as part analysis.
It is shown that large classes of plasma equilibria can have identical drift orbits and associated transport. Such are called isomorphic. In particular, the neoclassical coefficients given for all in which magnetic field strength depends on one helicity.
The magnetic fields associated with plasmas frequently exhibit small-amplitude MHD fluctuations. It is useful to have equations for the field averaged over these fluctuations, so-called mean equations. Under very general assumptions, it shown that effect of fluctuations on a force-free plasma can be represented by one parameter in Ohm's law, which effectively coefficient electric current viscosity.
A class of model stellarator fields has been found in which the transport is reduced by an order magnitude from conventional stellarators, localizing helical ripple to inside torus. The reduction observed numerical experiments, and explained theoretically. Realizations this are achievable with use modular coils.
Theoretical guidance is needed on two disruption questions: (1) When a tokamak operating in metastable state which loss of control credible (avoidance question)? (2) What the worst level destructive effects when plasma lost and how can these be mitigated (effects The success ITER future tokamaks as fusion systems depend precision with questions answered. Existing capabilities are far from those desired. Nevertheless, one give physical constraints answers scientific issues that must addressed...
Abstract Resilient divertor features connected to open chaotic edge structures in the Helically Symmetric eXperiment are investigated. For first time, an expanded vessel wall was considered that would give space for implementation of a physical target structure. The analysis done four different magnetic configurations with very plasma edges. A resilient interaction pattern identified across all configurations. This manifests as qualitatively similar footprint behavior equilibria. Overall,...
A general circuit formulation of resistive wall mode (RWM) feedback stabilization developed by Boozer [Phys. Plasmas 5, 3350 (1998)] has been used as the basis for VALEN computer code that calculates performance an active control system in arbitrary geometry. The uses a finite element representation thin shell structure integral to model conducting walls. This is combined with stable and unstable plasma modes. Benchmark comparisons results large aspect ratio analytic current driven kink are...
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...
Quasihelically symmetric stellarators are nonaxisymmetric, toroidal configurations in which the strength of magnetic field depends on only one angular coordinate, instead two, within constant pressure surfaces. The confinement properties these similar to those axisymmetric tokamaks. Although with exact quasihelical symmetry proven not exist, good approximations can be found.
The sensitivity of tokamak plasmas to very small deviations from the axisymmetry magnetic field |deltaB/B| approximately 10{-4} is well known. What was not understood until recently importance perturbation plasma equilibrium in assessing effects externally produced asymmetries field, even far a stability limit. DIII-D and NSTX experiments find that when deleterious are mitigated, external asymmetric often made stronger had an increased interaction with unperturbed equilibrium. This Letter...
Small nonaxisymmetric perturbations of the magnetic field can greatly change performance tokamaks through nonambipolar transport. A number theories have been developed, but predictions were not consistent with experimental observations in tokamaks. This Letter provides a resolution, generalized analytic treatment It is shown that discrepancy between theory and experiment be reduced by two effects: (1) small fraction trapped particles for which bounce precession rates resonate; (2) variation...
A method for evaluating transport in nonsymmetric systems is developed and applied to a previously little studied ripple collisionality regime of tokamaks. This regime, the plateau, primary importance both present day reactor scale The results can be directly related like toroidal Z pinch.
The plasma current in ITER cannot be allowed to transfer from thermal relativistic electron carriers. potential for damage is too great. Before the final design chosen mitigation system prevent such a transfer, it important that parameters control physics understood. Equations determine these and their characteristic values are derived. benefits of injection impurities with highest possible atomic number Z slowing cooling during halo ≳40 ms discussed. increases poloidal flux consumption...