A5067906757- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Superconducting Materials and Applications
- Quantum chaos and dynamical systems
- Solar and Space Plasma Dynamics
- Atomic and Molecular Physics
- Astro and Planetary Science
- Advanced Thermodynamic Systems and Engines
- Nuclear reactor physics and engineering
- Dust and Plasma Wave Phenomena
- Geomagnetism and Paleomagnetism Studies
- Spacecraft and Cryogenic Technologies
- Atomic and Subatomic Physics Research
- Gyrotron and Vacuum Electronics Research
- Scientific Research and Discoveries
- Mathematical Dynamics and Fractals
- Chaos control and synchronization
- Nuclear Physics and Applications
- Water Quality Monitoring Technologies
- High-pressure geophysics and materials
- Particle Detector Development and Performance
- Advanced X-ray Imaging Techniques
Auburn University
2015-2024
University of Wisconsin–Madison
2016
University Hospital of Zurich
2016
University of Zurich
2016
University of Maryland, College Park
1980-2005
Naval Surface Warfare Center
1989
The University of Texas at Austin
1984-1985
Fusion Academy
1984-1985
Fusion (United States)
1984-1985
Argonne National Laboratory
1981
A relationship between the Lyapunov numbers of a map with strange attractor and dimension has recently been conjectured. Here, conjecture is numerically tested use several different maps, one which results from system ordinary differential equations occurring in plasma physics. For cases tested, verified to within obtained accuracy.
Systematics of the atomic properties named in title and other related quantities have been comprehensively studied. Our calculations are based on a single-electron approximation using Hartree-Slater central potential---a model that represents reasonable compromise between two goals, namely, realistic description major features dynamics an economical computation necessary for survey over many atoms. results not only quantify general trends as qualitatively expected from periodic table, but...
We report the results of simulations that explain many properties ultracold neutral plasmas. find three-body recombination is important at very low temperatures since it a heating mechanism for electron gas and preferentially removes slow ions from plasma. also collisions between cold electrons Rydberg atoms are an source deexcitation formed in Simulations show Coulomb coupling constant does not become larger than $\ensuremath{\sim}1/5$ reported experiments.
The details of recent calculations the expansion ultra-cold, neutral plasmas are given. performed at several levels. simplest level assumes an ansatz for form electron and ion density; result is a simple, ordinary differential equation which can be easily solved. medium sophistication electrons in thermal equilibrium but does not assume particular partial solved numerically. For highest sophistication, Monte Carlo technique used to solve phase space distribution motion resulting mean field....
The V3FIT code for performing equilibrium reconstruction in three-dimensional plasmas is described. It a modular that has the potential to be coupled with variety of solvers compute externally measured response an arbitrary internal state plasma. Singular-value decomposition used identify dominant components plasma can accurately determined by process and guide minimization χ 2 variance-normalized mismatch between computed signals. Comparison tokamak axisymmetric EFIT presented. reconstruct...
A method for finding integrable Hamiltonian systems with one and a half degrees of freedom is introduced applied to the problem vacuum magnetic fields rotational transform dense set toroidal flux surfaces. In this method, fixed points return map must be located, values corresponding residues calculated. The residues, being indicators stochasticity, are systematically reduced by variation parameters system. Application shows that it practical, yields substantial improvement configuration....
A method for optimizing stellarator vacuum magnetic fields is introduced. Application of this shows that the stochasticity can be made negligible by proper choice coil configuration. This optimization shown to increase equilibrium β limit factors two or more over simple, ‘‘straight’’ winding law. general and ought applicable other systems in which (1) presents a problem, yet (2) affected design parameters.
Compact and computationally efficient expressions for the Biot–Savart magnetic field vector potential of a single filamentary segment are derived. The singular only on segment.
The quantum kicked rotator, the classical limit of which is described by standard map, considered. Particular attention devoted to a study effect finite wavelength on detailed structure phase space appears in limit. In case, for large values nonlinearity parameter, most trajectories are ergodic. However, addition these ergodic trajectories, there can be small integrable regions space, known as accelerator modes, dominate long-time evolution expected value particle energy. this paper it shown...
Using a classical Monte Carlo method, we have computed the three-body recombination (two free electrons and proton scattering into one electron hydrogen atom: $e+e+\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{H}+e)$ in strong magnetic fields. The is allowed its full motion whereas of given by guiding center approximation. We investigate for temperatures fields similar to those used recent experiments that generated anti-hydrogen. When has same temperature as electrons, rate more elaborate...
The Compact Toroidal Hybrid (CTH) is a low-aspect-ratio (), low-beta (%) torsatron with major radius of . CTH operable as pure stellarator, but most research on this device conducted hybrid discharges in which toroidal plasma current driven order to study magnetohydrodynamic instabilities and disruptions current-carrying stellarator plasmas. vacuum helical field produced by continuously wound coil poloidal periodicities , respectively. maximum on-axis toroid al magnetic encloses circular...
Low-aspect-ratio stellarator configurations can be realized by using torsatron windings. Plasmas with aspect ratios in the range of 3.5 to 5 confined these low-aspect-ratio configurations. Stable operation at high beta should possible devices if a vertical field coil system is adequately designed avoid breaking magnetic surfaces finite beta.
The problem of whether or not steady fast kinematic dynamos exist for typical smooth velocity fields has remained an open question in the origin magnetic nature (e.g., observed stars and galaxies). [Here by a flow it is meant that fluid v depends on position x but independent time t, i.e., v=v(x).] Recently been conjectured are produced flows satisfy certain condition. Flows satisfying this condition called D flows. In paper shown how to construct class flows, properties investigated....
In stellarator-type magnetic confinement devices (of which the torsatron is one), field produced entirely by external, current-carrying coils. Two methods for mapping surfaces in Auburn were tested and compared, both of involve use highly transparent screens. The first method consists coating screen with a phosphor that emits light when struck electrons emitted an electron gun. A pattern representative surface formed on screen, this recorded photographically. second uses uncoated to collect...
Axisymmetric equilibrium reconstruction using magnetohydrodynamic solutions to the Grad?Shafranov equation has long been an important tool for interpreting tokamak experiments. This paper describes recent results in non-axisymmetric (three-dimensional) of nominally axisymmetric plasmas (tokamaks and reversed field pinches (RFPs)), fully (stellarators). Results from applying V3FIT code CTH HSX stellarator plasmas, RFX-mod RFP DIII-D are presented.
Low edge safety factor operation at a value less than two (q(a)=1/ι̷tot(a)<2) is routine on the Compact Toroidal Hybrid device with addition of sufficient external rotational transform. Presently, operational space this current carrying stellarator extends down to q(a)=1.2 without significant n = 1 kink mode activity after initial plasma rise phase discharge. The disruption dynamics these low plasmas depend upon fraction helical field transform from coils that generated by current. We...
The virtual-casing principle is used in plasma physics to convert a Biot–Savart integration over current distribution into surface integral that encloses the current. In many circumstances, use of virtual casing can significantly speed up computation magnetic fields. this paper, derived for general vector field with arbitrary divergence and curl. This form thus applicable both magnetostatic fields electrostatic result then related Helmholtz's theorem.
The passive stability of vertically elongated current-carrying toroidal plasmas has been investigated in the Compact Toroidal Hybrid, a stellarator/tokamak hybrid device. In this experiment, fractional transform f, defined as ratio imposed external rotational from stellarator coils to total transform, was varied 0.04 0.50, and elongation κ 1.4 2.2. Plasmas that were unstable evidenced by motion plasma vertical direction. Vertical drifts are measured with set poloidal field pickup coils. A...
The bootstrap current for three electron cyclotron resonance heated plasma scenarios in a quasihelically symmetric stellarator (the Helically Symmetric Experiment) are analyzed and compared to neoclassical transport code PENTA. conditions correspond 50 kW input power with that is off-axis, on-axis heating 100 heating. When the location was moved from off-axis power, stored energy extrapolated steady-state were both observed increase. increased kW, continued increase while slightly decreased....
In order to characterize the Madison Symmetric Torus (MST) reversed-field pinch (RFP) plasmas that bifurcate a helical equilibrium, V3FIT equilibrium reconstruction code was modified include conducting boundary. RFP become at high plasma current, which induces large eddy currents in MST's thick aluminum shell. The boundary accounts for contribution from these external magnetic diagnostic coil signals. This implementation of benchmarked against MSTFit, 2D Grad-Shafranov solver, axisymmetric...
The formulation of magnetic diagnostic response functions for a three-dimensional stellarator plasma is described. Reciprocity relations are used to compute unique each type diagnostic. Green’s function tables (databases) generated from which both external coil and internal current contributions signals can be rapidly computed. Applications compact stellarators
A non-parametric Gaussian process regression model is developed in the three-dimensional equilibrium reconstruction code V3FIT. a normal distribution of functions that uniquely defined by specifying mean function and covariance kernel function. assumes an unknown profile belongs to particular uses Bayesian analysis select give best fit measured data. The implementation V3FIT hybrid representation where processes are used infer some profiles standard parametric techniques remaining profiles....