A5081206197- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Fusion materials and technologies
- Magnetic Field Sensors Techniques
- Laser-induced spectroscopy and plasma
- Combustion and flame dynamics
- Solar and Space Plasma Dynamics
- Nuclear Physics and Applications
- Nuclear reactor physics and engineering
- Adsorption and Cooling Systems
- Computational Fluid Dynamics and Aerodynamics
- Engineering Education and Pedagogy
- Particle Accelerators and Free-Electron Lasers
- Thermodynamic and Exergetic Analyses of Power and Cooling Systems
- Radiative Heat Transfer Studies
- Atomic and Molecular Physics
- Astro and Planetary Science
- Membrane Separation Technologies
- Fire dynamics and safety research
- Energy Efficiency and Management
- Iron and Steelmaking Processes
North Carolina State University
2005-2023
Idaho National Laboratory
2022
Laboratoire d’Imagerie Biomédicale
2015
North Central State College
2011
University of California, Los Angeles
2001-2004
Princeton University
2003-2004
Princeton Plasma Physics Laboratory
2003-2004
University of Wisconsin–Madison
2002-2003
University of California, Berkeley
2003
University of California, Davis
1998-2001
Experimental evidence for a positive correlation is established between the magnitude of electromagnetic fluctuations up to lower-hybrid frequency range and enhancement reconnection rates in well-controlled laboratory plasma. The belong right-hand polarized whistler wave branch, propagating obliquely reconnecting magnetic field, with phase velocity comparable relative drift electrons ions. measured short coherence lengths indicate their strongly nonlinear nature.
Reduction of core-resonant m=1 magnetic fluctuations and improved confinement in the Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch have been routinely achieved through control surface poloidal electric field, but it is now known that has limited part by edge-resonant m=0 fluctuations. Now, refined field control, plus toroidal possible to reduce simultaneously This allowed high-energy runaway electrons, possibly indicative flux-surface...
New developments in Faraday rotation polarimetry have provided the first measurements of current density profile and core magnetic fluctuations a high-temperature reversed field pinch. This has been achieved by fast-polarimeter system with time response up to 1 μs phase resolution <1 mrad. Recent experiments on Madison Symmetric Torus directly measured radial plasma interior amplitude 33 G, ∼1%. A broad spectrum is observed 100 kHz. Relaxation at sawtooth crash occurs timescale μs....
New profile measurements have allowed the electron thermal diffusivity to be estimated from power balance in Madison Symmetric Torus where magnetic islands overlap and field lines are stochastic. The show that (1) energy transport is conductive not convective, (2) measured diffusivities good agreement with numerical simulations of stochastic transport, (3) greatly reduced near reversal surface diffusion small.
Energy confinement comparable with tokamak quality is achieved in the Madison Symmetric Torus (MST) reversed field pinch (RFP) at a high beta and low toroidal magnetic field. Magnetic fluctuations normally present RFP are reduced via parallel current drive outer region of plasma. In response, electron temperature nearly triples doubles. The time increases ten-fold (to ∼10 ms), which L- H-mode scaling values for same plasma current, density, heating power, size shape. Runaway evidenced by...
First measurements of the current-density profile in core a high-temperature reversed-field pinch are presented. The is observed to peak during sawtooth cycle and broaden promptly at crash. This change can be linked magnetic relaxation dynamo which predicted drive antiparallel current plasma core. For high-confinement discharges, suppressed strongly peak.
Magnetic field fluctuations (and the associated current perturbation) have been measured in core of a high-temperature reversed-field pinch using newly developed fast-polarimetry system. Radial magnetic fluctuation levels approximately 1% are standard-reversed-field discharges which increase to 4% during sawtooth crash (enhanced dynamo). The level is reduced fourfold for high-confinement plasmas where core-resonant tearing modes suppressed.
The multichannel far-infrared (FIR) heterodyne polarimeter-interferometer system on the Madison Symmetric Torus (MST) is now operational. combined consists of 11 channels with variable radial and toroidal spacing. Poloidal magnetic field determined by measuring Faraday rotation FIR laser beam after propagation through plasma use a phase technique. polarimeter has 3 mrad rms noise level 1 ms temporal resolution while interferometer nedl=1×1012 cm−2 time response μs. Absolute calibration...
Confinement of runaway electrons has been observed for the first time in a reversed field pinch during improved-confinement plasmas Madison Symmetric Torus. Energy-resolved hard-x-ray flux measurements have used to determine velocity dependence electron diffusion coefficient, utilizing computational solutions Fokker-Planck transport equation. With improved-confinement, fast diffusivity drops by 2 orders magnitude and is independent velocity. This suggests change mechanism away from...
The increased penetration of intermittent renewable energy technologies such as wind and solar power can strain electric grids, forcing carbon-based nuclear sources to operate in a load-follow mode. For reactors, operation be undesirable due the associated thermal mechanical stresses placed on fuel other reactor components. Various methods storage (TES) coupled (or renewable) help absorb grid variability caused by daily load demand changes intermittency. Two TES techniques are investigated...
The design and operation of a spheromak-like compact toroid (SCT) plasma accelerator is described. As an example application, some principles are presented for using the device as injector to fuel tokamak plasma. forms accelerates SCT self-contained structure with embedded poloidal toroidal magnetic fields their associated currents that provide confinement structural integrity. formed in magnetized coaxial gun then accelerated within electrodes. typical mass fueling from several tens...
ABSTRACT This study presents the results of experiments designed to investigate flame lift-off behavior nozzle velocity, co-flow fuel-type, and size for low Reynolds Number turbulent flows (in near hysteresis regime). Local excess jet velocities are computed using relations from Tieszen et al. The show that local velocity remains linear with respect through most regime, even though height is not linear. suggests a non-linear relation captured by Kalghatgi (Citation1984) in field regime. at...
A study of the characteristics turbulent lifted-jet flames in hysteresis regime was performed using methane and ethylene fuels laminar air coflows. Reattachment velocities lifted flame heights just prior to reattachment vary linearly as for coflow. The flow coflow (i.e., or turbulent) did not appear affect behavior these flames. These observations are utility designing maximum turndown burners coflow, especially determining stability criteria low fuel-flow applications.
Air-conditioning loads during the warmer months of year are large contributors to an increase in daily peak electrical demand. Traditionally, utility companies boost output meet cooling load spikes, often using expensive and polluting fossil fuel plants match Likewise, heating, ventilation, air conditioning (HVAC) system components must be sized these loads. However, use a properly stratified chilled-water storage conjunction with conventional HVAC can shift energy peaks from off-peak hours....
Presented are the results of experiments designed to investigate flame lift-off behavior in hysteresis regime for low Reynolds number turbulent flows. The refers situation where jet has dual positions favorable stabilization: attached and lifted. Typically, a is lifted off burner stabilized at some downstream location pair fuel coflow velocities that unique position. Since direction from which condition arrived important, there an inherent hysteretic behavior. To supplement previous research...
Work on the acceleration of a compact toroid plasma configuration between coaxial electrodes is reported. In experiment maximum poloidal field component and full width at half are shown to increase decrease with accelerator voltage, respectively. The velocity voltage then saturate as increased above approximately 11 kV. saturation in components due crowbarring insulator. insulator consistent onset `blowby' effect, which most likely triggering source.
The current profile and core magnetic field fluctuation amplitudes in a reversed-field pinch are measured by using high-resolution polarimetry–interferometry system. This paper presents data showing redistribution of the during sawtooth crash. Also, amplitude is observed to increase at crash consistent with idea nonlinearly driven dynamo current. In addition, parallel density increases outer region plasma auxiliary pulsed drive. was expected, as external application an edge electric designed...
A compact pellet injection system that was recently developed at the Oak Ridge National Laboratory has been installed on Madison Symmetric Torus (MST) University of Wisconsin and used in initial plasma fueling experiments. The system, referred to as a “pellet injector suitcase,” is pipe gun device with four-barrel capability (presently equipped two 1.0-mm-bore barrels), it uses cryogenic refrigerator for in-situ hydrogen formation (typically, D2 pellets). This new, portable, stand-alone...
Recent experiments using accelerated spheromak-like compact toroids (SCTs) to fuel tokamak plasmas have quantified the penetration mechanism in low beta regime; i.e. external magnetic field pressure dominates plasma thermal pressure. However, fusion reactor designs require high and, more importantly, proper profile. Here, effect of profile on SCT penetration, specifically, diamagnetism, is addressed. It estimated that even up 50% local beta. The combination diamagnetic toroidal and strong...
A miniature multichord soft-x-ray detection system has been installed on the Madison Symmetric Torus (MST) reversed-field pinch to study plasma equilibrium and fluctuation properties of standard- improved-confinement discharges. Because relatively flat MST density temperature profiles, spatial resolution is poor along line sight. However, can resolve line-integrated-emissivity fluctuations which are strongly correlated with rotating m=1 global magnetic as well heat pulse propagation...
A compact toroid inductively stores the energy released by a capacitor bank as it is being accelerated. This can be stored for period of more than ten microseconds and then transferred to load on much shorter time scale. article presents framing camera images radial compression plasma trailing behind leaves its inner electrode. illustrates basic principles opening switch which could used drive fast z pinches.