Organizational Unit:
Fusion Research Center

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Now showing 1 - 10 of 84
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    SABR Subcritical Advanced Burner Reactor
    (Georgia Institute of Technology, 2007-10) Stacey, Weston M. ; Georgia Institute of Technology. School of Physics ; Georgia Institute of Technology. Fusion Research Center
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    Investigation of edge pedestal structure in DIII-D (DoE Grant ER54538)
    (Georgia Institute of Technology, 2005-10) Stacey, Weston M. ; Groebner, Rich J. ; Georgia Institute of Technology. Fusion Research Center
    A calculation based on the requirements of particle, momentum and energy conservation, conductive heat transport and atomic physics resulting from a recycling and fueling neutral influx was employed to investigate the experimental density, temperature, rotation velocities and radial electric field profiles in the edge of three DIII-D [J. Luxon, Nucl. Fusion, 42, 614 (2002)] high-mode plasmas. The calculation indicated that the cause of the pedestal structure in the density was a momentum balance requirement for a steep negative pressure gradient to balance the forces associated with an edge peaking in the inward pinch velocity (caused by the observed edge peaking in the radial electric field and rotation velocity profiles) and, to a lesser extent, in the outward radial particle flux (caused by the ionization of recycling neutrals). Thermal and angular momentum transport coefficients were inferred from experiment and compared with theoretical predictions, indicating that thermal transport coefficients were of the magnitude predicted by neoclassical and ion-temperature-gradient theories (ions) and electrontemperature- gradient theory (electrons), but that neoclassical gyroviscous theory plus atomic physics effects combined were not sufficient to explain the inferred angular momentum transfer rate throughout the edge region.
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    2005 Annual Report Fusion Research Center Georgia Institute of Technology [Title page and table of contents]
    (Georgia Institute of Technology, 2005-10) Stacey, Weston M. ; Georgia Institute of Technology. Fusion Research Center
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    A Superconducting Tokamak Fusion Transmutation of Waste Reactor
    (Georgia Institute of Technology, 2004-01) Stacey, Weston M. ; Mauer, A. N. ; Mandrekas, John ; Hoffman, E. A. (Elisha Albright)
    We are developing a Fusion Transmutation of Waste Reactor (FTWR) concept—a sub-critical, metal fuel, liquid metal cooled fast reactor driven by a tokamak DT fusion neutron source. An emphasis is placed on using nuclear, separation/processing and fusion technologies that either exist or are at an advanced state of development and on using plasma physics parameters that are supported by the existing database. We have previously discussed the general capabilities of DT tokamak neutron sources for driving transmutation reactors [1] and developed a design concept for a FTWR [2] based on normal conducting magnets. The concept has been further developed in papers dealing with nuclear design and safety [3] and with the evaluation of the potential impact on radioactive waste management [4]. The purpose of this paper is to examine how the FTWR design concept would change if superconducting magnets were used.
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    Interpretation of edge pedestal rotation measurements in DIII-D
    (Georgia Institute of Technology, 2008-01-25) Stacey, Weston M. ; Groebner, Rich J. ; Georgia Institute of Technology. School of Physics ; Georgia Institute of Technology. Fusion Research Center ; General Atomics
    A novel methodology for inferring experimental toroidal angular momentum transfer rates from measured toroidal rotation velocities and other measured quantities has been developed and applied to analyze rotation measurements in the DIII-D J. Luxon, Nucl. Fusion 42, 6149 2002 edge pedestal. The experimentally inferred values have been compared with predictions based on atomic physics processes and on neoclassical toroidal viscosity. The poloidal rotation velocities have been calculated from poloidal momentum balance using neoclassical parallel viscosity and a novel retention of all terms in the poloidal momentum balance, and compared with measured values in the DIII-D edge pedestal.
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    The Effect of Ion Orbit Loss and X-Loss on the Interpretation of Ion Energy and Particle Transport in the DIII-D Edge Plasma
    (Georgia Institute of Technology, 2011-10-14) Stacey, Weston M. ; Georgia Institute of Technology. School of Physics ; Georgia Institute of Technology. Fusion Research Center
    Calculation models are presented for treating ion orbit loss effects in interpretive fluid transport calculations for the tokamak edge pedestal. Both standard ion orbit loss of particles following trapped or passing orbits across the separatrix and the X-loss of particles that are poloidally trapped in a narrow null-Bθ region extending inward from the X-point, where they gradB and curvature drift outward, are considered. Calculations are presented for a representative DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] shot which indicate that ion orbit loss effects are significant and should be taken into account in calculations of present and future experiments.
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    Sub-critical Transmutation Reactors with Tokamak Fusion Neutron Sources
    (Georgia Institute of Technology, 2005) Stacey, Weston M. ; Mandrekas, John ; Hoffman, E. A. (Elisha Albright)
    The principal results of a series of design scoping studies of sub-critical fast transmutation reactors (based on the nuclear and processing technology being developed in the USDoE Generation IV, Advanced Fuel Cycle and Next Generation Nuclear Plant programs) coupled with a tokamak fusion neutron source (based on the ITER design basis physics and technology) are presented.
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    Higher Order Approximations of the TEP Method for Neutral Particle Transport in Edge Plasmas
    (Georgia Institute of Technology, 2006) Stacey, Weston M. ; Zhang, Dingkang ; Mandrekas, John
    Higher order approximations, which take into account the effects of angular anisotropy, spatial non-uniformity and energy dependence of the distribution of neutral particles, have been developed and implemented to extend the range of validity of the Transmission and Escape Probabilities (TEP) method for the calculation of neutral particle transport in plasmas. Comparisons with Monte Carlo calculations of model test problems and DIII-D L- and H- mode discharges show that these new extensions significantly improve the accuracy and extend the range of validity of the TEP methodology.
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    Force Balance and Ion Particle Transport Differences in High and Low Confinement Tokamak Edge Pedestals
    (Georgia Institute of Technology, 2010-11-22) Stacey, Weston M. ; Groebner, Rich J. ; Georgia Institute of Technology. School of Physics ; Georgia Institute of Technology. Fusion Research Center ; General Atomics
    The various terms in the radial force balance in the edge plasma are evaluated using experimental data from the low (L) and high (H) confinement phase of a DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] discharge in order to investigate the differences in the radial force balance among the several electromagnetic and pressure gradient forces in L-mode and H-mode. The roles of cross-field toroidal momentum transport and of a radial pinch velocity in determining different radial particle fluxes in L-mode and H-mode are elucidated
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    Poloidal rotation and density asymmetries in a tokamak plasma with strong toroidal rotation
    (Georgia Institute of Technology, 1992-10) Stacey, Weston M. ; Georgia Institute of Technology. School of Physics ; Georgia Institute of Technology. Fusion Research Center
    A neoclassical model for calculating poloidal rotation and poloidal density asymmetries in a tokamak plasma with vϕ∼vth and E/Bθ∼O(1) is developed. Application is made to the analysis of a deuterium plasma with a dominant carbon impurity. The dependences of the results on collisionality, the anomalous radial deuterium flux and the toroidal rotation speed are evaluated. The implications of the calculated poloidal velocities and density asymmetries for the magnitude of the gyroviscous torque are discussed.