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Fusion Research Center

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Now showing 1 - 10 of 65
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    A Tokamak Neutron Source for FFH Based on Iter Physics and Technology
    (Georgia Institute of Technology, 2009-10-16) Stacey, Weston M.
    Over the past decade the group at Georgia Tech has examined (Refs. 1-16) the application of a tokamak D-T fusion neutron source, based (insofar as possible) on the physics and technology of ITER, that could drive a sub-critical fast transmutation (burner) reactor fueled with the transuranics (TRU) from spent nuclear fuel (SNF). The purpose of such a reactor would be to stabilize the accumulation of spent fuel being discharged from LWRs by fissioning the TRU in SNF to significantly reduce the number of high-level-waste storage repositories required. Both gas-cooled reactors operating on a "burn and bury" non-reprocessing fuel cycle with TRISO TRU fuel (GCFTR) and liquid metal cooled reactors (SABR, FTWR) operating on a “reprocessing” fuel cycle with TRU metallic fuel have been considered, all driven by essentially the same tokamak neutron source. Determination of the required neutron source parameters for the SABR design is discussed here.
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    Interpretation of particle pinches and diffusion coefficients in the edge pedestal of DIII-D H-mode plasmas
    (Georgia Institute of Technology, 2009-10-15) Stacey, Weston M. ; Groebner, Rich J.
    A procedure is described for evaluating particle pinches to be used in interpreting particle diffusion coefficients from measured density and temperature profiles in the edge pedestal of tokamak plasmas. Application to the interpretation of two DIII-D [ J. Luxon, Nucl. Fusion 42, 614 (2002) ]. discharges yields new information about particle pinches and particle diffusion coefficient profiles in the edge pedestal.
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    Representation of the plasma fluid equations in "Miller equilibrium" analytical flux surface geometry
    (Georgia Institute of Technology, 2009-08-03) Stacey, Weston M. ; Bae, Cheonho
    The plasma fluid equations are represented explicitly in the magnetic flux surface coordinate system resulting from the analytical “Miller equilibrium” solution of the Grad–Shafranov equation. The magnetic geometry is characterized by the elongation, triangularity, and location of the displaced major radius of the flux surface. The resulting fluid equations can be solved directly without the necessity of first solving the Grad–Shafranov equation numerically to define the flux surface coordinates.
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    Rotation velocities in the plasma edge driven viscously by scrape-off layer flows
    (Georgia Institute of Technology, 2009-06-25) Stacey, Weston M.
    Scrape-off layer parallel flows and the viscous fluxes in the plasma edge driven thereby are calculated from neoclassical theory for a model problem representative of a present experiment, using an analytical model for elongated flux surface geometry with a Shafranov shift to provide a realistic evaluation of important poloidal dependences. The estimated effects of the viscous torques of toroidal and poloidal momentum driven by these scrape-off layer flows on rotation velocities in the edge plasma are substantial, suggesting possible explanations for various experimental observations.
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    An investigation of some effects of drifts and magnetic field direction in the scrape-off layer and divertor of tokamak plasmas
    (Georgia Institute of Technology, 2009-04-03) Stacey, Weston M.
    Various effects of particle drifts in the scrape-off layer (SOL) and divertor of tokamaks have been calculated. The predictions are consistent with several experimentally observed phenomena, e.g., the double reversal of parallel ion velocity in the SOL and the enhanced core penetration of argon injected into the divertor when the grad-B ion drift is into, rather than away from, the divertor. Other interesting phenomena, such as the structure of the parallel current flowing in the SOL and the reversal of the sign of the electrostatic potential in the SOL when the toroidal field direction is reversed, are also predicted.
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    Effect on the divertor and scrape-off layer plasma properties of the distribution of power and particle influxes from the core
    (Georgia Institute of Technology, 2009-03-25) Stacey, Weston M.
    Calculations of the profiles along the field lines within the divertor and scrape-off layer (SOL) of differences in the plasma ion density, temperature, parallel current, parallel flow velocity, and electrostatic potential, which result from using different poloidal distributions of the particle and heat influxes crossing the separatrix from the core plasma into the SOL, are presented and discussed vis-à-vis experimental observations. The calculations show that the stronger outboard than inboard particle and heat fluxes into the SOL caused by the geometric compression/expansion of flux surfaces predicted by magnetohydrodynamic equilibrium calculations lead to a prediction of higher plasma temperature at the outboard divertor than at the inboard divertor, a result that is consistent with experimental observation and that confirms a previous prediction (made without accounting for drifts) of a possible cause of the observed in-out divertor power asymmetry. The calculations also illustrate the effect of the poloidal distribution of particle and power influx into the SOL on the flow velocity, parallel current, and electrostatic potential distributions in the SOL and divertor.
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    A semi-automated procedure for creating geometry and background plasma input files for the GTNEUT 2d neutral particle transport code using the uedge plasma edge code
    (Georgia Institute of Technology, 2009-02) Friis, Zachary Ward
    The GTNEUT code1-3 can provide a computationally economical and accurate calculation of neutral particle transport in the complex 2D geometry to the tokamak divertor, scrapeoff layer and edge regions inside of the separatrix. However, the GTNEUT code requires a geometric input file describing this geometry and a background plasma file describing the plasma density and temperature in the various geometric regions. This report describes semi-automated procedures: i) for using (and extending) the input preparation capability of the UEDGE4-5 code to generate a GTNEUT geometric grid input file from a DIII-D EFIT file and ii) for using the plasma density and temperature distributions calculated with the UEDGE code to generate the background plasma input file for GTNEUT.
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    2009 Annual Report
    (Georgia Institute of Technology, 2009-01-01) Stacey, Weston M.
    Research Summary: During 2009, research focused on i) interpretation of plasma edge experiments in DIII-D (DoE Grant DE-FG02-99-ER54538), ii) further analysis of the SABR fusionfission hybrid actinide burner reactor concept developed at Georgia Tech (DoE Grant DE-SC0002202), and iii) related topics in theoretical/computation plasma physics. This work and publication/presentations based on it are summarized in this report.
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    Applications of the Miller equilibrium to extend tokamak computational models
    (Georgia Institute of Technology, 2008-12-11) Stacey, Weston M.
    An analytical model for the equilibrium flux surface geometry, widely known as the Miller equilibrium model, has been exploited to improve a variety of simplified tokamak computation models that incorporate an approximate flux surface geometry. Also discussed are improved models for an effective unelongated toroidal plasma representation of elongated flux surfaces; mapping temperature (and density) gradients measured at one poloidal location to other poloidal locations and to an average gradient over the flux surface; interpreting experimental heat diffusivities from local temperature gradients and average conductive heat fluxes; calculating the poloidal distribution of radial conductive heat fluxes; and evaluating the gyroviscous angular momentum transport rate.
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    Comparison of theoretical and experimental heat diffusivities in the DIII-D edge plasma
    (Georgia Institute of Technology, 2008-05-30) Stacey, Weston M.
    Predictions of theoretical models for ion and electron heat diffusivity have been compared against experimentally inferred values of the heat diffusivity profile in the edge plasma of two H-modes and one L-mode discharge in DIII-D J. Luxon, Nucl. Fusion 42, 614 2002 . Various widely used theoretical models based on neoclassical, ion temperature gradient modes, drift Alfvén modes and radiative thermal instability modes for ion transport, and based on paleoclassical, electron temperature gradient modes, trapped electron modes, and drift resistive ballooning modes for electron transport were investigated.