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  • 1
    Electronic Resource
    Electronic Resource
    Neoclassical kinetic theory near an X point: Plateau regime (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 548-551 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Traditionally, neoclassical transport calculations ignore poloidal variation of the poloidal magnetic field. Near an X point of the confining field of a diverted plasma, the poloidal field is small, causing guiding centers to linger at that poloidal position. A study of how neoclassical transport is affected by this differential shaping is presented. The problem is solved in general in the plateau regime, and a model poloidal flux function with an X point is utilized as an analytic example to show that the plateau diffusion coefficient can change considerably (factor of 2 reduction). Ion poloidal rotation is proportional to the local value of Bpol but otherwise it is not strongly affected by shaping. The usual favorable scaling of neoclassical confinement time with plasma current is unaffected by the X point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870799
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of asymmetric sources on tokamak neoclassical transport in the plateau regime (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 2113-2117 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A plasma source is present in the edge of tokamak plasmas that can modify neoclassical flows and fluxes, including the self-consistent value of the electric field. The usual neoclassical assumption of divergenceless flows yields well-known equilibrium rotation rates; equilibrium rotation in the presence of sources, however, can be very different. In order to study this problem when toroidal symmetry is broken a kinetic approach is necessary. Estimates from TEXT [Nucl. Technol./Fusion 1, 479 (1981)] indicate that the source term in the drift kinetic equation is of the same order as the guiding center drift frequency. The drift kinetic equation is solved in the plateau regime with toroidally and poloidally localized sources. A modification of the radial and parallel neoclassical flows is obtained. Possible implications for L–H transitions are studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859431
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of charge exchange on plasma flows (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2675-2676 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple drift-kinetic derivation of the expressions for the poloidal ion and impurity flows in the presence of charge-exchange drag and ion-impurity collisions is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860187
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  • 4
    Electronic Resource
    Electronic Resource
    Rotation in Ohmically heated tokamaks: Experiment and theory (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2485-2490 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Comparison of experiments with theory leads to a reasonably complete understanding of impurity rotation in Ohmic plasmas in a tokamak. In the experiments, the components of the impurity rotation velocity were derived from measurements of the Doppler shift of carbon spectral emission. Neoclassical theory for rotation was evaluated using measured plasma profiles and compared with experiment. The comparisons suggest that plasma toroidal rotation is damped (but not quenched) by momentum loss due to ion–neutral charge exchange and that the damping can now be accurately predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860733
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  • 5
    Electronic Resource
    Electronic Resource
    A study for the installation of the TEXT heavy-ion beam probe on DIII-D : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 320-323 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An assessment of the feasibility of installing the TEXT 2 MeV heavy-ion beam probe on the DIII-D tokamak has been completed. Detailed drawings of the machine cross section were imported into the CAD application AutoCAD. A set of programs written in AutoLisp were used to generate trajectories. Displays of the accessible cross section of the plasma, scan lines for the entire range of primary beam energy and injection angle ranges, and sample–volume dimensions can be rapidly generated. Because of the large deflection between the primary input beam and the emergent secondary beam, either the analyzer needs to be tracked over a ±20° angle or secondary poloidal deflector plates need to be installed at the exit port. Toroidal deflector plates will be installed at both the injection and exit ports to compensate for toroidal displacements and deflections. The sample volumes generated by this procedure are within a few centimeters of the locations derived from a full three-dimensional calculation.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147860
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  • 6
    Electronic Resource
    Electronic Resource
    Inversion of chord-integrated data from noncircular tokamak plasmas (abstract)a) : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 460-460 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The superior performance of diverted and elongated plasmas in tokamaks motivates improvements of inversion techniques for chord integrated data (from interferometry, spectroscopy, bolometry, etc.) from such noncircular plasmas. We present a technique planned for TEXT-U. First, flux-surface contours are calculated using EFIT or a filament code. A computer subroutine is provided which then computes, for a given chord, the length of the chord segment enclosed within the flux surface ψ, as a function of ψ from the tangent surface ψtan outward. Using the length functions, the inversions may be performed using the technique of Park or by least-squares fitting. Inversions of FIR interferometer data are presented. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146382
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  • 7
    Electronic Resource
    Electronic Resource
    Vacuum compatible, variable cross-section magnetic coil diagnostic used in digital feedback control of plasma position in TEXT-Upgrade : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 461-463 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A magnetic pickup coil diagnostic set is used to measure the position of the plasma column in the Texas Experimental Tokamak Upgrade (TEXT-U) project. The output from this coil set is used in a digital feedback system to control the plasma position. To provide a fast time response for the feedback system, one complete coil set is located on the interior of the vacuum vessel. Another set with a slower time response is located on the outside of the vessel. To simplify and speed up data processing, the coils are constructed so that the X and Y coordinates of the plasma current centroid are each determined using the signals from only two separate coils. For each coordinate one coil is used to measure a tangential (relative to the coil surface) magnetic field component, while the second coil measures a normal field component. Due to physical constraints, the coils are not continuous around the vacuum vessel. The presence of gaps in the coils causes pickup of the external current flowing in the divertor coil windings during TEXT-U diverted discharges. This pickup has been successfully nulled out by adding a divertor current Rogowski coil to the X position coil circuit. The data indicate that these coils, along with the digital feedback system, are useful tools for flexible position control over a wide range of TEXT-U plasma parameters. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146383
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