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  • 1
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    Study of High-Beta Magnetohydrodynamic Modes and Fast-Ion Losses in PDX. (1983)
    American Physical Society
    Details
    Publication Date: 1983-11-14
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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    PAPER CURRENT
  • 2
    Electronic Resource
    Electronic Resource
    Data analysis on TFTR using the SNAP transport code : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4753-4756 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes the between shots data analysis on TFTR using the one-dimensional equilibrium kinetic analysis code SNAP. SNAP accepts as input data: the measured plasma size and current, toroidal field, surface voltage, plasma composition (total Zeff and Zeff contribution from metallic impurities), edge neutral density, auxiliary heating power data (neutral beam power, energy, injection geometry and/or rf power and frequency), and measured profiles of Te(R), ne(R), Ti(R), Vφ(R), and Prad(R). SNAP iteratively calculates: (1) the mapping of profile data to a minor radius grid, (2) the magnetic topology including Shafranov shifted circular flux surfaces, (3) neutral beam attenuation and deposition profiles, (4) unthermalized beam ion density and beam power density delivered to thermal plasma species from a numerical solution to the Fokker–Planck equation, (5) the neutral density profile, (6) local heat and particle transport coefficients consistent with the measured profiles and calculated source terms, (7) ICRF power profiles from a reduced order full wave analysis and isotropic Stix quasilinear model, and (8) total neutron emissivity and plasma stored energy. Several ion heat transport models (including neoclassical χi and χi∝χe) are available to calculate an expected Ti(r) profile in the absence of measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143630
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  • 3
    Electronic Resource
    Electronic Resource
    Recent advances in the design of quasiaxisymmetric stellarator plasma configurations : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2083-2094 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strategies for the improvement of quasiaxisymmetric stellarator configurations are explored. Calculations of equilibrium flux surfaces for candidate configurations are also presented. One optimization strategy is found to generate configurations with improved neoclassical confinement, simpler coils with lower current density, and improved flux surface quality relative to previous designs. The flux surface calculations find significant differences in the extent of islands and stochastic regions between candidate configurations. (These calculations do not incorporate the predicted beneficial effects of perturbed bootstrap currents.) A method is demonstrated for removing low order islands from candidate configurations by relatively small modifications of the configuration. One configuration is identified as having particularly desirable properties for a proposed experiment. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1351826
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  • 4
    Electronic Resource
    Electronic Resource
    Ripple-induced energetic particle loss in tokamaks (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3043-3054 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The threshold for stochastic transport of high energy trapped particles in a tokamak due to toroidal field ripple is calculated by explicit construction of primary resonances, and a numerical examination of the route to chaos. Critical field ripple amplitude is determined for loss. The expression is given in magnetic coordinates and makes no assumptions regarding shape or up-down symmetry. An algorithm is developed including the effects of prompt axisymmetic orbit loss, ripple trapping, convective banana flow, and stochastic ripple loss, which gives accurate ripple loss predictions for representative Tokamak Fusion Test Reactor [R. Hawryluk, Plasma Phys. Controlled Fusion 33, 1509 (1991)] and International Thermonuclear Experimental Reactor [K. Tomabechi, Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research (International Atomic Energy Agency, Vienna, 1989), Vol. 3, p. 214] equilibria. The algorithm is extended to include the effects of collisions and drag, allowing rapid estimation of alpha particle loss in tokamaks. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871641
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  • 5
    Electronic Resource
    Electronic Resource
    Physics of the steady-state advanced tokamak (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1794-1802 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The tokamak reactor becomes a more attractive fusion power source if it can operate in steady state, and at high fusion power density, with low recirculating power. This implies that a "steady-state advanced tokamak'' must achieve both high beta and high confinement, consistent with a high fraction of the total plasma current being carried by the bootstrap effect. The most attractive mode of operation to fulfill these requirements involves a reversal of the global magnetic shear, dq/dr, in the plasma core. This allows self-consistency between the radial profile of the bootstrap current and that of the total current, while simultaneously reducing turbulent transport in the plasma core and increasing magnetohydrodynamic (MHD) stability. In this paper both theoretical and experimental work on the steady-state advanced tokamak are reviewed, and we point to new research areas that need to be pursued to make this concept a reality. Presently operating devices can make strong contributions in this research area, and future devices should be designed with the capability to access, investigate, and exploit this operating mode. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871698
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  • 6
    Electronic Resource
    Electronic Resource
    Physics issues in the design of high-beta, low-aspect-ratio stellarator experiments : The 41st annual meeting of the division of plasma physics of the american physical society (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 1911-1918 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-beta, low-aspect-ratio ("compact") stellarators are promising solutions to the problem of developing a magnetic plasma configuration for magnetic fusion power plants that can be sustained in steady state without disrupting. These concepts combine features of stellarators and advanced tokamaks and have aspect ratios similar to those of tokamaks (2–4). They are based on computed plasma configurations that are shaped in three dimensions to provide desired stability and transport properties. Experiments are planned as part of a program to develop this concept. A β=4% quasi-axisymmetric plasma configuration has been evaluated for the National Compact Stellarator Experiment (NCSX). It has a substantial bootstrap current and is shaped to stabilize ballooning, external kink, vertical, and neoclassical tearing modes without feedback or close-fitting conductors. Quasi-omnigeneous plasma configurations stable to ballooning modes at β=4% have been evaluated for the Quasi-Omnigeneous Stellarator (QOS) experiment. These equilibria have relatively low bootstrap currents and are insensitive to changes in beta. Coil configurations have been calculated that reconstruct these plasma configurations, preserving their important physics properties. Theory- and experiment-based confinement analyses are used to evaluate the technical capabilities needed to reach target plasma conditions. The physics basis for these complementary experiments is described. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874015
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  • 7
    Electronic Resource
    Electronic Resource
    Scaling of Ohmic energy confinement with major radius in the Tokamak Fusion Test Reactor (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 3996-4001 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ohmic plasma size scans have been carried out in the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)] to measure the influence of the major radius upon energy confinement. The major radius, minor radius, and aspect ratio were varied over wide ranges (R=2.08–3.2 m, a=0.4–0.9 m, and R/a=2.9–8.0) at constant qc. The energy confinement determined from kinetic diagnostics varies strongly with major radius. The data set is less well suited to determine minor radius scaling, but it appears to be distinctly weaker than the major radius scaling. The anomaly in ion thermal conductivity over neoclassical predictions appears to decline with increasing aspect ratio, which is a better ordering parameter for the magnitude of the anomaly than either the minor radius or the major radius. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870869
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  • 8
    Electronic Resource
    Electronic Resource
    Enhanced confinement in tokamaks (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 2941-2960 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The physics of enhanced confinement regimes in tokamaks is reviewed and some directions for further enhancements are assessed. The H-mode confinement regime is examined. A number of other observations of enhanced confinement, having in common peaked density profiles, are compared to the theory of ion temperature gradient modes. Two schemes of promise in enhancing confinement, second stability and control of electric fields, are discussed. The contributions of alternate concepts to understanding tokamak transport are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859361
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  • 9
    Electronic Resource
    Electronic Resource
    Neoclassical transport of energetic minority tail ions generated by ion-cyclotron resonance heating in tokamak geometry (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 2383-2394 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neoclassical transport of energetic minority tail ions, which are generated by high-powered electromagnetic waves of the ion cyclotron range of frequencies (ICRF) at the fundamental harmonic resonance, is studied analytically in tokamak geometry. The effect of Coulomb collisions on the tail-ion transport is investigated in the present work. The total tail-ion transport will be the sum of the present collision-driven transport and the wave-driven transport, which is due to the ICRF-wave scattering of the tail particles as reported in the literature. The transport coefficients have been calculated kinetically, and it is found that the large tail-ion viscosity, driven by the localized ICRF-heating and Coulomb slowing-down collisions, induces purely convective particle transport of the tail species, while the energy transport is both convective and diffusive. The rate of radial particle transport is shown to usually be small, but the rate of radial energy transport is larger and may not be negligible compared to the Coulomb slowing-down rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859504
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  • 10
    Electronic Resource
    Electronic Resource
    Correlations of heat and momentum transport in the TFTR tokamak (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1300-1305 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the toroidal rotation speed vφ(r) driven by neutral beam injection in tokamak plasmas and, in particular, simultaneous profile measurements of vφ, Ti, Te, and ne, have provided new insights into the nature of anomalous transport in tokamaks. Low-recycling plasmas heated with unidirectional neutral beam injection exhibit a strong correlation among the local diffusivities, χφ≈χi〉χe. Recent measurements have confirmed similar behavior in broad-density L-mode plasmas. These results are consistent with the conjecture that electrostatic turbulence is the dominant transport mechanism in the tokamak fusion test reactor tokamak (TFTR) [Phys. Rev. Lett. 58, 1004 (1987)], and are inconsistent with predictions both from test-particle models of strong magnetic turbulence and from ripple transport. Toroidal rotation speed measurements in peaked-density TFTR "supershots'' with partially unbalanced beam injection indicate that momentum transport decreases as the density profile becomes more peaked. In high-temperature, peaked-density plasmas the observed gradient scale length parameter ηtoti=d ln Ti/d ln ne correlates reasonably well with predictions of the threshold for exciting ion-temperature-gradient-driven turbulence (ITGDT), as would be expected for plasmas at marginal stability with respect to this strong transport mechanism. In L-mode plasmas where ITGDT is expected to be too weak to enforce marginal stability, ηtoti exceeds this threshold considerably. However, preliminary experiments have failed to observe a significant increase in ion heat transport when ηtoti was rapidly forced above ηc (the threshold for exciting ITGDT) using a perturbative particle source, as would have been expected for a plasma at marginal stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859545
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