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  • 1
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The predictions of gyrokinetic and gyrofluid simulations of ion-temperature-gradient (ITG) instability and turbulence in tokamak plasmas as well as some tokamak plasma thermal transport models, which have been widely used for predicting the performance of the proposed International Thermonuclear Experimental Reactor (ITER) tokamak [Plasma Physics and Controlled Nuclear Fusion Research, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 1, p. 3], are compared. These comparisons provide information on effects of differences in the physics content of the various models and on the fusion-relevant figures of merit of plasma performance predicted by the models. Many of the comparisons are undertaken for a simplified plasma model and geometry which is an idealization of the plasma conditions and geometry in a Doublet III-D [Plasma Physics and Controlled Nuclear Fusion Research, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159] high confinement (H-mode) experiment. Most of the models show good agreements in their predictions and assumptions for the linear growth rates and frequencies. There are some differences associated with different equilibria. However, there are significant differences in the transport levels between the models. The causes of some of the differences are examined in some detail, with particular attention to numerical convergence in the turbulence simulations (with respect to simulation mesh size, system size and, for particle-based simulations, the particle number). The implications for predictions of fusion plasma performance are also discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3804-3819 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Inertial electrostatic confinement (IEC) systems are predicated on a nonequilibrium ion distribution function. Coulomb collisions between ions cause this distribution to relax to a Maxwellian on the ion–ion collisional time scale. The power required to prevent this relaxation and maintain the IEC configuration for times beyond the ion–ion collisional time scale is shown to be greater than the fusion power produced. It is concluded that IEC systems show little promise as a basis for the development of commercial electric power plants. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 1988-1998 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The beta limits on the central cells of nonaxisymmetric tandem mirrors due to moderate-m ballooning modes are studied. Both finite Larmor radius (FLR) effects and corrections associated with the finite extent of the ballooning modes in the plane perpendicular to B are retained. The assumption of short perpendicular wavelength together with the large ellipticity of the flux surfaces near the magnetohydrodynamic (MHD) anchor cells allows a reduction of the three-dimensional problem into a sequence of three one-dimensional problems. The marginal stable boundary for the Mirror Fusion Test Facility (MFTF-B) (National Technical Information Service Document Nos. 82020108 and UCID-19359) is calculated and compared with that obtained from a low mode number calculation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 1416-1428 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: From a set of fluid equations, a second-order differential equation, governing the resistive ballooning instability for a mirror confined plasma with a rigid perturbation, is obtained. The resistive effects on the rigid mode ballooning instability are numerically examined for three tandem mirror configurations; those stabilized by walls, by end cusps, and by end quadrupoles. In the model the pressure is taken to be isotropic and constant along the axis except in the cusps and the diverging field regions, and the plasma has a sharp boundary. The theoretical results indicate that the resistivity can play a major role in determining the growth rate for ballooning for lower temperature devices.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2824-2837 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dissipative trapped particle modes are studied in tandem mirrors by including electron collisions and ion Landau damping. A variational approach is used to obtain a collisional response in terms of the collisionless result plus a collisional term. The collisional term is then self-consistently solved in all collision frequency regimes. When ν/ω(very-much-less-than)1 (ν≡electron collision frequency) and the dissipationless mode is stable through a positive (negative) charge uncovering mechanism, there are two stable waves with phase velocities in the ion (electron) diamagnetic direction. The higher frequency wave with ω∼ω@B|i(ω*e) is destabilized by ion (electron) dissipation while the lower frequency wave is destabilized by electron (ion) dissipation. At high collision frequency (ν〉ω@B|e), the only unstable trapped particle wave has ω∼ω*e, with electron collisions being destabilizing.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2248-2257 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent experiments on the TMX-U device at the Lawrence Livermore National Laboratory have indicated the possibility of a low-frequency (ω(very-much-less-than)Ωci) drift wave being driven unstable by the injection of neutral beams in the thermal barrier region. Nonlocal linear theory is performed for this instability using slab geometry and the electrostatic approximation. Particle simulations are used to verify the linear theory and to recover relevant nonlinear phenomena. Important nonlinear effects include: (1) E×B trapping (2) relaxation of the beam density profiles, and (3) weakly nonlinear electrons (eδφ/Te ≈0.1). These nonlocal simulations are compared with previous simulations of Ref. 1 [Phys. Fluids 28, 2235 (1985)] which used a local approximation for the particle simulations.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 1578-1586 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tandem-mirror trapped-particle modes are studied in a model system consisting of two connected square wells representing the solenoid and the end cells. Collisions are described by a Lorentz operator. A dispersion relation that is valid for arbitrary ν/ω (ω=wave frequency, ν=collision frequency) is derived. Four limits are investigated. When ε≡νRam/ω (very-much-less-than)1+pi/pe, where Ram is the mirror ratio separating electrons trapped in the anchor from those passing to the solenoid and pe and pi are the fractions of passing electrons and ions, collisions destabilize a trapped-particle mode that is stable in the collisionless limit; the growth rate is proportional to ε1/2 for ε(very-much-less-than)1 and ε/ln ε for 1+pi/pe (very-much-greater-than)ε(very-much-greater-than)1. When ε (very-much-greater-than)1+pi/pe, the trapped-particle mode becomes a weakly growing drift wave with growth rate proportional to ε−1 ln ε for ν/ω(very-much-less-than)1 and ν−1 for ν/ω(very-much-greater-than)1; additionally identified are two flute modes, one of which is unstable for some parameters, and a strongly damped high-frequency mode.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2235-2247 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent experiments on the TMX-U device, at the Lawrence Livermore National Laboratory have indicated the possibility of a drift wave being driven unstable by the injection of neutral beams in the thermal barrier region. A review of linear theory is presented in the local approximation. In addition, particle simulations are used to understand the nonlinear characteristics of this instability. The particle simulations are performed using 1d-3v and 2d-3v electrostatic particle simulation codes. The instability is shown to saturate by beam trapping, nonlinear electron effects, and nonlinear motion parallel to the density gradient. Resonant E×B motion is a significant process for some of the beam particles. This process is closely associated with the trapping of beam ions. Harmonic generation is also observed, as appears in some of the experimental data. Qualitative nonlinear theory is presented in support of the particle simulations.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1572-9591
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Tokamak Physics Experiment is designed to develop the scientific basis for a compact and continuously operating tokamak fusion reactor. It is based on an emerging class of tokamak operating modes, characterized by beta limits well in excess of the Troyon limit, confinement scaling well in excess of H-mode, and bootstrap current fractions approaching unity. Such modes are attainable through the use of advanced, steady state plasma controls including strong shaping, current profile control, and active particle recycling control. Key design features of the TPX are superconducting toroidal and poloidal field coils; actively-cooled plasma-facing components; a flexible heating and current drive system; and a spacious divertor for flexibility. Substantial deuterium plasma operation is made possible with an in-vessel remote maintenance system, a lowactivation titanium vacuum vessel, and shielding of ex-vessel components. The facility will be constructed as a national project with substantial participation by U.S. industry. Operation will begin with first plasma in the year 2000.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of fusion energy 17 (1998), S. 25-32 
    ISSN: 1572-9591
    Keywords: Confinement requirements ; advanced fuels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The energy confinement requirements for burning D-3He, D-D, or P-11B are reviewed, with particular attention to the effects of helium ash accumulation. It is concluded that the DT cycle will lead to the more compact and economic fusion power reactor. The substantially less demanding requirements for ignition in DT (the ne τE T required for ignition in DT is smaller than that of the nearest advanced fuel, D-3He, by a factor of 50) will allow ignition, or significant fusion gain, in a smaller device; while the higher fusion power density (the fusion power density in DT is higher than that of D-3He by a factor of 100 at the same plasma pressure) allows for a more compact and economic device at fixed fusion power.
    Type of Medium: Electronic Resource
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