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  • 1
    Electronic Resource
    Electronic Resource
    High luminous efficiency thin-film electroluminescent devices with low resistivity insulating materials (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1509-1512 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to fabricate high brightness and high efficiency thin-film electroluminescent (EL) devices, the emission characteristics of devices employing low resistivity and high dielectric constant materials, such as radio-frequency-sputtered HfO2 films, have been studied. It was found that the EL device with a glass/indium tin oxide/BaTiO3/ZnS:TbF3/HfO2/Ta2O5/HfO2/Al structure exhibited higher brightness and higher efficiency than the other devices. The highest luminous efficiency (η) and brightness of 0.9 lm/W and 1000 cd/m2, respectively, were obtained at 1-kHz sinusoidal wave voltage excitation. This was mainly due to the insulating layers adjacent to the active layer, which have low resistivity and high dielectric constant. So, it has higher density of interface states and deeper interface states at HfO2–ZnS and BaTiO3–ZnS interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351219
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  • 2
    Electronic Resource
    Electronic Resource
    Critical neutral density for high-mode bifurcation in tokamaks (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 1801-1803 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of a neutral population are included in the high-mode (H-mode) bifurcation theory [Phys. Rev. Lett. 63, 2369 (1989)]. It is shown that, for a given set of parameters, there exist critical values of neutral density above which H-mode bifurcation cannot occur. However, if the neutral density is fixed, for a given ion collisionality, this implies the existence of a critical ion temperature below which H-mode bifurcation cannot occur. These critical values can be tested experimentally. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871332
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  • 3
    Electronic Resource
    Electronic Resource
    Resonance parallel viscosity in the banana regime in poloidally rotating tokamak plasmas (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1168-1176 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Parallel viscosity in the banana regime in a poloidally (E×B) rotating tokamak plasma is calculated to include the effects of orbit squeezing and to allow the poloidal E×B Mach number Mp to have a value of order unity. Here, E is the electric field and B is the magnetic field. The effects of orbit squeezing not only modify the size of the particle orbit, but also change the fraction of poloidally trapped particles. Resonance between the particle parallel (to B) speed u and the poloidal component of the E×B velocity can only occur for those particles with energy (v/vt)2(approximately-greater-than)M2p (with v the particle speed and vt the thermal speed). Thus, the resonance parallel plasma viscosity in the banana regime decreases exponentially with M2p when M2p≥1, and has a local maximum of M2p∼1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870713
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  • 4
    Electronic Resource
    Electronic Resource
    Bootstrap current and ion thermal conductivity in an ultralow-aspect-ratio tokamak (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 349-351 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The bootstrap current Jb=−IcP'B/〈B2〉 and χi= (square root of)2NνiMiTi(Ic/e)2〈1/B2〉/||∇ψ ||2 are valid for both the banana and the Pfirsch–Schlüter regimes for any finite value of the collision frequency at a radius where the local aspect ratio A approaches unity. Here, I=RBt with R the major radius, Bt the toroidal magnetic field strength, and the prime denoting the derivative with respect to the poloidal flux ψ. Thus, the bootstrap current does not vanish, even in the collisional regime, when A approaches unity. The physical reason for this dramatic result is that the magnitudes of the electron and ion parallel viscosity approach infinity as A approaches unity. This also indicates that the conventional theory underestimates the magnitude of bootstrap current in an ultralow-aspect-ratio tokamak. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870961
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  • 5
    Electronic Resource
    Electronic Resource
    Orbit squeezing in a magnetic well (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2843-2845 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that the size of a charged particle's drift orbit is squeezed, i.e., reduced, in a magnetic well in tokamak plasmas. The squeezing factor depends on the energy of the particle, being larger for higher-energy particles. Therefore, for high-energy particles, the size of the drift orbit depends only on the magnetic geometry. These energy-independent drift orbits are also observed [J. A. Rome and Y.-K. M. Ping, Nucl. Fusion 19, 1193 (1979)]. The implications on the core confinement improvement physics and the confinement of the advanced fuel are discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871642
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  • 6
    Electronic Resource
    Electronic Resource
    An approximate analytic expression for plasma viscosity in finite aspect ratio tokamaks and its applications (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 965-970 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An approximate analytic expression for plasma viscosity in finite aspect ratio tokamaks is constructed from all the asymptotic limits. The resultant viscosity coefficient is compared with the numerical results of the solution of the linearized drift kinetic equation. Neoclassical fluxes are reformulated in terms of the viscosity and friction coefficients. These fluxes can be employed to study the omnigeneous property of high-beta small, or large aspect ratio tokamaks. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871801
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of orbit squeezing on poloidal mass flow and bootstrap current in tokamak plasmas (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 3365-3368 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown, by solving the drift kinetic equation, that the asymptotic values of the poloidal mass flow and the bootstrap current in the banana regime of large-aspect-ratio tokamak plasmas are not affected by orbit squeezing. However, because the definition of ion collisionality υ*i is reduced by a factor S−3/2, with S=1−(ρpid ln Er/dr) (cEr/Bpνti), the values of both the poloidal mass flow and the bootstrap current at the banana–plateau transition are different from those of the conventional neoclassical theory. Here, ρpi is the ion poloidal gyroradius, Er is the radial electric field, c is the speed of light, Bp is the poloidal magnetic strength, νti is the ion thermal speed, and r is the local radius. The implications for the experimental observations of poloidal rotation speeds in high mode (H mode) are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870484
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  • 8
    Electronic Resource
    Electronic Resource
    Time dependent parallel viscosity and relaxation rate of poloidal rotation in the banana regime (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 132-138 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time dependent ion parallel viscous force in the banana regime with arbitrary inverse aspect ratio ε is calculated using the eigenfunction approach. The flux surface averaged viscosity is then used to study the relaxation process of the poloidal rotation which leads to oscillatory relaxation behavior. The relaxation rate νp is found approximately proportional to νii/ε (where νii is the ion collision frequency and ε is the inverse aspect ratio).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870932
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  • 9
    Electronic Resource
    Electronic Resource
    Alpha-particle losses from toroidicity-induced Alfvén eigenmodes. Part II: Monte Carlo simulations and anomalous alpha-loss processes (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1506-1516 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fusion-born α particles moving parallel to the magnetic field can resonate with toroidal Alfvén eigenmodes (TAE) leading to anomalous α-orbit diffusion across the α-loss boundaries in a tokamak. This is analyzed using the Hamiltonian guiding center code orbit in conjunction with the kinetic magnetohydrodynamics (MHD) eigenmode solving code nova-k. Resonant single α orbits are studied below and above the threshold for orbit stochasticity and Monte Carlo randomized ensembles of alphas subjected to a finite amplitude time-dependent TAE are followed with respect to their radial losses using realistic MHD equilibria and numerically computed toroidal Alfvén eigenfunctions for one toroidal eigenmode n=1 and the full Fourier spectrum of poloidal harmonics m involved in the "gap mode.'' The α-loss mechanisms are resonant drift motion across the loss boundaries of alphas born near these boundaries and stochastic diffusion to the boundaries in constants of the motion (phase) space. After a first transient of resonant drift losses scaling as B˜r/B0, the number of alphas lost via diffusion scales as (B˜r/B0)2. For TAE amplitudes B˜r/ B0≥10−3, α orbit stochasticity sets in and, depending on the radial width of the fast α density nα(r), a substantial fraction of alphas can be lost in one slowing down time. For B˜r/ B0〈10−4, the losses become insignificant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860061
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of ion diamagnetic flow on shock formation in poloidally rotating tokamak plasmas (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3596-3602 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: When the poloidal ion diamagnetic flow is of the order of the E×B drift velocity, it significantly affects the shock formation in a poloidally rotating tokamak plasma. (Here, E is the electric field and B is the magnetic field.) The poloidal density variation in both linear and shock regimes can be weakened if the poloidal ion diamagnetic flow tends to cancel the poloidal E×B flow. The magnitude of the density variation is not symmetric with respect to the direction of the E×B poloidal rotation. The resonant condition at which strong shock occurs is also modified dramatically by the diamagnetic flow. For some cases, the poloidal density variation inside the bifurcated electric field layer in the L–H transition [Phys. Rev. Lett. 42, 1408 (1982)] may not be large enough to significantly modify the plasma viscosity obtained by neglecting the compressibility effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860831
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