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  • 1
    Electronic Resource
    Electronic Resource
    The influence of the spectral properties of electrostatic fluctuations on the ambipolar electric field and plasma rotation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3667-3675 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A general system of momentum balance equations that take into account neoclassical effects and the fluctuations of plasma quantities and electromagnetic field is established. This is used to study the influence of the properties of electrostatic fluctuations on the radial anomalous flows and ambipolar electric field. The case when the momentum drag is provided by collisions with neutrals is considered, which is relevant for the edge plasma. It is shown that a change of the spectrum accompanied by a transfer of 40% of the fluctuation energy from the big wavelength region to the small wavelength region of the spectrum can lead to a change of up to 20% in the magnitude of the electric field. As a result the plasma rotation will change. The possibility to induce plasma spin-up through the ambipolar electric field produced by monochromatic waves delivered from an external source is also considered. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871066
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  • 2
    Electronic Resource
    Electronic Resource
    Diffusion of charged particles in tokamak-like stochastic magnetic and electric fields (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 3935-3951 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper the diffusion of guiding centers induced by stochastic magnetic and electric field fluctuations, with both time and space dependence, is analyzed for the case of tokamak plasmas. General experimental results on tokamak fluctuations are used to derive guiding-center equations that properly describe the particle motion. These equations assume uniform average magnetic and electric fields with random stationary Gaussian fluctuations that constitute a homogeneous and cylindrically symmetric turbulence. By applying Novikov's theorem, a Fokker–Planck equation for the probability distribution function is derived and an expression for the guiding-center diffusion coefficient is obtained. This coefficient not only contains the standard terms due to the stochastic wandering of the magnetic lines and the stochastic electric drift, but also new terms due to the stochastic curvature and ∇B drifts. The form of these terms is shown explicitly in terms of the correlation functions of the fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860349
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  • 3
    Electronic Resource
    Electronic Resource
    Evolution of the plasma rotation and the radial electric field for a toroidal plasma in the Pfirsch–Schlüter and plateau regimes subject to a biased electrode (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1200-1212 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper, the fluid equation approach is used to analyze the time evolution of the plasma rotation and the ambipolar electric field in a nonsymmetric toroidal plasma subject to an external biasing voltage induced by a probe. Under consideration is a plasma with low rotation speed in the Pfirsch–Schlüter or the plateau regime that includes the effects of a background neutral gas. A time-dependent charge conservation equation is used to determine the ambipolar electric field as a function of time. It is found that, after the application of the biasing voltage, the electric field and the plasma rotation change quickly and reach steady-state after a time inversely proportional to the sum of the momentum damping rates due to parallel viscosity and ion–neutral collisions. The steady state is characterized by a radial electric field and a plasma rotation that are proportional to the electric current flowing through the biasing probe. The direction of the plasma flow is determined by the relative magnitude of the momentum damping rates on the flux surface. From the steady-state solution, an expression for the radial electric conductivity is obtained, which includes the effect of collisions with neutrals as well as viscosity. Axisymmetric systems without neutrals are also discussed, which is a special case since there is no momentum damping in the toroidal direction. Here, the toroidal velocity increases continuously in time with the bias and never reaches steady state. Finally, a model for nonsymmetric magnetic fields is presented and the viscous damping rate, the radial conductivity and the spin-up rate for a plasma in the Pfirsch–Schlüter regime are calculated. As examples, the cases of the rippled tokamak and the classical and helically symmetric stellarators are evaluated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860910
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  • 4
    Electronic Resource
    Electronic Resource
    Parallel and toroidal viscosity for nonaxisymmetric toroidal plasmas in the plateau regime (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 527-530 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Calculations of the viscosity expressions appearing in the fluid approach to neoclassical transport of nonaxisymmetric toroidal plasmas are presented. By assuming the Chew–Goldberger–Low form for the viscosity tensor and a large-aspect-ratio plasma, the drift kinetic equation for the plateau regime is solved and expressions for the parallel and toroidal viscosity are calculated as functions of plasma and heat fluxes. The viscosity expressions found for the plateau regime are similar to the expressions valid in the collision-dominated regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865440
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  • 5
    Electronic Resource
    Electronic Resource
    On the definition of Pfirsch–Schlüter and bootstrap currents in toroidal systems (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1294-1300 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the plasma physics literature there appear two different definitions of Pfirsch–Schlüter current. One of them is predominantly used in equilibrium calculations and satisfies the condition IT=0. The other definition appears commonly in transport calculations and requires that the surface average of the dot product of the Pfirsch–Schlüter current density with the magnetic field vanish, i.e., 〈JPS⋅B〉=0. The difference between the definitions is a surface function. Within the framework of the moment equation approach, the total parallel current is completely determined through a surface average of Ohm's law; thus different definitions of Pfirsch–Schlüter current imply different expressions for the bootstrap current. Understanding the different implications of these two definitions is of particular importance when designing toroidal devices with minimized Pfirsch–Schlüter current or studying tokamaks with optimized bootstrap current. In this paper the definitions of Pfirsch–Schlüter and bootstrap current, as well as the expressions for the corresponding Pfirsch–Schlüter diffusion flux, are analyzed and discussed for the case of axisymmetric and nonaxisymmetric plasmas. Although in cases like a current-free stellarator or a large-aspect-ratio tokamak both definitions are equivalent, they are in general different, and in order to avoid misunderstandings it is therefore important to use only one. The most appropriate definition is IT=0. In this paper the equations for determining the bootstrap current within the framework of the fluid equations are also analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860085
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  • 6
    Electronic Resource
    Electronic Resource
    Calculation of Hamada coordinates for a large-aspect-ratio tokamak (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 530-535 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The application of the well-known moment equation approach to neoclassical transport requires the use of Hamada coordinates in three-dimensional toroidal plasmas. The lack of analytical expressions and the difficulty associated with the numerical calculation of these coordinates has strongly limited the use of this approach. In this paper analytical calculations of Hamada coordinates for a large-aspect-ratio tokamak are presented. Knowledge of these coordinates for this relatively simple two-dimensional case will allow, for the first time, a general analytical application of the moment equation approach, and also a check of this approach against well-known results. In particular, it is shown here that the approach correctly reproduces the Pfirsch–Schlüter diffusion rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859343
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  • 7
    Electronic Resource
    Electronic Resource
    The ambipolar electric field and neoclassical heat and particle flows in nonaxisymmetric toroidal multispecies plasmas with sources (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 3171-3179 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fluid description of neoclassical transport theory is applied to a general nonaxisymmetric toroidal multispecies plasma with sources. From moment equations, expressions for plasma rotation, electric current, radial heat and particle transport fluxes, and ambipolar electric field are obtained. These expressions are valid in both the plateau and collision-dominated regimes. The effect of momentum and energy flux sources on particle and heat flows, electric current, radial transport fluxes, and on the ambipolar electric field is explicitly shown. In these calculations radial temperature gradients are taken into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866492
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of maternal light environment on germination and morphological characteristics of Sicyos deppei seeds (2000)
    Oxford UK : Blackwell Science Ltd
    Weed research 40 (2000), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effect was studied of sunlight and far-red (FR) light during seed development, on seed quality and germination of Sicyos deppei G. Don. Seeds exposed to FR during development were lighter in colour and their weight, size and water content were significantly lower. Less than 10% of non-scarified freshly harvested seeds germinated. Scarified, freshly harvested seeds developed under sunlight had a partially negative photoblastic response; both red (R) and FR light inhibited germination. The highest and fastest germination occurred in darkness, probably due to the effect of the high photon flux densities on the phytochrome during seed development. Scarified seeds ripened under FR light, germinated well in FR light and in darkness, but R light inhibited germination. After 6 months of storage, the permeability of S. deppei seeds increased, the partially negative photoblastic response was lost and germination of scarified seeds increased. Specifically, in seeds developed under FR, germination in darkness was faster than for the other light treatments, but slow in darkness for seeds developed under sunlight. The physiological and morphological heteroblastic responses in S. deppei probably extend its seed germination and seedling recruitment periods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.2000.00206.x
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  • 9
    Electronic Resource
    Electronic Resource
    Non-equilibrium fluctuations of a Rayleigh particle in a two-component gas
    Amsterdam : Elsevier
    Physica A: Statistical Mechanics and its Applications 157 (1989), S. 1180-1194 
    Details
    ISSN: 0378-4371
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0378-4371(89)90038-1
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  • 10
    Electronic Resource
    Electronic Resource
    Statistical study of the muon catalyzed d-t fusion cycle (1995)
    Springer
    Hyperfine interactions 96 (1995), S. 139-151 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper we discuss the statistics of the main branch species of the muon catalyzed d-t fusion. From a master equation we derive and numerically solve kinetic equations for the average density and the covariances of a system composed of muons, muonic deuterium and muonic tritium atoms, muon molecular d-t ions, muonic helium, helium and neutrons. The system consists of an initial fixed amount of muons in a 50–50% D2 + T2 mixture without any external muon source. It is known that the probability distribution function of the population species with the exception of the neutron and helium follow a multinomial distribution function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02066278
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