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  • 1
    Electronic Resource
    Electronic Resource
    Alfvén instabilities driven by circulating ions in optimized stellarators and their possible consequences in a Helias reactor (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 517-528 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work investigates circulating-particle-induced Alfvén instabilities in optimized stellarators of the Wendelstein line [F. Wagner, Trans. Fusion Tech. 33, 67 (1998)]. A general expression for the growth rate of the instabilities is obtained and analyzed. It is shown that the absence of the axial symmetry makes it possible that various types of Alfvén eigenmodes will be destabilized; both the kind of destabilized Alfvén eigenmodes and the type of the resonances driving the instability may differ from those in tokamaks. In particular, an important role of the helicity-induced resonance is predicted. The discovered new resonances may considerably increase the instability growth rate of both the "gap" modes and the eigenmodes residing below cylindrical Alfvén continuum. The upper limits of the local energy losses of circulating α-particles caused by various Alfvén instabilities in a four-period Helias reactor [C. D. Beidler et al., in Fusion Energy 2000, 18th International Atomic Energy Agency Conference Proceedings, Sorrento, 2000 (International Atomic Energy Agency, Vienna, 2001), Report IAEA-CN-77/FT/4] are evaluated. It is found that certain destabilized Alfvén eigenmodes will affect only alphas with the energy well below 3.5 MeV, which seems to open a possibility to remove the helium ash by exciting the corresponding Alfvén eigenmodes by either energetic particles or an antenna system. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1432993
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  • 2
    Electronic Resource
    Electronic Resource
    Interaction of neoclassical tearing modes with trapped fast ions (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 4834-4838 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Resonance between rotating neoclassical tearing mode (NTM) and precessing trapped energetic ions has been considered. Resonant ions experience large radial excursions of their banana guiding centers leading to the loss of a considerable fraction of fast ions deposited in the resonance region. The resulting toroidal torque accelerates the magnetic island rotating in the direction of the ion diamagnetic drift. The torque balance equation has been coupled with the modified Rutherford equation, retaining the contributions from the bootstrap current and the ion polarization current. It has been shown that, due to the resonant interaction with energetic ions, this autonomous system of equations exhibits a Hopf bifurcation for some critical ratio of the momentum damping rate to the resistive diffusion rate. The resulting stable limit cycle resembles the frequency jump events observed during NTM activity in the Axisymmetric Divertor Experiment Upgrade (ASDEX Upgrade) tokamak [S. Sesnic et al., Phys. Plasmas 7, 935 (2000)]. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1407283
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  • 3
    Electronic Resource
    Electronic Resource
    Theory of fast ion transport induced by sawtooth oscillations: Overview and new results (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2544-2554 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The work contains both an overview of recent theories and new results on the influence of sawtooth oscillations on the superthermal ions in a tokamak plasma. In particular, new results of numerical simulations of the sawtooth-crash-induced redistribution of fast ions are presented. The results are based on the approach suggested by the authors earlier [Nucl. Fusion 36, 159 (1996)]. Peculiarities of the particle motion during the crash are revealed. Dependence of the behavior of fast ions on their parameters, as well as on tokamak parameters and features of sawteeth, is analyzed. Based on this analysis, a simple picture showing the different effects of sawtooth oscillations on various groups of particles is suggested. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872233
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  • 4
    Electronic Resource
    Electronic Resource
    Alfvén continuum and high-frequency eigenmodes in optimized stellarators (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 491-509 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An equation of shear Alfvén eigenmodes (AE) in optimized stellarators of Wendelstein line (Helias configurations) is derived. The metric tensor coefficients, which are contained in this equation, are calculated analytically. Two numerical codes are developed: the first one, COBRA (COntinuum BRanches of Alfvén waves), is intended for the investigation of the structure of Alfvén continuum; the second, BOA (Branches Of Alfvén modes), solves the eigenvalue problem. The family of possible gaps in Alfvén continuum of a Helias configuration is obtained. It is predicted that there exist gaps which arise due to or are strongly affected by the variation of the shape of the plasma cross section along the large azimuth of the torus. In such gaps, discrete eigenmodes, namely, helicity-induced eigenmodes (HAE21) and mirror-induced eigenmodes (MAE) are found. It is shown that plasma inhomogeneity may suppress the AEs with a wide region of localization. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1339228
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  • 5
    Electronic Resource
    Electronic Resource
    Distributions of alpha particles escaping to the wall during sawtooth oscillations in the Tokamak Fusion Test Reactor (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1117-1130 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It has been observed experimentally in deuterium–tritium shots of the Tokamak Fusion Test Reactor (TFTR) [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)] that crashes of sawtooth oscillations may result in very inhomogeneous flux of alpha particles to the wall. To explain this phenomenon, both theoretical analysis and numerical simulation have been carried out. It is concluded that the "crash-induced prompt loss," i.e., the orbital loss of marginally trapped particles arising because of the crash-induced orbit transformation of circulating particles, is responsible for the flux near the bottom of the vessel, whereas the crash-induced stochastic diffusion of moderately trapped particles explains the large signal near the equatorial plane of the torus. The calculated poloidal distributions of the integral alpha flux are in reasonable agreement with experimental data. The energy spectrum of the escaping particles has also been calculated, which can be used for diagnostics of the crash type. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873358
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  • 6
    Electronic Resource
    Electronic Resource
    Resonant interaction of fast particles with neoclassical tearing modes (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 510-515 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cherenkov resonance between rotating neoclassical tearing mode (NTM) and energetic ions has been considered. Resonant interaction drives the current, which is in phase quadrature with the magnetic island and thus produces a toroidal torque accelerating island in the direction of the fast ion diamagnetic drift. This torque has been included in the coupled nonlinear first-order differential equations governing evolution of the NTM rotation frequency and amplitude. It has been shown that due to resonant interaction with energetic ions, this autonomous system exhibits Hopf bifurcation from the unstable stationary solution to the stable limit cycle describing nonlinear oscillations of the mode frequency and amplitude. Such behavior resembles the frequency jump events observed during NTM activity in ASDEX Upgrade [S. Guenter et al., Phys. Plasmas 7, 935 (2000)]. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1337616
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  • 7
    Electronic Resource
    Electronic Resource
    Superbanana orbits and redistribution of marginally trapped fast ions during sawtooth crashes (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 729-734 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The work represents the first step in studying the effect of sawtooth crashes on the "resonant" fast ions, i.e., the ions that are trapped or marginally untrapped with respect to the helical perturbation associated with the sawtooth crash. The simplest case is considered, when the particles in the absence of perturbations are marginally trapped in the tokamak magnetic field and characterized by narrow orbits. It is shown that in the presence of perturbation the guiding centers of the banana orbits oscillate in the toroidal and radial directions, forming "superbanana" orbits. The radial width of such "superbananas" constitutes a significant part of the sawtooth mixing radius, which implies that sawteeth can strongly redistribute these particles. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872759
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  • 8
    Electronic Resource
    Electronic Resource
    Theory of resonance influence of sawtooth crashes on ions with large orbit width (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2963-2976 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of resonances in the sawtooth-crash-induced redistribution of fast ions is investigated. In particular, the conditions of wave-particle resonant interaction in the presence of the equilibrium electric field and the mode rotation are obtained, and effects of sawteeth on the resonant particles with arbitrary width of nonperturbed orbits are studied. It is found that resonances play the dominant role in the transport of ions having sufficiently high energy. It is shown that the resonance regions may overlap, in which case the resonant particles may constitute the main fraction of the fast ion population in the sawtooth mixing region. The behavior of the resonant particles is studied both by constructing a Poincaré map and analytically, by means of the adiabatic invariant derived in this paper and calculation of the characteristic frequencies of the particle motion. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873021
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  • 9
    Electronic Resource
    Electronic Resource
    Reactivities of allyl bromides which are 3-cyclohexenyl compounds (1964)
    Springer
    Russian chemical bulletin 13 (1964), S. 1339-1344 
    Details
    ISSN: 1573-9171
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary 1. A study was made of the reactivity of allyl bromine in 3-cyclohexenyl compounds in various exchange reactions. 2. Allyl bromides of the 3-cyclohexenyl series in whose molecules the superannular effect is absent [5-bromo-1, 2-dimethyl-3-cyclohexene (i.e. 6-bromo-3,4-dimethylcyclohexene) and 4-(5-bromo-2-methyl-3-cyclohexen-l-yl)-3-buten-2-one] have the properties of ordinary allyl bromides, whereas in bromocyclohexenes in which superannular interaction is marked (5-bromo-2-methyl-3-cyclohexene-l-carboxaldehyde, methyl 5-bromo-2-mehtyl-3-cyclohexene-1-carboxaldehyde dimethyl acetal) the bromine is of low activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00850331
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  • 10
    Electronic Resource
    Electronic Resource
    Study of the rotational isomerism of the side chain of 3,5-disubstituted hydantoins (1987)
    Springer
    Chemistry of heterocyclic compounds 23 (1987), S. 282-283 
    Details
    ISSN: 1573-8353
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rotational isomerism of 3-alkyl(aryl)-5-alkyl(aralkyl)hydantoins in which the methylene group of the side chain, together with the methylidyne group in the 5 position of the ring, forms the structure of a substituted ethane was investigated by means of PMR spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00761984
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