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  • 1
    Electronic Resource
    Electronic Resource
    Ein Beitrag zum elektrischen Durschschlag im Vakuum (1966)
    Springer
    Electrical engineering 51 (1966), S. 101-109 
    Details
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Summary A hypothesis to explain the electrical breakdown in vacuum between metallic electrodes at room temperature is presented. Anode material is known to be transferred to the cathode in the pre-breakdown stage. It is postulated that this material piles up into points under the action of the electric field at the cathode to enhance this field considerably above its average value. The field emission current from these “emitting centres” heats the anode and luminous spots on the anode are observed. Breakdown occurs when the incident energy at any “anode spot” exceeds that which can be removed by conduction and radiation for example, thus resulting in the release of metal vapour. Experiments are presented in support of this hypothesis. A high voltage “post-breakdown discharge” is discussed, which is a self-sustaining flow of electron current from “emitting centres” limited only by the regulation of the supply.
    Notes: Übersicht Eine Hypothese zur Erklärung des elektrischen Durchschlags im Vakuum zwischen metallischen Elektroden bei Raumtemperatur wird angegeben. Es ist bekannt, daß Anodenmaterial im Vordurchbruchsstadium auf die Kathode übertragen wird. Es wird gefordert, daß dieses Material sich unter der Wirkung des elektrischen Feldes an der Kathode zu Spitzen formiert, um dieses Feld dort beträchtlich über seinem Mittelwert zu verstärken. Der Feldemissionsstrom von diesen “Emissionszentren” heizt die Anode auf, und leuchtende Flecken auf der Anode könne beobachtet werden. Der Durchschlag erfolgt, wenn die auftreffende Energie bei irgendeinem “Anodenfleck” das übrsteigt, was z. B. durch Wärmeableitung und Strahlung abgeführt werden kann, woraus ein Freiwerden von Metalldampf resultiert. Experimente werden angeführt zur Stützung dieser Hypothese. Eine Hochspannungs-“Nach-Durchschlagsentladung” wird diskutiert, die einen selbständigen Elektronenstrom von den “Emissionszentren” darstellt und nur begrenzt ist durch den Innenwiderstand der Stromversorgung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01407364
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  • 2
    Electronic Resource
    Electronic Resource
    Green's functions in WKB approximation (1991)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 1774-1779 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A systematic technique based on a variational principle is developed for obtaining WKB Green's functions for a non-Hermitian set of inhomogeneous, nonstationary differential equations in a space of arbitrary dimensions. A key element in this technique involves the use of the Van Vleck determinant for the amplitudes of WKB functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.529240
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  • 3
    Electronic Resource
    Electronic Resource
    Plasma Turbulence (1990)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 22 (1990), S. 317-347 
    Details
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.fl.22.010190.001533
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  • 4
    Electronic Resource
    Electronic Resource
    A fluid model for electron dynamics in the vacuum gap of a plasma opening switch (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 137-145 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-dimensional fluid model is developed to study the equilibrium flow of electrons in the vacuum gap between the cathode and the plasma of a plasma opening switch. The dynamics of electron flow in the vacuum gap region is illustrated by the distributions of the magnetic field, the electrostatic potential, and the electron density. The dependencies of the switch current and its interruption in the vacuum gap on the dimensions of the vacuum gap, the load impedance, and the electrostatic potential across the gap are investigated. The two-dimensional aspect of the electron flow in the vacuum gap and its effects on the performance of a plasma opening switch are emphasized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347749
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  • 5
    Electronic Resource
    Electronic Resource
    One-dimensional intense laser pulse solitons in a plasma (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1489-1491 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A general analytical framework is developed for the nonlinear dispersion relations of a class of large amplitude one-dimensional isolated envelope solitons for modulated light pulse coupled to electron plasma waves, previously investigated numerically [Kozlov et al., Zh. Eksp. Teor. Fiz. 76, 148 (1979); Kaw et al., Phys. Rev. Lett. 68, 3172 (1992)]. The analytical treatment of weakly nonlinear solitons [Kuehl and Zhang, Phys. Rev. E 48, 1316 (1993)] is extended to the strongly nonlinear limit. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872346
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  • 6
    Electronic Resource
    Electronic Resource
    Current neutralization and focusing of intense ion beams with a plasma-filled solenoidal lens. I (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 4725-4739 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The response of the magnetized plasma in an axisymmetric, plasma-filled, solenoidal magnetic lens, to intense light ion beam injection is studied. The lens plasma fill is modeled as an inertialess, resistive, electron magnetohydrodynamic (EMHD) fluid since characteristic beam times τ satisfy 2π/ωpe,2π/Ωe(very-much-less-than)τ≤2π/Ωi (ωpe is the electron plasma frequency and Ωe,i are the electron, ion gyrofrequencies). When the electron collisionality satisfies νe(very-much-less-than)Ωe, the linear plasma response is determined by whistler wave dynamics. In this case, current neutralization of the beam is reduced on the time scale for whistler wave transit across the beam. The transit time is inversely proportional to the electron density and proportional to the angle of incidence of the beam with respect to the applied solenoidal field. In the collisional regime (νe〉Ωe) the plasma return currents decay on the normal diffusive time scale determined by the conductivity. The analysis is supported by two-and-one-half dimensional hybrid particle-in-cell simulations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872040
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  • 7
    Electronic Resource
    Electronic Resource
    A study of the magnetic compression of energetic ion layers in conductive plasmas (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1783-1791 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results of a study of the magnetic compression of one-dimensional energetic ion layers in the presence of conductive background plasmas in cylindrical geometry are presented. For this, an updated hybrid (particle-ion and fluid-electron) computer model has been used. The first observation is that when the magnetic field at the wall is ramped quickly relative to the radial Alfvén wave transit time across the cylinder then a magnetic probe on axis would measure a larger field perturbation. When the wall field is ramped slowly, the layer energy increases proportionally with the external magnetic-field strength and, as expected, the layer self-field on axis does not change relative to external field. A study is also made of the effects of transient fluctuations on the layer energy when the field is ramped quickly. When the ramped field strength is small compared with the ambient field (the linear case), the average layer kinetic energy gained is not substantially different from the case where ramping is slow; however, the fluctuating energy is more than twice the average change. The interesting observation is made that the thermal spread in particle energy for a layer is not necessarily related to the strength of the self-field. This is explained in terms of the single particle motion in a self-potential well, and is different from the expected result for a two-dimensional ring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870685
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  • 8
    Electronic Resource
    Electronic Resource
    Conventional solar flare theory re-examined : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1929-1935 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Major objections are raised to the fundamental paradigm underlying conventional solar flare theory, viz., that the required free energy can be stored in situ at the requisite density in the corona in nonpotential magnetic fields by the action of photospheric convective motion, that it can be released rapidly through magnetic reconnection by a triggering event, and that a significant fraction of this energy is converted to x rays. An alternative explanation that avoids these difficulties requires that magnetic energy in the form of strongly sheared flux tubes be stored subphotospherically prior to the flare. It is the emergence of this subphotospherically stored magnetic shear energy into the photosphere and above, and its rapid conversion through internal magnetic reconnection to other forms that constitutes an actual flare. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872572
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  • 9
    Electronic Resource
    Electronic Resource
    Formation of field-reversed ion rings in a magnetized background plasma (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2773-2783 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In typical field-reversed ion ring experiments, an intense annular ion beam is injected across a magnetic cusp into neutral gas immersed in a solenoidal magnetic field. In anticipation of a new experimental thrust to create strong field-reversed ion rings the beam evolution is investigated in a preformed background plasma on a time scale greater than an ion cyclotron period, using a new two and a half-dimensional (21/2-D) hybrid, particle-in-cell (PIC) code FIRE, in which the beam and background ions are treated as macro-particles and the electrons as a massless fluid. It is shown that under appropriate conditions axial beam bunching occurs in the downstream applied field and a compact field-reversed ring is formed. It is observed that the ring is reflected in a ramped magnetic field. Upon reflection its axial velocity is very much less than that expected from a single particle model due to the transfer of the mean axial momentum to the background ions. This increases the time available to apply a pulsed mirror for trapping the ring experimentally. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871175
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  • 10
    Electronic Resource
    Electronic Resource
    Small scale magnetic flux-averaged magnetohydrodynamics (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 2488-2514 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By relaxing exact magnetic flux conservation below a scale λ a system of flux-averaged magnetohydrodynamic equations are derived from Hamilton's principle with modified constraints. An energy principle can be derived from the linearized averaged system because the total system energy is conserved. This energy principle is employed to treat the resistive tearing instability and the exact growth rate is recovered when λ is identified with the resistive skin depth. A necessary and sufficient stability criteria of the tearing instability with line tying at the ends for solar coronal loops is also obtained. The method is extended to both spatial and temporal averaging in Hamilton's principle. The resulting system of equations not only allows flux reconnection but introduces irreversibility for appropriate choice of the averaging function. Except for boundary contributions which are modified by the time averaging process total energy and momentum are conserved over times much longer than the averaging time τ but not for less than τ. These modified boundary contributions correspond to the existence, also, of damped waves and shock waves in this theory. Time and space averaging is applied to electron magnetohydrodynamics and in one-dimensional geometry predicts solitons and shocks in different limits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870577
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