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  • 1
    Electronic Resource
    Electronic Resource
    Three-fluid simulation of the plasma-erosion-opening switch (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4208-4211 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamics of the plasma-erosion-opening switch is characterized with the aid of 2D three-fluid simulation using the anthem implicit simulation code, for plasma fill densities ranging from 1012 to 6×1013 cm−3 with 45-ns pulse rise times. The switch behavior is found to depend sensitively on the threshold for electron emission at the cathode, on the detailed structure of the anode with its injection holes, and on the possible action of anomalous resistivity in the fill plasma. Closest agreement with NRL GAMBLE I experimental results is obtained with the combination of zero electric field threshold emission at the cathode, an "open'' anode, and modest anomalous resistivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341336
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  • 2
    Electronic Resource
    Electronic Resource
    Relaxation mechanism of ferroelectric switching in Pb(Zr,Ti)O3 thin films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2332-2336 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The polarization reversal process of tetragonal Pb(Zr,Ti)O3 thin films has been intensively studied using conventional hysteresis and rectangle pulse measurements. Decreasing the voltage level of the pulses significantly slows down the polarization switching to the range of milliseconds. The switching current response shows a Curie–von Schweidler behavior over a broad time range. The transient current and the frequency dependence of the P–V loops of these films compared to the properties of ferroelectric single crystals show some similarities but also significant differences. The theoretical models of the classical ferroelectric phase transition and especially the conditions of the pulse measurements in single crystals and thin films are discussed. It leads to the conclusion that it is not the domain wall structure and domain wall motion that determine the polarization reversal but dissipative polarization processes which can take place in both ferroelectric and nonferroelectric high-k dielectric thin films. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1331341
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  • 3
    Electronic Resource
    Electronic Resource
    Highly charged ions produced in a warm electron beam ion trap : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 690-692 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact electron beam ion trap (WEBIT) working at room temperature without any cryogenic components is described and experimentally investigated. The trap design is based on permanent magnet technology. For the formation of the electron beam a Pierce electron gun equipped with a cathode of high emissivity is used. The ion trap is created by a compressed electron beam passing through a drift tube system consisting of three sections with corresponding electrical trap potentials. X-ray spectra measured with a Si(Li) semiconductor detector indicate the production of Kr34+, Xe44+, Ce48+, Ir64+, and Hg66+ ions. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150262
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  • 4
    Electronic Resource
    Electronic Resource
    A semiclassical approach to dissipation in quantum mechanics (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 3696-3704 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Employing the path integral formalism, we study a quantum (test) system coupled to an environment consisting of infinitely many harmonic oscillators. A simple semiclassical approxi- mation, in which only real classical trajectories are required, is used to derive the propagator of the reduced density matrix for Ohmic dissipation and high temperatures. The inclusion of a summation over trajectories with the correct Maslov phases in the final expression for the propagator permits investigation of nonharmonic test systems. In a numerical example for a Morse oscillator interacting with a high temperature heat bath, the semiclassical result, obtained by the method described here, correctly displays the suppression of quantum behavior as observed in the exact calculation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470046
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  • 5
    Electronic Resource
    Electronic Resource
    Homogeneous and inhomogeneous linewidths of excitons in partially ordered Ga0.52In0.48P (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2347-2349 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report picosecond four-wave mixing experiments on Ga0.52In0.48P grown by organometallic vapor phase epitaxy on GaAs substrates. The spectral behavior of the homogeneous linewidth in the range of the inhomogeneously broadened band gap excitonic resonance is found to be different for a more disordered as compared to a partially ordered structure. Whereas the former shows the normal alloy behavior, the behavior of the partially ordered sample supports the assumption that its structure consists of ordered domains with varying degrees of order. This means, in particular, that the main origin of the inhomogeneous broadening is different for the disordered and ordered case. In addition, a polarization dependence of the four-wave mixing signal is only observed for the more disordered sample. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112742
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  • 6
    Electronic Resource
    Electronic Resource
    Power flow between a plasma-opening switch and a load separated by a high-inductance magnetically insulated transmission line (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2648-2656 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results are presented from particle-in-cell simulations of the electron flow launched from a plasma opening switch (POS) into a magnetically insulated transmission line (MITL) as the POS opens. The opening process of the POS is treated by removing plasma from a fixed anode-cathode gap with an opening time of τrise. To be similar to opening switch experiments at Physics International, the simulations were performed with the same inductance LMITL between the POS and load. When LMITL/τrise is large compared to the POS flow impedance, this inductance effectively isolates the POS from the load during the opening process and the POS voltage is insensitive to changes in the load impedance. Analysis and simulations show that the peak load power is maximized when the load impedance is equal to the POS flow impedance. In contrast to previous theories and simulations of magnetically insulated flows, a large amount of electron flow in the MITL is concentrated near the anode. This is a result of the high effective impedance imposed on the POS by the inductive load which causes a significant electron current loss in the POS. As a result, many electrons lose insulation on the load side of the POS gap and those that do flow into the MITL have been accelerated to nearly the full POS potential. Electrons then E×B drift on equipotential lines close to the anode as they enter the MITL and flow toward the load. Current losses in the MITL are observed due to the proximity of the electron flow to the anode. Some electrons flow from the MITL directly into the load and are registered as load current while others E×B drift back toward the POS along the cathode surface. This is possible because the electron flow launched into the MITL from the POS is large enough to cause sufficient positive image charges on the cathode so that the electric field points out of the cathode surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358506
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  • 7
    Electronic Resource
    Electronic Resource
    Charged particle flow in plasma-filled pinched-electron-beam diodes (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2274-2286 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma-filled pinched-electron-beam diode experiments have been performed on the Gamble II (1.5 MV, 800 kA, 60 ns) pulsed power generator at Naval Research Laboratory. These plasma-filled diode (PFD) experiments show three phases of behavior: a low impedance phase followed by a phase of rapidly increasing impedance that culminates in a relatively constant vacuum impedance phase. The duration of the low impedance phase as well as the final operating impedance depends on the prefill plasma density. The charged particle flow in the PFD is studied with one-dimensional (1-D) and two-dimensional (2-D) simulation models. These simulation models show the formation of growing sheaths at both electrodes during the low impedance phase. The end of the low impedance phase in the simulations coincides with the two sheaths meeting in the center of the anode-cathode (A-K) gap. Based on these observations, an analytic model was developed that treats the low impedance phase as symmetric bipolar sheaths. The analytical model adequately predicts the duration of the low impedance phase predicted by the 1-D simulation model. Differences between the bipolar model and the experiments or 2-D simulations can be explained in terms of magnetized sheaths which enhance the ion current over the bipolar level and cause the sheath to grow faster than the bipolar model. During the rapidly increasing impedance phase, the simulations show that the cathode sheath quickly expands to completely fill the A-K gap. At this time, charged particle flow in the simulation models are consistent with the vacuum gap spacing. Experimentally, the higher density, longer conduction time, PFD shots exhibited a significantly lower final impedances than predicted by 2-D simulations. This difference is probably caused by expanding electrode surface plasmas produced by the interaction of the plasma source with one or both electrode surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354711
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  • 8
    Electronic Resource
    Electronic Resource
    Current channel migration and magnetic field penetration in a perfectly conducting plasma with emitting, conducting boundaries (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2307-2314 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In collisionless simulations of the plasma erosion opening switch, a highly conductive plasma allows magnetic field penetration through the entire length of the plasma, to depths almost two orders of magnitude greater than the collisionless skin depth, c/ωpe. Field penetration is accomplished by a narrow (skin-depth-like) current channel that migrates through the plasma. The plasma behind the current channel is unable to shield the rising magnetic field from the body of the plasma and allows it to penetrate almost instantly and completely through the plasma up to the current channel. The migration of the channel and the penetration of the field appear to occur in the absence of both Coulomb collisions and instabilities. These unusual features are permitted by the electric field structure in the plasma behind the current channel and the presence of conducting boundaries that can emit electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344287
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  • 9
    Electronic Resource
    Electronic Resource
    A new theory of the plasma-filled diode (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2168-2180 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The behavior of a planar plasma-filled diode (PFD) is examined in the limit in which the mass of the plasma ions is allowed to approach infinity. In this limit the plasma ions are immobilized and act as a fixed, spatially uniform background of positive charge. Using a one-dimensional, electrostatic particle-in-cell simulation of a PFD coupled to an external LC circuit, it is shown that the PFD still has a low-voltage conduction phase followed by a high-voltage opening phase in this limiting case. An analytic theory is developed that describes the operation of the diode in the immobile ion case, and this theory is shown to be in good agreement with the simulation results. A simple expression is also derived that gives an upper bound on the current that may be conducted before opening as a function of the density of immobile ions. Finally, it is shown that essentially the same process that determines the behavior of the PFD in the immobile ion limit also controls the operation of the PFD in the case where the ions have finite mass and are free to move under the influence of the diode electric fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351113
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  • 10
    Electronic Resource
    Electronic Resource
    Particle-in-cell simulations of fast magnetic field penetration into plasmas due to the Hall electric field (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3556-3563 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Particle-in-cell (PIC) simulations are used to study the penetration of magnetic field into plasmas in the electron-magnetohydrodynamic (EMHD) regime. These simulations represent the first definitive verification of EMHD with a PIC code. When ions are immobile, the PIC results reproduce many aspects of fluid treatments of the problem. However, the PIC results show a speed of penetration that is between 10% and 50% slower than predicted by one-dimensional fluid treatments. In addition, the PIC simulations show the formation of vortices in the electron flow behind the EMHD shock front. The size of these vortices is on the order of the collisionless electron skin depth and is closely coupled to the effects of electron inertia. An energy analysis shows that one-half the energy entering the plasma is stored as magnetic field energy while the other half is shared between internal plasma energy (thermal motion and electron vortices) and electron kinetic energy loss from the volume to the boundaries. The amount of internal plasma energy saturates after an initial transient phase so that late in time the rate that magnetic energy increases in the plasma is the same as the rate at which kinetic energy flows out through the boundaries. When ions are mobile it is observed that axial magnetic field penetration is followed by localized thinning in the ion density. The density thinning is produced by the large electrostatic fields that exist inside the electron vortices which act to reduce the space-charge imbalance necessary to support the vortices. This mechanism may play a role during the opening process of a plasma opening switch. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871946
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