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  • 1
    Electronic Resource
    Electronic Resource
    Emission properties of different cathodes at E≤105 V/cm (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2379-2399 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present results of the investigation of different types of cathodes operating in an electron diode powered by a high-voltage generator (300 kV, 250 ns, 84 Ω, ≤5 Hz). The cathodes which have the same emitting area of 100 cm2 are made of metal–ceramic, carbon fibers, carbon fabric, velvet, or corduroy. We also tested carbon fibers and carbon fabric cathodes coated by CsI. It was shown that for all types of cathodes the electron emission occurs from the plasma which is formed as a result of a flashover of separate emitting centers. The amount of the emitting centers and the time delay in the electron emission were found to depend strongly on the accelerating electric field growth rate. Experimental data concerning the uniformity of the light emission from the cathode surface and divergence of the generated electron beams are presented. Data related to the general parameters of the diode, namely its impedance, power, and energy are given as well. For all the cathodes investigated the observed diode impedance indicated the existence of a quasistationary cathode plasma boundary for electron current density ≤20 A/cm2. We present the dependencies of the average emitted electron current density and of the time delay in the electron emission on the number of generator shots. We also present data of the vacuum deterioration as a result of the tested cathodes operation. The obtained data are discussed within the framework of plasma formation as a result of cathode surface flashover. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1337924
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  • 2
    Electronic Resource
    Electronic Resource
    Plasma sources for high-current electron beam generation : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2466-2472 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A review of experimental studies of the operation of cathodes made of metal-ceramic, velvet, corduroy, carbon fibers, carbon fabric, and different types of ferroelectrics is presented. These cathodes operated at electric fields in the range of 5–60 kV/cm that allowed the generation of electron beams with duration of several hundreds of nanoseconds while keeping a quasi-constant diode impedance. All cathodes had the same diameter and were tested in a diode powered by a high-voltage generator (300 kV, 85 Ω, 250 ns, ≤5 Hz). It was shown that the source of electrons for all the studied cathodes is a plasma which is formed as a result of surface discharges. Different types of electrical and optical diagnostics were used to study the formation and parameters of the plasma, the potential distribution inside the anode–cathode gap, and the uniformity and divergence of the extracted electron beam as a function of the amplitude and rise time of the accelerating pulse. Results of the lifetime of the tested cathodes and their compatibility with vacuum requirements are presented as well. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1345503
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  • 3
    Electronic Resource
    Electronic Resource
    Plasma-assisted electron emission from (Pb,La)(Zr,Ti)O3 ceramic cathodes (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3669-3674 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strong pulsed electron emission has been observed from 12/65/35 lead lanthanum zirconate titanate ceramic composition in two different nonswitched phases at room temperature and at the temperature 100 °C. The electron emission parameters of this composition appear to be independent of phase for the two phases investigated. Fast photography and direct observation show that the strong electron emission occurs from the surface discharge plasma. The new experimental data make it possible to demonstrate the validity of the Child–Langmuir law for this electron emitter. A pulsed plasma lead lanthanum zirconate titanate ceramic cathode with burst frequency up to 100 kHz and collector current density up to 10 A/cm2 is developed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361196
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  • 4
    Electronic Resource
    Electronic Resource
    Copious electron emission from triglycine sulfate ferroelectric crystals (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2248-2252 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown experimentally that the electron charge emitted from triglycine sulfate pulse ferroelectric cathodes can be as large as 129 μC/cm2. This charge considerably exceeds the measured value of spontaneous polarization, Ps=2.8 μC/cm2. A bipolar voltage is found to facilitate the appearance of the electron emission. It is proposed that the source of the emission current is the plasma of uncompleted surface discharges. This plasma is initiated at the metal-vacuum-dielectric triple points both by the field electron emission and the electron emission stimulated by polarization switching. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360758
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  • 5
    Electronic Resource
    Electronic Resource
    Spectroscopic investigations of the plasma behavior in a plasma opening switch experiment (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2122-2137 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron density, the electron kinetic energy, the particle motion, and electric fields in a coaxial positive-polarity plasma opening switch (POS) were studied using spectroscopic diagnostics. A gaseous source that injects the plasma radially outward from inside the inner POS electrode was developed. The plasma was locally seeded with various species, desired for the various measurements allowing for axial, radial, and azimuthal resolutions both prior to and during the 180 ns long current pulse. The electron density was determined from particle ionization times and the electron energy from line intensities and time dependent collisional-radiative calculations. Fluctuating electric fields were studied from Stark broadening. The ion velocity distributions were obtained from emission-line Doppler broadenings and shifts. The early ion motion, the relatively low ion velocities and the nearly linear velocity dependence on the ion charge-to-mass ratio, leads to the conclusion that the magnetic field penetrates the plasma early in the pulse. The ion velocity dependence on the axial location were thus used to infer the time dependent axial distribution of the magnetic field, indicating the formation of a relatively high current density at the load-side edge of the plasma. This is expected to cause plasma acceleration towards the load, found to be supported by charge-collector measurements. The fast magnetic field penetration could be explained by mechanisms based on the Hall effect. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871299
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  • 6
    Electronic Resource
    Electronic Resource
    Spectroscopic investigation of fast (ns) magnetic field penetration in a plasma (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2583-2589 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The time-dependent magnetic field spatial distribution in a coaxial positive-polarity plasma opening switch (POS) carrying a current (approximately-equal-to)135 kA during (approximately-equal-to)100 ns, was investigated by two methods. In the first, ionic line emission was observed simultaneously for two polarizations to yield the Doppler and Zeeman contributions to the line profiles. In the second method, the axial velocity distribution of ions was determined, giving the magnetic field through the ion equation of motion. This method requires knowledge of the electron density, here obtained from the observed particle ionization times. To this end, a lower bound for the electron kinetic energy was determined using various line intensities and time-dependent collisional-radiative calculations. An important necessity for POS studies is the locality of all measurements in r, z, and θ. This was achieved by using laser evaporation to seed the plasma nonperturbingly with the species desired for the various measurements. The Zeeman splitting and the ion motion showed magnetic field penetration through the 3.5 cm long plasma at a velocity (approximately-equal-to)108 cm/s. The current density was found to be relatively high at the load-side edge of the switch plasma. It is suggested that this may cause plasma acceleration into the vacuum section toward the load, which is supported by charge-collector measurements. The fast magnetic field penetration agrees with estimates based on the Hall-field mechanism. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871220
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  • 7
    Electronic Resource
    Electronic Resource
    Observation of downstream energetic electron/ion flow and accompanied high-power microwave radiation during the opening of a submicrosecond plasma opening switch (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 686-695 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, results of experimental investigations of high-energy electron beam generation and transportation in the region downstream of a submicrosecond plasma opening switch (POS) (Ipos ≤35 kA, τ1/4≅300 ns) are presented. This electron beam is accompanied by collectively accelerated ions having energies several times higher than the electron energies. Experiments were carried out with different loads: short-circuit, high-impedance, and planar electron diode. It is shown that the electron/ion beam appearance in the region downstream of the POS load occurs almost simultaneously with the beginning of the inductive voltage, independently of the type of load. In addition, generation of high-power microwave radiation (fmw ≤10 GHz, Pmw≤200 MW) was observed for all types of loads. We believe that the generation of the microwave radiation is related to the injection of a noncomplete charge-neutralized electron beam into the downstream drift region. These results and a qualitative explanation of the generation of the inductive voltage and microwave radiation are discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369148
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  • 8
    Electronic Resource
    Electronic Resource
    Formation of discharge plasma on the surface of cathodes with different dielectric constants (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7946-7951 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a detailed study of the spatial and temporal evolution of visible light emission from plasma formed on the surface of ferroelectrics [Pb(Zr,Ti)O3 and BaTiO3] and a printed-circuit board under the application of a high-voltage pulse. For all samples studied, plasma formation occurs within the first 5 ns from the start of the high-voltage pulse. It is shown that the plasma appears at the edges of the front strip electrodes. Further, the plasma spreads along the dielectric surface covering it partially. It is found that the uniformity of the plasma and the distance of its propagation along the surface depend on the properties of the dielectric, the polarity and amplitude of the high-voltage pulse, and the vacuum conditions. A qualitative model which explains the observed experimental data is suggested. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370613
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  • 9
    Electronic Resource
    Electronic Resource
    Electron energy and potential distribution in a diode with a ferroelectric cathode (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3270-3278 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the time and space resolved energy of charged particles emitted from the plasma formed on the surface of polarized and unpolarized ferroelectric cathodes under the application of driving pulses having either a positive or negative polarity. It is found that the energy of the emitted charged particles does not exceed the amplitude of the driving voltage and is independent of the initial polarization state of the ferroelectric. In addition, data concerning the energy of the electrons under the application of an accelerating pulse of 25 kV, and data concerning the electron beam uniformity and the time resolved potential distribution inside the anode–cathode gap of the electron diode are presented. We discuss our experimental results within the framework of the incomplete surface discharge model. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372335
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  • 10
    Electronic Resource
    Electronic Resource
    Comment on "Mixed electron emission from lead zirconate–titanate ceramics" [J. Appl. Phys. 83, 6055 (1998)] (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 8495-8496 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Understanding the mechanism responsible for electron emission from ferroelectrics is crucial for the design of ferroelectric cathodes. The mixed process suggested in the model of Zhang et al. [J. Appl. Phys. 83, 6055 (1998)] appears to contain some contradictions. The most problematic is the coexistence of two electron emission processes on the same surface in different electric fields. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370697
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