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  • 1
    Electronic Resource
    Electronic Resource
    The bottleneck in pseudospark discharges (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 625-630 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Physical mechanisms during early phases of pseudospark discharges are still under discussion. Experiments at low rates of current rise (dI/dt〈109 A/s) were performed to investigate these phenomena, using filtered fast shutter photography of the discharge plasma in the visible wavelength region. Additionally temporally resolved measurements of line emission of the filling gas (hydrogen and helium) and cathode material (copper) were performed. These experiments revealed a discharge phase where the cathode surface involved in the discharge is restricted mainly to the inside of the cathode aperture. The voltage drop during that phase is about 200–400 V and the current density exceeds 1 kA/cm2. A possible explanation of the discharge mechanisms during that discharge phase is self-sputtering of cathode material from the cathode surface inside the cathode aperture. The described mechanisms might be fundamental for the transition from the transient hollow cathode phase to the high current phase in pseudospark discharges. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362663
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  • 2
    Electronic Resource
    Electronic Resource
    First experimental observation of the ignition of a "superdense glow'' before the glow-to-arc transition in a pseudospark discharge (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 631-636 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The presented results are the first experimental indication for the existence of a homogeneous superdense glow in the bore hole of the cathode in a pseudospark discharge. The start of this mechanism is leading to the low-impedance high-current phase and starts before the glow-to-arc transition in the pseudospark discharge. It is assumed that the high-current density is carried mainly by metal ions which originate from a self-sustained self-sputtering mechanism, or by a large number of, on a macroscopic scale, homogeneously distributed Schottky emitters. It is shown that the geometric features of the bore hole cause an enhancement of this effect. These results and the theoretical assumptions can also explain very effectively the current quenching of the pseudospark discharge. Current quenching is only occurring during the superdense glow when no cathode spots are ignited. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360805
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  • 3
    Electronic Resource
    Electronic Resource
    Simulation of Z-pinch dynamics in a high-current plasma lens with a new one-dimensional model including finite plasma conductivity (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 922-926 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamics of a fast Z-pinch plasma lens was simulated with a one-dimensional model for the phase of constriction. The calculation resulted in a realistic description—compared to experiment—of pinch dynamics and current density distribution up to the time of minimum plasma radius, which is important to evaluate the focus quality of the lens. Equations of the inverse skin effect and the momentum conservation equation of magnetohydrodynamics were used. Due to the consideration of a finite plasma conductivity a finite current density distribution was computed, reaching 16 kA/cm2 at its maximum, which corresponds to a total current of about 280 kA at pinch time. The plasma is compressed from an initial radius of 100 mm to a pinch radius of about 14 mm within 3.33 μs. Thus, an ion density of 1.6×1018 cm−3 and a temperature of 30 eV is calculated. Although no shock wave is implemented in the model explicitly, a sharp radial density increase appears in the contraction phase and moves toward the axis with a velocity of up to 8×104 m/s. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871797
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  • 4
    Electronic Resource
    Electronic Resource
    Plasma lens fine focusing of heavy-ion beams (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2475-2477 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fine-focusing capability of a current-carrying, "active" plasma lens has been demonstracted for the first time. A cylindrically symmetric argon discharge plasma pulsed with an oscillating current of over 20 kA in amplitude served as a current conducting medium. With this plasma lens has been demonstrated for the first time. A cylindrically symmetric argon discharge plasma pulsed with an oscillating current of over 20 kA in amplitude served as a current conducting medium. With this plasma lens the diameter of an incident 2.2-GeV gold ion beam from the linear accelerator UNILAC at GSI-Darmstadt was focused from initially 10 to about 0.25 mm, at a focal length of only 140 mm. The gradient of the azimuthal magnetic field exceeded 120 T/m. The striking features of this first-order and strong-focusing plasma lens favor its use as a precise high-gradient focusing device for high-energy charged particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107443
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  • 5
    Electronic Resource
    Electronic Resource
    Homogeneous cylindrical plasma source for short-wavelength laser experiments (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2619-2621 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A plasma source suitable for repetitive operation, going beyond single shot experiments for research into soft x-ray lasers, is reported. Successful operation of an ultrafast, small-diameter, highly uniform z pinch has been achieved at currents of 35–50 kA, for a variety of gases and a large range of mass densities. Due to an efficient preionization of the working gas, a high-temperature and a high cooling rate of the plasma column are obtained. The plasma is less than 1 mm in radius, over 30 mm long, and over 1018 cm−3 ion density. A soft x-ray recombination laser experiment for the λ≈182 A(ring) Balmer-alpha-like transition in C vi is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104812
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  • 6
    Electronic Resource
    Electronic Resource
    Schlieren diagnostics of pulsed electron beam ablation of polymethyl-methacrylate (1992)
    Springer
    Applied physics 54 (1992), S. 520-522 
    Details
    ISSN: 1432-0630
    Keywords: 52.50 ; 52.80 ; 81.15Jj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The investigation of the interaction of pulsed electron beams with PMMA (polymethylmethacrylate) targets is reported. The electron beam of some 10−8 s in duration is produced in a pulsed low-pressure gas discharge. The beam power density of up to 108 W/cm2 leads to a surface plasma formation similar to that of the pulsed laser ablation process. The propagation of the ablated material and the shock wave inside the PMMA target are observed by means of Schlieren diagnostics. An electron density gradient of over 3×1019 cm−4 has been observed in the expanding plasma up to 1.5 μs after the plasma formation. During the early stage of expansion, the expansion velocity of the plasma plume as determined by the steep electron density gradient is around 105 cm/s. The pressure behind the shock front inside the PMMA target as determined from the shock velocity exceeds 0.3 Gpa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324332
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