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  • 1
    Electronic Resource
    Electronic Resource
    Investigations of cathode phenomena in pseudospark discharges (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5661-5665 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The cathode phenomena during the conduction phase of a pseudospark discharge are investigated with different cathode materials: Cu, Mo, Ni, Ta, and W/Re. The discharge gas was hydrogen with a gas pressure of 40 Pa. At a pulse duration of 2.7 μs and a maximum current of 9 kA, i.e., at a transferred charge of 11 mC/discharge, mass erosion rates of the cathode materials showed no significant material dependence after 106 discharges. Fast framing photography (end-on, exposure time: 5 ns) of the light emission from the cathode surface revealed several small spots simultaneously, distributed over a cathode surface of 1 cm2. The distribution of metal and hydrogen spectral lines at the cathode surface and in the gap were compared. Metal lines are localized on the cathode surface, whereas the hydrogen Balmer β-line is diffuse over the electrodes surfaces and the gap. Polished electrodes showed, after a single pulse, about 107 craters with 0.5–5 μm in diameter. This is leading to a local current density of about 108 A/cm2 in a single crater.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357071
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Current quenching in the pseudospark (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 574-576 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of current quenching in the pseudospark is presented. Current quenching during the conductive phase limits peak conduction current in certain thyratron switches. The quenching phenomenon also occurs in the pseudospark. However, a remarkable feature is that current quenching is observed only below currents of ≈ 2–3 kA, near the onset of superemissive behavior, and thus in the pseudospark is not an upper limit to high current operation. A mechanism involving an instability caused by ion depletion at the plasma boundary is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104591
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  • 4
    Electronic Resource
    Electronic Resource
    The bistability of the surface-stabilized ferroelectric liquid-crystal effect in electrically reoriented chevron structures (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 1253-1261 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-frequency electric field treatment irreversibly changes the chevron structure of a surface-stabilized ferroelectric liquid-crystal sample: the angle between the smectic layers and the surface normal decreases. As a result different textures appear, and a pronounced effect on the switching behavior is observed. The switching angle and the necessary pulse amplitudes at constant pulse width in order to obtain switching between both stable states have increased. The required reorientation voltages decrease with rising spontaneous polarization. This reorientation process is strongly influenced by the rubbing treatment of the alignment layer. The anchoring properties of the alignment layer seem to be directly responsible for the appearance of defects, for the initial switching angle, for the electric field strength necessary to reorient the chevron structure, and for the pulse amplitudes required to switch between both stable states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345700
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  • 5
    Electronic Resource
    Electronic Resource
    Bright dunes on Mars (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 397 (1999), S. 592-594 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Seasonal changes observed on the surface of Mars can in part be attributed to the transport of geological materials by wind. Images obtained by orbiting spacecraft in the 1970s showed large wind-formed features such as dunes, and revealed regional time-varying albedos that could be attributed ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/17557
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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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  • 7
    Electronic Resource
    Electronic Resource
    Diurnal cycles of formic and acetic acids in the northern part of the Guayana shield, Venezuela (1991)
    Springer
    Journal of atmospheric chemistry 13 (1991), S. 63-72 
    Details
    ISSN: 1573-0662
    Keywords: Tropical atmosphere ; formic acid ; acetic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Formic and acetic acids were measured in a scrub-grass savanna and in a nearby semideciduous forest. Gaseous HCOOH and CH3COOH were collected using the mist-scrubber technique, and were determined using ion chromatography. A strong diurnal cycle was observed at both sites, with higher mixing ratios during daytime. Concentrations in the savanna were always higher than in the forest. Most of the time HCOOH/CH3COOH ratios greater than one were recorded at the savanna site, and ratios less than one at the forest site. Boundary-layer mixing ratios in the savanna region, derived from measurements during midday, are 1.3±0.4 ppbv and 0.7±0.3 ppbv for HCOOH and CH3COOH. Dry depositions velocities between 0.5 and 1 cm s-1 were estimated for the savanna region. Atmospheric residence times of 〈3 days and 〉5 days were estimated for the rainy and dry season, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048100
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  • 8
    Electronic Resource
    Electronic Resource
    Behavior of atmospheric formic and acetic acid in the presence of hydrometeors (1992)
    Springer
    Journal of atmospheric chemistry 15 (1992), S. 101-115 
    Details
    ISSN: 1573-0662
    Keywords: Gas-liquid partitioning ; formic acid ; acetic acid ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The partitioning of formic and acetic acid between the atmospheric liquid and gaseous phase is modelled for a range of liquid water contents. At low liquid water content, formic acid is dissolved preferentially over acetic acid. Applying these results to the analysis of processes taking place in clouds, one can explain the frequently found enrichment of formic over acetic acid in rainwater, which results from selective transport by washout. We assess the ability of dew to act as a temporary sink and source for organic acids, and propose that the diel variation of mixing ratios often found during surface measurements, may in part be due to the dissolution in dew and subsequent evaporation on the following day.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00053753
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  • 9
    Electronic Resource
    Electronic Resource
    Coherent dark states of rubidium 87 in a buffer gas using pulsed laser light (1998)
    Springer
    The European physical journal 3 (1998), S. 159-161 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light - 42.62.Fi Laser spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The coherent dark resonance between the hyperfine levels F=1, m F =0 and F=2, m F =0 of the rubidium ground state has been observed experimentally with the light of a pulsed mode-locked diode laser operating at the D1 transition frequency. The resonance occurs whenever the pulse repetition frequency matches an integer fraction of the rubidium 87 ground state hyperfine splitting of 6.8 GHz. Spectra have been taken by varying the pulse repetition frequency. Using cells with argon as a buffer gas a linewidth as narrow as 149 Hz was obtained. The rubidium ground state decoherence cross section for collisions with xenon atoms has been measured for the first time with this method using a pure isotope rubidium vapor cell and xenon as a buffer gas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100500050162
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  • 10
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    XUV Amplification in a Recombiningz-Pinch Plasma (1996)
    American Physical Society
    Details
    Publication Date: 1996-04-22
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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