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  • 52  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 48 (1989), S. 1-20 
    ISSN: 1432-0649
    Keywords: 42.55E ; 42.60B ; 52
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied RF discharges as excitation mechanisms for distributed feedback (DFB) CO2 lasers. For CO2 laser plasmas the reduced electric fieldE/N has to be in a well-defined range. The reduced electric fieldsE/N of gas discharges in the narrow gaps with widths of the order of 100 μm required for DFB are considerably above this range. In order to study the feasibility of these RF-excited discharges for DFB CO2 lasers we have measured the electron temperatureT e in their plasmas. From helium-line-intensity ratios we have deduced a lower limit of the electron temperatureT e of 4eV. The observed high intensities of bands of singly ionized nitrogen indicate an even higher electron temperature, but an efficient pumping of the upper laser level is not possible with an electron temperature above 2.5 eV. We have estimated the electron densityn e and the current densityj e from ratios of the intesities of forbidden and allowed helium lines. The high current densityj e is in the range of abnormal glow discharges. In the gas discharges between narrow gaps the electron oscillation amplitudex e is large than the electrode separationd. In order to replace the resulting high electron losses a high electron temperatureT e is necessary to sustain the gas discharge. Because of this high electron temperatureT e an efficient pumping of the upper laser level is not possible.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 38 (1985), S. 41-49 
    ISSN: 1432-0649
    Keywords: 34 ; 52
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This study is devoted to the design, the operational characteristics and optimization of a self-field magnetoplasmadynamic (MPD) arc in view of its applications as a thruster and as a plasma source for recombination lasers. Its principal characteristics, i.e. its terminal voltageV E1and the exhaust speedu eas functions of the square of the discharge currentI divided by the mass flow ratem are determined experimentally for atomic propellants. On the basis of measured diagramsV E1versus (I 2/m) our discharge configuration is found to be well comparable to those applied by other laboratories. However, in order to further increase the specific impulse, these devices should make use of propellants of low molecular weight. Therefore, we also show that these thrusters can be operated in a quasi-steady mode for atomic as well as for molecular propellants, e.g. H2, N2, O2. Existing theories and interpretations of observations on atomic propellants are reviewed and, if possible, extended to explain the experimental results obtained with molecular propellants. In the framework of these extended theories the high-power limit of a stable operation is well understood.
    Type of Medium: Electronic Resource
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