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  • 1
    Electronic Resource
    Electronic Resource
    Scaling and performance of CO2 lasers at supra-atmospheric pressure (1985)
    Springer
    Applied physics 37 (1985), S. 171-179 
    Details
    ISSN: 1432-0649
    Keywords: 42.55D ; 42.60B ; 58.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The performance of a compact uv photo-preionized TE laser is studied in the pressure range 1–5 bar. As the pressure is increased, the laser pulse shape is little altered, but both the peak power and the total output pulse energy increase significantly with pressure, even for constant input electrical energy. For various gas mixtures and excitation source capacitors the measurements suggest approximate output energy scaling with the product of the source charge per unit electrode area [C.m−2] and the molecular partial pressure [CO2+N2+CO]. This is explained in terms of the pressure-dependent discharge impedance. An input-energy-related discharge instability limits the optimum laser pressure to 1.5–2.5 bar, and we show that, at constant input energy, the instability boundary depends on the molecular partial pressure alone. The pre-ionization photo-electron yield varies negligibly with pressure, but the discharge tolerance to added oxygen decreases asp −3 top −4, dependent on gas mixture. Nevertheless sealed operation for 〉105 shots has been obtained with a 5% CO2∶5% CO∶3% N2∶2% H2∶85% He gas mixture at a total pressure of 5 bar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692081
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  • 2
    Electronic Resource
    Electronic Resource
    X-ray preionized CO2 laser (1985)
    Springer
    Applied physics 37 (1985), S. 219-221 
    Details
    ISSN: 1432-0649
    Keywords: 42.55D ; 33.80E ; 52.80 ; 42.60B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A short pulse (100 ns) high-energy x-ray source has been used to preionize a transversely excited carbon dioxide gas discharge laser of 600 cm3 active volume. The maximum output power of 60 MW in a 50 ns FWHM pulse was achieved from a CO2−N2−He−CO−Xe static gas mixture at 600 Torr pressure. The energy conversion efficiency was 6%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692945
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Ultraviolet photoionization in CO2 TEA lasers (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 528-536 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The factors affecting spark ultraviolet (UV) emission and transmission, photoionization, and photoelectron loss mechanisms in CO2 TEA laser gas mixtures have been investigated and compared with the results of other workers. We found two different sources of UV radiation: N2 and an unidentified emitter, postulated to be associated with ionized electrode material; C (from CO and CO2) appeared to have little effect. UV emission was directly proportional to the amount of stored electrical energy in the spark-discharge circuit and to the cube of the peak current produced by the discharge of this energy. The uniformity of preionization produced by two kinds of spark-free space and notched surface guided was examined and the free-space spark was found to be superior. Photoionization was found to be due to the presence of low ionization potential (IP) alkenes in unseeded and fresh gas mixtures and also to NO and NO2 in sealed devices—these were formed as a result of spark plasma reactions. The nature of the photoionization process in NO and C3H6 (an alkene) was investigated; both were ionized in a single-step process. The absorption coefficient for ionizing radiation in CO2 was measured in a gas mixture containing 9% N2 and a N2 free mixture and values of 1.3 and 1.9 cm−1 atm−1 were obtained. It is thought that this may be due to changes in the spark UV emission spectrum when N2 is present. The loss of photoelectrons by third body attachment to NO, NO2, and O2 was monitored and only the attachment to O2 was found to be significant. However, the oxides of N can play a dominant role in the subsequent negative ion reactions on a millisecond timescale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341992
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  • 4
    Electronic Resource
    Electronic Resource
    Negative ion effects in CO2 convection laser discharges (1978)
    Springer
    Applied physics 16 (1978), S. 111-118 
    Details
    ISSN: 1432-0630
    Keywords: 42.55D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Negative ions are computed to be formed on a time scale and in quantities such that they may be a cause of plasma instability observed in low pressure electrical discharge convection CO2 lasers. In a typical CO2−N2−He−H2O laser mixture the principal ions are CO 3 − , CO 4 − and H− with the total negative ion densityn − given by 0.1n e 〈n −〈n e , wheren e is the electron density: but if the gases are re-cycled or if there is an air leak NO 2 − and NO 3 − are formed in significant amounts andn − can become greater thann e in a time considerably less than the gas dwell time in the electrical excitation discharge. CO is effective in reducingn − in a system without re-cycling, but is ineffective in a re-cycled system with the oxides of nitrogen present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00931431
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  • 5
    Electronic Resource
    Electronic Resource
    Effective and simplified hybrid TEA laser design and operation (1984)
    Springer
    Applied physics 33 (1984), S. 99-101 
    Details
    ISSN: 1432-0649
    Keywords: 42.60B ; 42.55D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A compact hybrid TEA CO2 laser has been developed which, when operated with the low pressure section well below oscillation threshold, demonstrates that little cw gain is necessary to ensure single longitudinal mode (SLM) output pulses with peak power, energy and pulse shape approaching those of normal multi-mode operation. This has allowed reliable SLM operation to be obtained with a very short, wide bore rf-excited low-pressure section, making feasible simple single-mode, large-aperture TEA lasers with high peak powers and energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00688354
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  • 6
    Electronic Resource
    Electronic Resource
    Identification of the origins of photoionisation in CO2 TEA lasers (1984)
    Springer
    Applied physics 33 (1984), S. 1-5 
    Details
    ISSN: 1432-0649
    Keywords: 42.55 Dk ; 33.80 eH ; 52.80-s
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In sealed CO2 spark preionised lasers the preionisation is largely due to photoionisation of NO and NO2, in seeded TEA lasers it originates from the low ionisation potential additive used. Unseeded and flowing gas lasers can still be successfully preionised but the source of this preionisation has remained a mystery; previous attempts to isolate and identify low I.P. gaseous impurities have failed. We have now identified these, using a combination of cryogenic impurity concentration and mass spectroscopy and found them to be a complex mixture of hydrocarbons (C2−C7). Of these hydrocarbons, the alkenes are found to be predominantly responsible for the photoionisation and are present in concentrations of ∼ 0.5 ppm. Deliberate addition of one of these alkenes, propene, to a uv preionised CO2 TEA laser was found to enhance the lasers performance at high energy loadings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690018
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