The Review of Laser Engineering
Online ISSN : 1349-6603
Print ISSN : 0387-0200
ISSN-L : 0387-0200
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Volume 16, Issue 5
Displaying 1-5 of 5 articles from this issue
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  • [title in Japanese]
    Takashi TOKUYAMA
    1988 Volume 16 Issue 5 Pages 240
    Published: May 28, 1988
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.16.240
    JOURNAL FREE ACCESS
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  • New Aspect s of UV Photochemistry
    Formation and Reactions of Hot Molecule
    Nobuaki NAKASHIMA
    1988 Volume 16 Issue 5 Pages 241-251
    Published: May 28, 1988
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.16.241
    JOURNAL FREE ACCESS
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    UV photochemistries of benzene, alkylbenzenes, and olefins are described from a new point off view: hot molecule mechanism. Hot molecule (denoted as S0**) is a highly excited vibrational state in the ground electronic state. The primary process of these molecules irradiated with Ar F laser light (193.2 nm) is internal conversion to the ground state in the gas phase and S0**forms. The equivalent vibrational temperatures of S0**are very high 2000-4000K. Subsequent reactions are found to be similar to those driven by thermal energy.
    Hot molecule (S0**) can be an intermediate of UV multiphoton dissociation. S0** shows strong absorption in the U V region and hence efficiently absorbs a second photon which causes dissociation. Radical fragmentations are major reactions for this new multiphoton chemistry.
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  • Numerical Calculation of Shapes Machined with Pulsed YAG Laser (3rd Report)
    Observations of Reflected Laser Light, Passed Laser Light and Laser Light Transmitted through the Plume during Laser Machining
    Takehiro WATANABE, Yoshitaro YOSHIDA, Chikara SHIMO
    1988 Volume 16 Issue 5 Pages 252-266
    Published: May 28, 1988
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.16.252
    JOURNAL FREE ACCESS
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    Construction of machining mechanism with laser beam is useful for deciding the algorithm in case of calculating the machined shapes. In the former paper, melting and removing processes were investigated through machinability of various metals with laser beam. In this paper, the mechanism was investigated through observations of various phenomena in laser machining. The results obtained are as follows. (1) The reflectivity of laser beam at the work surface decreased gradually with increasing the temperature of workpiece and rapidly with generation of a keyhole in the molten pool. (2) The diameter and the penetration speed of the keyhole were estimated by observations of laser light passing through the workpiece. (3) The speed decreased with an increase in the machined depth, and was influenced mainly by thermal diffusivity of the workpiece and melting point in case of low and high power density, respectively. (4) The plume produced with laser irradiation was observed by high speed photograph and the transmissivity of the plume was estimated by observations of laser light transmitting through the plume. (5) About 20% of laser beam energy was absorbed by the plume in pure aluminum and about 38% in stainless steel (SUS304) when the laser beam was irradiated with power density of12.0MW/cm2 and pulse duration of 4.5ms.
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  • Study of Triggering Lightning by using TEA CO2 Laser
    Taro UCHIYAMA, Michio HIROHASHI, Hidenori MIYATA, Tatsuhiko SAKAI
    1988 Volume 16 Issue 5 Pages 267-277
    Published: May 28, 1988
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.16.267
    JOURNAL FREE ACCESS
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    A possibility of triggering lightning using laser is investigated. A long plasma channel is produced in atmospheric air when pulsed CO2 laser radiation is focused by a mirror. Length of plasma channels are measured for focal length of 10m, 20m, 30m, 45m and 60m respectively. A length of 30m plasma channel is produced when a energy. of 50 J unstable mode is focused by the mirror having 60m focal length. The propagated unstable mode patterns and intensities are calculated using the Fresnel diffraction integral, and compared with experimental results.
    The plasma channel produced by the mirror of 10m focal length is applied for triggering electrical discharge. The arc which has the length of 1.8m is triggered and guided by the plasma channel, and some characteristics are obtained.
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  • High Precision Displacement-Measurement Using a Phase Detection of Young's Fringes
    Suezou NAKADATE
    1988 Volume 16 Issue 5 Pages 278-286
    Published: May 28, 1988
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.16.278
    JOURNAL FREE ACCESS
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    A method for detecting a shift of Young's fringes is applied to a high precision measurement of a displacement of a piezoelectric transducer (PZT). An arctangent calculation with Fourier cosine and sine integrals of the fringe profile gives the phase of Young's fringes, which is proportional to the displacement of the PZT. The method of the phase detection is described with theoretical error estimations. Experimental results of the PZT displacement using a non-polarizating Michelson interferometer are presented with estimations of the measurement accuracy and the minimum detectable phase change.
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