The Review of Laser Engineering
Online ISSN : 1349-6603
Print ISSN : 0387-0200
ISSN-L : 0387-0200
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Volume 24, Issue 5
Displaying 1-12 of 12 articles from this issue
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  • [title in Japanese]
    Chiyoe YAMANAKA
    1996 Volume 24 Issue 5 Pages 531-532
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.531
    JOURNAL FREE ACCESS
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  • Laser Triggered Lightning - Scenarios and Issues
    Tatsuhiko YAMANAKA
    1996 Volume 24 Issue 5 Pages 533-540
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.533
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    Control of lightning is a dramatic challenge to nature. The lightning attacks to the electric power line make a lot of economical loss in the sophisticated modern society since electric power failure induces a lot of trouble in the computerized systems even if it is very short time. If the lightning could be controlled one will be free from such a trouble and save the cost expensed for electric power failure guard system. The scenarios and issues of laser triggered lightning are reviewed presenting some experimental results as well as the mechanisms and types of lightning, characteristics of the long gap electric discharge and some results of triggered lightning by rockets.
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  • How to Forecast the Occurrence of Lightning Discharges
    Zen KAWASAKI, Masakazu WADA, Tomoo USHIO, Jun ONUKI
    1996 Volume 24 Issue 5 Pages 541-546
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.541
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    We believe that it is impossible to realize the laser triggered lightning without forecasting the occurrence and the inception of lightning discharges. As the sub-group of Laser Triggered Lightning Project, we are assigned to achieve the forecast of lightning. Several categories of forecast can be considered, and in this article we introduce the two different types of forecasts which are conducted by our group. The first one is a second order forecast to fire the laser to trigger lightning. The second one is an hour order forecast to stand by the whole equipments by knowing the thunderstorm occurrence and/or the approaching to the experiment site.
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  • The Field Experiments of Laser Triggered Lightning
    Shigeaki UCHIDA, Yoshinori SHIMADA, Hirohiko YASUDA, Kouji TSUBAKIMOTO ...
    1996 Volume 24 Issue 5 Pages 547-555
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.547
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    A field experimental site for laser triggered lightning (LTL) has been prepared targetting the winter thunderstorms in Hokuriku region. This paper discusses the results from laboratory experiments and field observation on winter thunderstorms at Mihama district. A new scheme of determining the laser irradiation timing, the PB (Preliminary Breakdown) trigger, and its preliminary results on LTL are also described.
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  • Formation Processes of Laser Induced Discharge Path
    Michihiro UCHIUMI, Takahiro IMAIZUMI, Toshikatsu TANAKA, Katsunori MUR ...
    1996 Volume 24 Issue 5 Pages 556-563
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.556
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    It is well known that plasma beads are produced in the atmosphere by a focused high-power laser beam. The characteristics of propagation of a CO2 laser beam in the atmosphere including the plasma beads produced by focusing the laser beam were investigated. The optical air-breakdown mechanism was treated by empirical relations instead of taking inverse bremsstrahlung into considerations. A simple equation was newly proposed here to describe processes of growing of plasma beads. The simulated results on the density of plasma beads were qualitatively in agreement with experimental results. The model consisting of these procedures has a possibility to predict the density of plasma beads which are produced in the atmosphere by a CO2 laser owing to ignition of atmospheric aerosols.
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  • Artificial Triggered Lightning Using Ultraviolet Lasers
    Guiding of the Electrical Discharges by an Excimer Laser
    Megumu MIKI, Atsushi WADA, Takatoshi SHINDO
    1996 Volume 24 Issue 5 Pages 564-571
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.564
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    Guiding and triggering of the electrical discharges in lm air gaps by excimer lasers (KrF (λ=248nm), ArF (λ=193nm)) have been performed. A laser pulse (KrF: 750mJ, ArF: 550mJ) produced a plasma channel over a distance of more than 0.5m by focused with a lens. Characteristics of guided discharges along the plasma channel were investigated in detail. From these results, it is found that an excimer laser pulse can guide the positive discharges and propagate in the plasma channel produced by itself without loss. However the excimer lasers have little ability to trigger the discharges. Further the guiding ability is not maintained for a long time compared with that of infrared lasers. On the basis of these experimental results, we discussed the basic concept of the laser triggered lightning with an excimer laser.
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  • Study on Laser Triggered Discharge Using a CO2 Laser
    Yoshinori SHIMADA, Shigeaki UCHIDA, Hirohiko YASUDA, Shinji MOTOKOSHI, ...
    1996 Volume 24 Issue 5 Pages 572-581
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.572
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    We are preparing a laser triggered lightning method for the winter thunderstorm. Using a - 150-J electron beam excited CO2 laser, we obtained a laser plasma channel consisting of many plasma beads made of ionized aerosols in the atmosphere. The laser plasma channel initiates an electrical streamer and propagates a leader. We discuss experimental results on the critical conditions for initiating streamer from a laser plasma channel and for leader propagation through a laser plasma channel.
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  • Fundamental Experiments on Laser Triggered Lightning
    Plasma Generation under Winter Thunderstorms
    Hirohiko YASUDA, Shigeaki UCHIDA, Yoshinori SHIMADA, Shinji MOTOKOSHI, ...
    1996 Volume 24 Issue 5 Pages 582-589
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.582
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    It is a crucial issue to make an intense plasma channel in the atmosphere for laser triggered lightning. The laser characteristics of laser propagation and plasma generation have been studied under various weather conditions. The line density of plasma channel in snowy weather is less than that in fine weather due to the laser energy attenuation and the decrease of aerosols, the cores of plasma beads, by snow. To initiate a leader at the top of lightning tower, the line density of plasma channel is needed to be over one hundred per meter. Some remedies to overcome this effects will be discussed.
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  • Study of Laser Triggered Lightning by Simulation
    Simulation on Start-up of Discharges from Discontinuous Plasmas
    Hiroyuki FURUKAWA, Shigeaki UCHIDA, Yoshinori SHIMADA, Hirohiko YASUDA ...
    1996 Volume 24 Issue 5 Pages 590-595
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.590
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    We have developed a simulation code on the discharges from discontinuous plasmas to study laser triggered lightning theoretically. And the simulations of the discharges with 2m gap from discontinuous plasmas, of which intervals are 5mm or 10mm, are performed. The model is based on plasma approximation. The effects of distortion of external electric field by tower and the progresses of the leader are included. The speed of the progresses of the leader obtained by simulations is about 3×106m/s which agrees with experimental results.
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  • Development of a Plasma Shutter for Fast Truncation of CO2 Laser Beams
    Koichi SASAKI
    1996 Volume 24 Issue 5 Pages 596-601
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.596
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    A plasma shutter having two ZnSe lenses has been developed with the intention of applying it to the generation of ultrashort pulses in the far-infrared and millimeter wavelength range. A fast truncation time of about 1.5 ns was obtained by the plasma shutter, which is approximately the same as the response time of the measurement system. It was found experimentally that truncation waveforms were dependent on both the detection location in the laser beam cross section and the N2 gas pressure inside the shutter chamber. A physical explanation for the above experimental results is given briefly.
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  • Flash-Lamp-Pumped Cr:LiSAF Amplifier
    Hideyuki TAKADA, Kenzo MIYAZAKI, Kenji TORIZUKA
    1996 Volume 24 Issue 5 Pages 602-608
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.602
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    We have developed a flash-lamp-pumped Cr:LiSAF laser amplifier that is capable of producing ultrashort pulses with a peak power of - TW. Experiments of its normal oscillation, small-signal gain measurement, and chirped-pulse amplification have been performed under the same pumping condition. The Cr:LiSAF laser design and its characteristic properties obtained are reported.
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  • Time-Resolved Fluorescence Spectrophotometer Using a Traveling Wave Plate Type Streak Camera
    Seiji AKIMOTO, Akira TAKAHASHI, Katsuyuki KINOSHITA, Motoyuki WATANABE ...
    1996 Volume 24 Issue 5 Pages 609-614
    Published: May 31, 1996
    Released on J-STAGE: February 26, 2010
    DOIhttps://doi.org/10.2184/lsj.24.609
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    We present a new type of streak camera which contains a traveling wave plate as deflection plate to obtain high time resolution. Combined with a Ti:sapphire laser system and a polychromator, we obtain an instrumental response function (IRF) of 8 ps FWHM. Application of this streak camera for ps measurements is exemplified by measuring the fluorescence lifetimes of a standard molecule and the time-resolved fluorescence spectra of 9, 9'-bianthryl in ethanol.
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