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  • 1
    ISSN: 1432-0649
    Keywords: 42.80 ; 07.65 ; 82.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper reports and discusses, for the first time, the all-optical remote monitoring method for spilled dispersals or leakages in air of city gas through the nearinfrared absorption of CH4 gaseous molecules as one of its major constituents, using a very low-loss optical fiber network and compact absorption cells in conjunction with high radiant InGaAsP light-emitting diodes (LEDs). For this new application, the near-infrared absorption spectra of city gas (Sendai, Japan) were measured and analyzed to find a relatively strong absorption due to thev 2 + 2v 3 combination band of CH4 molecules around the wavelength region of 1.33 μm. By using a 2-km long very low-loss silica optical fiber link, this fully optical system was demonstrated to be feasible, safe and capble of achieving reproducibly the detection sensitivity of nearly 1 Torr of CH4 gas in air, i.e., 2.6% of the lower explosion limit of CH4 density in air. This result supports the conclusion that the alloptical remote sensing system incorporating very low-loss optical fiber networks and LEDs or laser diodes (LDs) in the near-infrared region can be extensively utilized for the real-time detection and surveillance of spills or leakages of the city gas or any other gas mixtures as well as various combustible, explosive, dangerous, and toxic gases not onlyin industrial and mining complexes but also in urban and residential areas.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 38 (1985), S. 11-15 
    ISSN: 1432-0649
    Keywords: 42.68 ; 42.80 ; 07.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper reports for the first time the fully optical remote monitoring of low-level CH4 gas with a wide area coverage of 10 km in diameter realized by utilizing ultralowloss silica optical fibre link and a compact absorption cell in conjunction with highly radiant InGaAsP and InGaAs light emitting diodes (LEDs) in the near infrared region. For this novel application, the near-infrared absorption spectra of CH4 molecules were measured and studied involving the ν2+2ν3 combination band around 1.33 μm and the 2ν3 overtone band around 1.66 μm. This fibre-optic system was demonstrated to be feasible and sufficiently sensitive and safe as being a practical CH4 gas remote sensor whose detection sensitivity is normally required to be 25% of the lower explosion limit (LEL) of CH4 gas in air. This result verifies a large potential for applying extensively to various strategic points within the environment, such as industrial and mining complexes as well as urban and residential areas, with considerably increased reability, safety and marketability over the presently available techniques.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of infrared and millimeter waves 5 (1984), S. 1039-1052 
    ISSN: 1572-9559
    Keywords: H2O laser ; Faraday rotation ; polarimetry ; far-infrared ; plasma diagnostics ; compact toroid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A fast response frequency-modulated interferometric polarimeter was designed and constructed with a single 28 μm H2O laser for high density plasma diagnostics. This newly developed modulation system employs an electro-magnetically driven movable mirror to achieve the modulation frequency beyound 1 MHz for about 100 μs duration. The movable mirror performance is studied experimentally in detail. The determination of the Faraday rotation angle is based on the zero-crossing method for the observed beat signals produced by two kinds of rotating plane-polarized waves. The feasibility of the polarimeter constructed was verified in experiments of a field-reversed thetapinch plasma.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of infrared and millimeter waves 2 (1981), S. 1199-1208 
    ISSN: 1572-9559
    Keywords: water vapor laser ; plasma diagnostics ; interferometer ; waveguide laser ; far-infrared
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A high-power CW 27.972 μm water vapor laser has been constructed in order to use as a light source of an interferometer for plasma diagnostics. The laser consists of 220 cm length and 2.0 cm small bore Pyrex glass discharge tube, semi-confocal resonator and Michelson coupler. From the measurement of cavity detuning curves, it is found that two waveguide modes, EH11 and EH21 oscillate. The increase of the output power is found to become more than seven times larger by adding He(50%)−H2(50%) mixed gas. Under the optimum condition, the maximum output power of 65 mW or the output power per unit cavity volume of 83 μW/cm3 is obtained.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of infrared and millimeter waves 4 (1983), S. 549-559 
    ISSN: 1572-9559
    Keywords: interferometer ; polarimeter ; water-vapor laser ; far-infrared ; plasma diagnostics ; compact toroid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A high-power CW 27.972 μm water-vapor laser has been developed for interferometric and polarimetric measurements of plasmas. The maximum output power and the power density in the cavity of the laser with 2.0 cm bore and 220 cm length reach 85 mW and 109 μW/cm3, respectively. An interferometer using this laser is constructed and its performance is examined as a study on polarimetric method of magnetic field measurement. Preliminary interferometric experiments are also carried out on a compact toroidal plasma with field-reversal configuration.
    Type of Medium: Electronic Resource
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