| 11. |
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| 12. |
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| 13. |
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| 14. |
- Saito, Y, et al.
(författare)
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Possibility of hard-target lidar detection of a biogenic volatile organic compound, alpha-pinene gas, over forest areas
- 2001
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Ingår i: Applied Optics. - 2155-3165. ; 40:21, s. 3572-3574
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Tidskriftsartikel (refereegranskat)abstract
- The absorption spectrum of alpha -pinene gas, a biogenic volatile organic compound, was directly measured with a pulsed mid-infrared laser. The maximum absorption wavelength was found to be similar to3.42 mum, and an absorption cross section of 4.8 x 10(-23) m(2) molec(-1) was obtained. A simple theoretical calculation with the measured spectral data showed that several hundreds of parts in 10(12) (ppt) of a-pinene gas in forest-mountain areas over a range of similar to 10 km were detectable by a long-path-averaged hard-target absorption lidar. Requirements for system development were also discussed. (C) 2001 Optical Society of America.
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| 15. |
- Sandsten, J, et al.
(författare)
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Real-time gas-correlation imaging employing thermal background radiation
- 2000
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Ingår i: Optics Express. - 1094-4087. ; 6:4, s. 92-103
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Tidskriftsartikel (refereegranskat)abstract
- Real-time imaging of gas leaks was demonstrated using an IR camera employing outdoor thermal background radiation. Ammonia, ethylene and methane detection was demonstrated in the spectral region 7-13 mu m. Imaging was accomplished using an optical filter and a gas-correlation cell matching the absorption band of the gas. When two gases, such as ammonia and ethylene, are absorbing in the same wavelength region it is possible to isolate one for display by using gas-correlation multispectral imaging. Results from a field test on a leaking gas tanker are presented as QuickTime movies. A detection limit of 200 ppm x meter for ammonia was accomplished in this setup when the temperature difference between the background and the gas was 18 K and the frame rate was 15 Hz. (C) 2000 Optical Society of America.
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| 16. |
- Sjöholm, Mikael, et al.
(författare)
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Atomic mercury flux monitoring using an optical parametric oscillator based lidar system
- 2004
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Ingår i: Optics Express. - 1094-4087. ; 12:4, s. 551-556
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Tidskriftsartikel (refereegranskat)abstract
- A newly developed optical parametric oscillator (OPO) based differential absorption lidar (DIAL) system has been applied to the monitoring of atomic mercury emissions at several chlor-alkali plants in Europe. The versatility of the system is illustrated by measured time series of mercury flux and movies of vertical and horizontal concentration distributions, which yield important input parameters for the environmental community. Long term measurements of the resonance absorption of mercury at 253.65 nm poses special demands, i.e. long term stability, on the light source that often have been hard to fulfill, in different respects, for standard OPO and dye laser based systems. Here, approaches to meet these demands are presented.
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| 17. |
- Sjöholm, Mikael, et al.
(författare)
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Optical parametric oscillator based lidar system applied to atomic mercury monitoring
- 2003
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Ingår i: 2003 Conference on Lasers and Electro-Optics Europe (CLEO/Europe 2003) (IEEE Cat. No.03TH8666). - 0780377346 ; , s. 471-471
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Konferensbidrag (refereegranskat)abstract
- Field measurements of mercury emissions has been performed by using a mobile lidar system. In this system an Nd:YAG-pumped OPO (Optical Parametric Oscillator) laser system is employed to generate a narrow band (better than 0.2 cm-1) UV beam at the mercury resonance absorption line at 253.65 nm. An inter-comparison of the lidar system and two different point monitoring systems has been performed showing excellent agreement between the instruments
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| 18. |
- Wangberg, I, et al.
(författare)
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Atmospheric mercury near a chlor-alkali plant in Sweden
- 2003
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Ingår i: Science of the Total Environment. - 1879-1026. ; 304:1-3, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric mercury species/fractions were measured near a chlor-alkali plant in Sweden during August 28 to September 4, 2001. The concentration of total gaseous mercury in the plume from the plant was measured using TEKRAN and GARDIS instruments. Gaseous elemental mercury was measured using a light detection and ranging (LIDAR) technique. From vertical LIDAR sweeps through the plume from the chlor-alkali plant mercury emission rates could be calculated. The concentrations of reactive gaseous mercury (RGM) in the plume and also inside the cell house were measured using annular KCl coated denuders. The RGM emission constitutes 0.5-1.0% of the total mercury emitted from the plant. The mercury concentration adsorbed on particles was measured as well as the mercury flux from soil. The data presented also include an intercomparison showing an excellent agreement between TEKRAN/GARDIS and LIDAR gaseous mercury measurements. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 19. |
- Weibring, Petter, et al.
(författare)
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Development and testing of a frequency-agile optical parametric oscillator system for differential absorption lidar
- 2003
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 74:10, s. 4478-4484
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Tidskriftsartikel (refereegranskat)abstract
- An all-solid-state fast-tuning lidar transmitter for range- and temporally resolved atmospheric gas concentration measurements has been developed and thoroughly tested. The instrument is based on a commercial optical parametric oscillator (OPO) laser system, which has been redesigned with piezoelectric transducers mounted on the wavelength-tuning mirror and on the crystal angle tuning element in the OPO. Piezoelectric transducers similarly control a frequency-mixing stage and doubling stage, which have been incorporated to extend system capabilities to the mid-IR and UV regions. The construction allows the system to be tuned to any wavelength, in any order, in the range of the piezoelectric transducers on a shot-to-shot basis. This extends the measurement capabilities far beyond the two-wavelength differential absorption lidar method and enables simultaneous measurements of several gases. The system performance in terms of wavelength, linewidth, and power stability is monitored in real time by an etalon-based wave meter and gas cells. The tests showed that the system was able to produce radiation in the 220-4300-nm-wavelength region, with an average linewidth better than 0.2 cm(-1) and a shot-to-shot tunability up to 160 cm(-1) within 20 ms. The utility of real-time linewidth and wavelength measurements is demonstrated by the ability to identify occasional poor quality laser shots and disregard these measurements. Also, absorption cell measurements of methane and mercury demonstrate the performance in obtaining stable wavelength and linewidth during rapid scans in the mid-IR and UV regions.
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| 20. |
- Weibring, Petter
(författare)
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Environmental Monitoring by Multi-Spectral Lidar Techniques
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Multi-spectral lidar (light detection and ranging) techniques have been developed and employed in various environmental studies, ranging from concentration mapping of volcanic emissions to fluorescence imaging of historical monuments. In both absorption measurements of gaseous species and fluorescence imaging of stones, multiple wavelength excitation and multiple wavelength detection have been applied. A mobile frequency agile lidar system, using all-solid-state technology, has been constructed for range resolved atmospheric gas concentration measurements in the ultraviolet, visible and mid-infrared wavelength regions. A measurement method based on multivariate statistical techniques has been developed to analyse the composition of complex gas mixtures from their combined absorption spectrum. Industrial emissions of mercury from chlor-alkali plants and hydrocarbons from a test site, have been studied to explore the capabilities of the new lidar system. Local polynomial regression with local data driven bandwidths has been developed and utilised as a flexible technique for evaluating DIfferential Absorption Lidar (DIAL) data. The method allows an optimally adapted range resolution and control of measurement accuracy. A new method for gas flux measurements using a combination of DIAL and wind videography has been developed. Validation of the method has been performed during measurements of sulphur dioxide at a paper and pulp mill. The emission of sulphur dioxide from the Italian volcanoes Mt Etna, Stromboli and Vulcano has been studied in several ship-borne measurements combining simultaneous passive and active optical spectroscopy techniques. The deviations between the instruments could be explained by modelling the light scattering through the plume, which allowed correction of data for most situations. Fluorescence imaging of the facades of the Lund Cathedral (Sweden) and the Parma Cathedral and Baptistery (Italy), employing a scanning fluorescence lidar system and multivariate analysis techniques, has been performed allowing classification of different stone types and algal colonisation. Range resolved fluorescence measurements of ocean, coastal and harbour water have been performed during a ship-borne cruise in the Mediterranean sea.
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