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- Acharya, B. S., et al.
(author)
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Introducing the CTA concept
- 2013
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In: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 43, s. 3-18
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Journal article (other academic/artistic)abstract
- The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. (C) 2013 Elsevier B.V. All rights reserved.
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| 6. |
- Brackmann, C., et al.
(author)
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Strategies for formaldehyde detection in flames and engines using a single-mode Nd : YAG/OPO laser system
- 2004
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In: ; , s. 293-293
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Conference paper (peer-reviewed)abstract
- Technical developments for the detection of formaldehyde using laser-induced fluorescence were presented. A technique for simultaneous detection of formaldehyde and OH using one laser system was presented. The combined formaldehyde and OH technique was applied in laboratory flames and a small spark-ignition engine. The iodine measurement was performed in a cell using the second harmonic of the single-mode Nd:YAG laser and used for wavelength calibration of the laser. Spectral studies of the fluorescence emission indicated that both the peaks as well as the continuous part originated from formaldehyde. This is an abstract of a paper presented at the 30th International Symposium on Combustion (Chicago, IL 7/25-30/2004).
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| 7. |
- Li, Z. S., et al.
(author)
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Mid-infrared PS and LIF detection of CH4 and C2H6 in cold flows and flames at atmospheric pressure
- 2004
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In: ; , s. 10-11
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Conference paper (peer-reviewed)abstract
- Mid-IR polarization spectroscopy (IRPS) and laser-induced fluorescence were applied for detection of CH4 and ethane in 1 atm cold flows and flames. The dependence of IRPS and IRLIF signal of CH4 on different buffer gases, including He, Ar, N2, and CO2 were studied. Simultaneous measurements of IRPS and IRLIF signals allowed a direct comparison of the two techniques. IRPS was superior in detection sensitivity and background discrimination. IRPS excitation scans of a CH4 and ethane mixture diluted in argon were also carried out in a jet at ambient pressure and temperature. Lines in the spectrum belonging to CH4 and ethane were fully recognized and assigned. From the ethane lines in the IRPS excitation spectrum, a detection limit of 50 ppm was conservatively estimated, indicating that IRPS is a promising sensitive technique for hydrocarbon identification and detection. CH4 IRPS detection in a CH4/H2/air premixed flat flame was demonstrated, with spatially resolved IRPS CH4 measurements along different heights in the flame. This is an abstract of a paper presented at the 30th International Symposium on Combustion (Chicago, IL 7/25-30/2004).
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| 9. |
- Brackmann, Christian, et al.
(author)
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Strategies for formaldehyde engines using a single-mode detection in flames and Nd : YAG/OPO laser system
- 2005
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In: Applied Spectroscopy. - 1943-3530. ; 59:6, s. 763-768
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Journal article (peer-reviewed)abstract
- This paper presents technical developments for the detection of formaldehyde (CH2O) using laser-induced fluorescence. The easily accessible third harmonic of the Nd:YAG laser at 355 nm was used for excitation of formaldehyde. In order to investigate potential background fluorescence, e.g., from large molecules such as polyaromatic hydrocarbons, special attention was paid to investigating the possibility of scanning the wavelength of a single-mode Nd:YAG laser under the gain profile, similar to 3 cm(-1), on and off resonance. Furthermore, a technique for simultaneous detection of formaldehyde and 011 using one laser system is presented. The single-mode Nd:YAG laser at 355 nm in combination with an optical parametric oscillator (OPO) laser tuned to 283 nm was used for simultaneous two-dimensional imaging of both species using one charge-coupled device (CCD) detector equipped with a dual filter image separator. The techniques are demonstrated with measurements in laboratory flames and the combined measurements are also demonstrated in an engine.
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| 10. |
- Li, Zhongshan, et al.
(author)
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Detection of methane with mid-infrared polarization spectroscopy
- 2004
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In: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 79:2, s. 135-138
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Journal article (peer-reviewed)abstract
- We report on the application of polarization spectroscopy in the midinfrared spectral region for the detection of methane by probing its asymmetric ro-vibrational transitions. Tunable infrared laser radiation, near 3.4 mum, was obtained from difference-frequency generation in a LiNbO3 crystal. Infrared polarization spectroscopy (IRPS) spectra of the P, Q and R branches of the nu(3) band, recorded with both linearly and circularly polarized pump beams, are presented. The experiments were performed in an atmospheric pressure gas jet with methane diluted with Ar. An IRPS spectrum with signal-to-noise ratio better than 10(4) was observed. The dependence of the IRPS signal intensity on the methane mole fraction and on the pumping laser power density was investigated.
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| 11. |
- Li, Zhongshan, et al.
(author)
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Mid-infrared polarization spectroscopy of polyatomic molecules: Detection of nascent CO2 and H2O in atmospheric pressure flames
- 2005
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In: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 407:4-6, s. 243-248
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Journal article (peer-reviewed)abstract
- We report the application of mid-infrared polarization spectroscopy (IRPS) for detection of nascent CO2 and H2O in atmospheric pressure flames. The recorded IRPS spectra demonstrated both the quantitative nature of the method and the suppression of strong infrared emission from flames. In spite of the high line-density of the hot polyatomic ro-vibrational spectrum, lines belonging to different CO2 and H2O hot bands were recognized in the chosen spectral region, which ensures the species-selective application of IRPS.
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| 12. |
- Li, Zhongshan, et al.
(author)
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Mid-infrared PS and LIF detection of CH4 and C2H 6 in cold flows and flames at atmospheric pressure
- 2005
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In: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 30:1, s. 1629-1636
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Journal article (peer-reviewed)abstract
- Mid-infrared polarization spectroscopy (IRPS) and laser-induced fluorescence (IRLIF) have been applied for detection of methane and ethane in atmospheric pressure cold flows and flames. Lines belonging to the asymmetric C-H stretching vibration bands v3 and v7 for methane and ethane, respectively, were probed with a tunable infrared laser beam at about 3.4 μm, which was obtained from difference frequency generation in a LiNbO3 crystal pumped by a dye-laser beam and a Nd:YAG fundamental laser beam. The dependence of IRPS and IRLIF signal of CH4 on different buffer gases, including He, Ar, N2, and CO2 was investigated. Simultaneous measurements of IRPS and IRLIF signals allowed a direct comparison of the two techniques, and IRPS was found to be superior in detection sensitivity and background discrimination. IRPS excitation scans of a methane and ethane mixture diluted in Ar were also performed in a jet at ambient pressure and temperature. Lines in the spectrum belonging to methane and ethane were fully recognized and assigned. From the ethane lines in the IRPS excitation spectrum, a detection limit of 50 ppm was conservatively estimated, and this indicates that IRPS is a promising sensitive technique for hydrocarbon identification and detection. Finally, CH4 IRPS detection in a CH4/H2/air premixed flat flame was demonstrated, with spatially resolved IRPS CH4 measurements along different heights in the flame.
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| 13. |
- Walewski, Joachim, et al.
(author)
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Soot visualisation by use of laser-induced soot vapourisation in combination with polarisation spectroscopy
- 2003
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In: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 77:4, s. 447-454
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Journal article (peer-reviewed)abstract
- A novel approach to the visualisation of soot is presented. It relies on a combination of laser-induced soot vapourisation and consecutive polarisation spectroscopy. Upon soot vapourisation, molecular fragments (for example, C-2) emerge, and may serve as effective tracers for soot. In this study we demonstrate that saturated polarisation spectroscopy on photoinduced C-2 can be exploited for soot detection. Signal maps featuring high signal-to-noise ratios were readily recorded in ethyne-rich flames and any spurious background, for example, caused by Rayleigh scattering, was successfully suppressed by means of spatial filtering. Additionally, investigations were carried out addressing how the attained signals correlate with local soot volumne fractions. For this purpose, height profiles of C-2 number densities inferred from the polarisation spectroscopy signal maps were compared with profiles of the soot volumne fraction inferred from measurements with laser-induced incandescence. For low soot volumne fractions, the shapes of the height profiles from our approach agree rather well with the latter; they do not agree for higher soot volumne fractions. Further investigation is required to resolve this discrepancy. Scattering from particles in the Mie scattering range may hamper the application of this approach, and avenues are suggested for extending the applicability of the approach presented to large soot particles.
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