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Stuttgart, Germany

Pandolfi M.,CSIC - Institute of Environmental Assessment And Water Research | Martucci G.,National University of Ireland | Querol X.,CSIC - Institute of Environmental Assessment And Water Research | Alastuey A.,CSIC - Institute of Environmental Assessment And Water Research | And 4 more authors.
Atmospheric Chemistry and Physics | Year: 2013

Continuous measurements of surface mixed layer (SML), decoupled residual/convective layer (DRCL) and aerosol backscatter coefficient were performed within the Barcelona (Spain) boundary layer from September to October 2010 (30 days) in the framework of the SAPUSS (Solving Aerosol Problems by Using Synergistic Strategies) field campaign. Two near-infrared ceilometers (Jenoptik CHM15K), vertically and horizontally probing (only vertical profiles are herein discussed), were deployed. Ceilometer-based DRCLs (1761 ± 363 m a.g.l.) averaged over the campaign duration were twice as high as the mean SML (904 ± 273 m a.g.l.). Both DRCL and SML showed a marked SML diurnal cycle. Ceilometer data were compared with potential temperature profiles measured by daily radiosounding (twice a day, midnight and midday) to interpret the boundary layer structure in the coastal urban area of Barcelona. The overall agreement (R2 = 0.80) between the ceilometer-retrieved and radiosounding-based SML heights (h) revealed overestimation of the SML by the ceilometer (Δh =145 ± 145 m). After separating the data in accordance with different atmospheric scenarios, the lowest SML (736 ± 183 m) and DRCL (1573 ± 428 m) were recorded during warm North African (NAF) advected air mass. By contrast, higher SML and DRCL were observed during stagnant Regional (REG) (911 ± 234 m and 1769 ± 314 m, respectively) and cold Atlantic (ATL) (965 ± 222 m and 1878 ± 290 m, respectively) air masses. In addition to being the lowest, the SML during the NAF scenario frequently showed a flat upper boundary throughout the day possibly because of the strong winds from the Mediterranean Sea limiting the midday SML convective growth. The mean backscatter coefficients were calculated at two selected heights representative of middle and top SML portions, i.e. β500 = 0.59 ± 0.45 Mm-1 sr-1 and β800 = 0.87 ± 0.68 Mm-1 sr-1 at 500 m and 800 m a.g.l., respectively. The highest backscatter coefficients were observed during NAF (β500 = 0.77 ± 0.57 Mm-1 sr-1) when compared with ATL (β500 = 0.51 ± 0.44 Mm-1 sr-1) and REG (β500 = 0.64 ± 0.39 Mm-1 sr-1). The relationship between the vertical change in backscatter coefficient and atmospheric stability (∂θ/∂z) was investigated in the first 3000 m a.g.l., aiming to study how the unstable, stable or neutral atmospheric conditions of the atmosphere alter the distribution of aerosol backscatter with height over Barcelona. A positive correlation between unstable conditions and enhanced backscatter and vice versa was found. © Author(s) 2013. Source

Ebermann M.,InfraTec GmbH | Neumann N.,InfraTec GmbH | Hiller K.,TU Chemnitz | Gittler E.,Systeme GmbH | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

First results of a MEMS Fabry-Perot filter (FPF) for the spectral range of 8-11 μm are presented. Broad bandwidth and a low phase dispersion could be achieved by using new dielectric materials with an enhanced refractive index contrast and relatively simple reflector designs with a low number of layers. Different designs of the Bragg reflectors and complete FPF devices have been developed and samples have been fabricated and tested. Especially tilting and in certain cases bowing of the reflectors lowers the finesse of the fabricated filters. The bandwidth of the FPF is in the range of 170- 250 nm and the peak transmittance has been determined to be up to 60 %. Simulation and measurements agree very well if the effect of the defective finesse is taken into considerations. © 2010 Copyright SPIE - The International Society for Optical Engineering. Source

Stolberg K.,Systeme GmbH | Friedel S.,Systeme GmbH | Kremser B.,Systeme GmbH | Leitner M.,Systeme GmbH | Atsuta Y.,Optopia Co.Ltd.
Journal of Laser Micro Nanoengineering | Year: 2010

This paper presents results of high-speed selective laser ablation of Silicon Nitride (SiN) coatings, which are used as antireflection and passivation layer at monocrystalline and multicrystalline silicon wafers for solar cells. We discuss ablation mechanism of NIR femtosecond laser pulses and advantages for cold ablation with minimised lattice damage. We show practical results of singleshot ablation with a repetition rate of 100 kHz. Finally we compare layer ablation with NIR picosecond laser. Source

Pawlowski E.,Schott AG | Kluge M.,Schott AG | Menke Y.,Schott AG | Peuchert U.,Schott AG | And 8 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Yb:YAG ceramic laser materials, fabricated by vacuum sintering technology, were optically investigated within different laser set-up configurations. The established nanopowder vacuum sintering process shows good potential for mass fabrication of multicomposite ceramic laser materials with different dopant concentrations. 5%, 7%, 10% single dopant and 7%/20% core-cladding multi-composite Yb:YAG materials were fabricated and investigated. The highest measured slope efficiency, for the composite ceramic laser materials was 81%, at 1030 nm emission wavelength, similar to Yb:YAG single crystals. © 2010 Copyright SPIE - The International Society for Optical Engineering. Source

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