| 1. |
- Leopold, Tobias, et al.
(författare)
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Feasibility of photodetachment isobar suppression of WF5- with respect to HfF5
- 2014
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 359, s. 12-18
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Tidskriftsartikel (refereegranskat)abstract
- The feasibility of using laser photodetachment as a means for isobar suppression in accelerator mass spectrometry has been investigated for the special case of HfF5-/WF5-. A method for absolute photodetachrnent cross section measurements was applied and the cross sections of tungsten pentafluoride and hafnium pentafluoride negative ions were measured. The measurements indicate that the photodetachment cross section for WF5- is at least 100 times larger than for HfF5- at the wavelength of the fourth harmonic of the Nd:YAG laser at 266 nm. The absolute cross section for WF5- at this photon energy was found to be (2.8 +/- 0.3) x 10(-18) cm(2), while an upper limit of 2 x 10(-2) cm(2) was obtained for the HfF5- cross section. The measured cross sections indicate that an optical filtering scheme for isobar suppression in accelerator mass spectrometry for the case of Hf-182 should be feasible. (C) 2013 Elsevier B.V. All rights reserved.
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| 2. |
- Merlone, A., et al.
(författare)
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The MeteoMet project - metrology for meteorology: challenges and results
- 2015
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Ingår i: Meteorological Applications. - : Wiley. - 1350-4827 .- 1469-8080. ; 22, s. 820-829
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Tidskriftsartikel (refereegranskat)abstract
- The study describes significant outcomes of the Metrology for Meteorology' project, MeteoMet, which is an attempt to bridge the meteorological and metrological communities. The concept of traceability, an idea used in both fields but with a subtle difference in meaning, is at the heart of the project. For meteorology, a traceable measurement is the one that can be traced back to a particular instrument, time and location. From a metrological perspective, traceability further implies that the measurement can be traced back to a primary realization of the quantity being measured in terms of the base units of the International System of Units, the SI. These two perspectives reflect long-standing differences in culture and practice and this project - and this study - represents only the first step towards better communication between the two communities. The 3 year MeteoMet project was funded by the European Metrology Research Program (EMRP) and involved 18 European National Metrological Institutes, 3 universities and 35 collaborating stakeholders including national meteorology organizations, research institutes, universities, associations and instrument companies. The project brought a metrological perspective to several long-standing measurement problems in meteorology and climatology, varying from conventional ground-based measurements to those made in the upper atmosphere. It included development and testing of novel instrumentation as well as improved calibration procedures and facilities, instrument intercomparison under realistic conditions and best practice dissemination. Additionally, the validation of historical temperature data series with respect to measurement uncertainties and a methodology for recalculation of the values were included.
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| 4. |
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| 5. |
- da Silva, A. Ferreira, et al.
(författare)
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Growth, Electrical and Optical Properties of SnO2:F on ZnO, Si and Porous Si Structures
- 2009
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Ingår i: NANOTECH CONFERENCE & EXPO 2009, VOL 1, TECHNICAL PROCEEDINGS. - : CRC PRESS-TAYLOR & FRANCIS GROUP. - 9781439817827 ; , s. 352-
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Konferensbidrag (refereegranskat)abstract
- In this work we have analyzed the optical absorption of the ZnO and SnO2:F (FTO) films and applied them in porous silicon light-emitting diodes. The absorption and energy gap were calculated by employing the projector augmented wave method [1] within the local density approximation and with a modeled on-site self-interaction-like correction potential within the LDA+U-S/C [2]. Experiment and theory show a good agreement when the optical absorption and optical energy gap are considered. A layer of FTO is deposited by spray pyrolysis on top of porous Si (PSi) or ZnO/(PSi) in order to make the LEDs. The morphology and roughness of the films are analyzed by Atomic Force Microscopy before and after the FTO deposition. The electrical and optical properties are studied by characteristics curves J x V, and electroluminescence intensity versus bias.
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| 6. |
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| 7. |
- Ferreira Da Silva, A., et al.
(författare)
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Growth, optical characterization and modeling of ZnO nanorods on Si, SiC and macroporous si structure
- 2009
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Ingår i: Technical Proceedings of the 2009 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2009. - : CRC Press. - 9781439817834 - 9781439817841 ; , s. 206-209
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Konferensbidrag (refereegranskat)abstract
- Zinc Oxide (ZnO) and Silicon Carbide (SiC) are prominent materials with large applicability such as optoelectronic nanodevices and for instance ultraviolet detectors. There is lack of important information about optical transitions beyond the indirect band gap energy (BGE) of 4H-SÍC and even more for ZnO direct BGE grown on the former material. Using vapor-liquid-solid and the aqueous chemical growth methods we have grown ZnO nanorods on different substrates, such as quartz, n- and p-type porous silicon, and n-type 4H-SÍC. Scanning electron microscopy (SEM) was employed to compare sample morphologies. The absorption was calculated employing a projector augmented wave (PAW) method. The measured absorption of ZnO nanorods, on different substrates, is lower than that observed for ZnO films on quartz substrate, in the low energy spectral range. It is observed a strong effect of 4H-SÍC substrates on ZnO nanorod properties. Experiment and theory show a good agreement when the shape of the optical absorption is considered for both materials.
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| 8. |
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| 9. |
- Klason, Peter, et al.
(författare)
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A speed of sound based feed water temperature sensor
- 2012
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Ingår i: 9th International Temperature Symposium on Temperature. - : AIP. ; , s. 925-930
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Konferensbidrag (refereegranskat)abstract
- Controlling thermal power in the feed water line of a power plant presupposes both accurate flow and temperature measurement. In this application the temperature measurement is usually a single Pt-100. This results in a measurement error of several kelvin. In this study we have investigated two different sensors based on the speed of sound (SoS) in the flowing medium for measuring the average temperature across a flow pipe cross-section. This is a task within the on-going European research project called ENG-06. The two SoS-based temperature measuring sensors were investigated under laboratory conditions. Investigations were done using both homogenous and non-homogenous temperature distributions with temperature differences up to 25 K. In addition the influence of pressure (50-200 kPa) and flow rates (0.5-2 m/s) on the SoS devices were also investigated. Our results show that the SoS-based temperature principle is working. Furthermore, depending on the measurement conditions a SoS temperature measurement device significantly can reduce the deviation to the reference sensor compared with a single Pt-100 sensor. Relative reductions in the deviation to the reference of 20-85 % were possible to achieve. This opens for the possibility of increasing the energy efficiency in power plants as aimed for in the ENG-06 project.
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| 10. |
- Klason, P, et al.
(författare)
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Fabrication and characterization of p-Si/n-ZnO heterostructured junctions
- 2009
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Ingår i: MICROELECTRONICS JOURNAL. - : Elsevier BV. - 0026-2692. ; 40:4-5, s. 706-710
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Tidskriftsartikel (refereegranskat)abstract
- In this paper ZnO nanorods and nanodots (with and without a SiO2 buffer layer) were grown on p-Si, forming p-n heterojunctions. The nanorod devices showed no visible electroluminescence (EL) emission but showed rectifying behavior. Covering around 60% of the length of the nanorods with PMMA produced an ideality factor of 3.91 +/- 0.11 together with a reverse saturation current of 6.53 +/- 4.2 x 10(-8) A. Up to two orders of magnitude rectification was observed for the current at bias -3 and 3 V. The nanodot devices showed EL emission under forward bias conditions. It seems that the buffer layer increased both the stability and efficiency of the devices, since the buffer layer device could operate at larger applied voltage and showed EL emission under reverse bias.
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