| 1. |
- Akkoyun, S., et al.
(författare)
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AGATA - Advanced GAmma Tracking Array
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002 .- 0167-5087 .- 1872-9576. ; 668, s. 26-58
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Tidskriftsartikel (refereegranskat)abstract
- The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation γ-ray spectrometer. AGATA is based on the technique of γ-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a γ ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of γ-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector- response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer. © 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Luoni, F., et al.
(författare)
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Total nuclear reaction cross-section database for radiation protection in space and heavy-ion therapy applications
- 2021
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 23:10
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Forskningsöversikt (refereegranskat)abstract
- Realistic nuclear reaction cross-section models are an essential ingredient of reliable heavy-ion transport codes. Such codes are used for risk evaluation of manned space exploration missions as well as for ion-beam therapy dose calculations and treatment planning. Therefore, in this study, a collection of total nuclear reaction cross-section data has been generated within a GSI-ESA-NASA collaboration. The database includes the experimentally measured total nucleus-nucleus reaction cross-sections. The Tripathi, Kox, Shen, Kox-Shen, and Hybrid-Kurotama models are systematically compared with the collected data. Details about the implementation of the models are given. Literature gaps are pointed out and considerations are made about which models fit best the existing data for the most relevant systems to radiation protection in space and heavy-ion therapy.
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| 4. |
- Wilken, Norman, 1983, et al.
(författare)
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Heat of adsorption for NH3, NO2 and NO on Cu-Beta zeolite using microcalorimeter for NH3 SCR applications
- 2010
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 151:3-4, s. 237-243
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Tidskriftsartikel (refereegranskat)abstract
- Microcalorimetry is a powerful technique with which to measure the heat of adsorption (Delta H), producing values that are very important when developing kinetic models. The method provides a way of determining these parameters independently. For kinetic models describing NH3 SCR it is critical to be able to accurately describe the storage of ammonia and NO in order to simulate rapid transients occurring in the experiments. The objective of our study is to measure the heat of adsorption of NH3, NO2 and NO on Cu-Beta. An ammonia TPD experiment was conducted at 150 degrees C using the microcalorimeter, resulting in the observation of an exotherm when introducing ammonia due to adsorption. This resulted in an average heat of adsorption of -100 kJ/mol. A good reproducibility was found when using a second sample, resulting in -97 kJ/mol. In order to investigate the coverage dependence of the heat of adsorption, an ammonia stepwise experiment was conducted. First, the catalyst was exposed to NH3 at 500 degrees C, resulting in the adsorption of strongly bound ammonia and obtaining a heat of adsorption of -110 kJ/mol. Thereafter, the catalyst was cooled in Ar and at 400 degrees C, NH3 was again introduced. Due to that the temperature is lower the ammonia that adsorbed was weaker. The procedure was repeated at 300, 200 and 100 degrees C, resulting in a coverage dependent activation energy for ammonia desorption (if assuming zero activation for adsorption) according to the following formula: E-desorption,NH3 = 120.0 (1 - 0.38 theta(NH3)) where theta(NH3) is the coverage of ammonia on the surface. The NO and NO2 adsorption and desorption were investigated using NO and NO2 TPD experiments, respectively. For the NO2 TPD experiment, approximately three NO2 were stored for each NO produced, corresponding to the disproportionation mechanism. This resulted in Delta H of -65 kJ/mol per NO2 consumed. The NO TPD experiment resulted in that only small amounts of NO was adsorbed. (C) 2010 Elsevier B.V. All rights reserved.
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| 5. |
- Wilken, Norman, 1983, et al.
(författare)
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The effect of accelerated hydrothermal aging on NH 3-SCR over Cu-Hbea catalyst
- 2011
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Ingår i: 11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings. - 9780816910700
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Konferensbidrag (refereegranskat)abstract
- Diesel engines have good fuel efficiency. However, the excess of oxygen that is fed into the engine is also present in the exhaust stream. This disables the selectivity of the standard three-way catalyst towards NO x. The influence of hydrothermal aging on the SCR mechanism was studied. A trend towards less strong bound ammonia for higher aging temperatures is observed, which agreed with TPD experiments. Ammonia SCR is an important technique for reducing NO x from diesel and lean burn gasoline engines. Zeolite based catalysts are a good choice for this reaction. However, they can be hydrothermally aged. This is an abstract of a paper presented at the 2011 AIChE Annual Meeting (Minneapolis, MN 10/16-21/2011).
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| 6. |
- Kazemahvazi, Sohrab, 1981-, et al.
(författare)
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Dynamic failure of clamped circular plates subjected to an underwater shock
- 2007
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Ingår i: Journal of Mechanics of Materials and Structures. - : Mathematical Sciences Publishers. - 1559-3959. ; 2:10, s. 2007-2023
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Tidskriftsartikel (refereegranskat)abstract
- Clamped circular copper plates have been subjected to exponentially decaying underwater blast waves with peak pressures in the range 10MPa to 300MPa and decay constants varying between 0.05ms to 1.1 ms. The deformation and failure modes were observed by high-speed photography. For the thin plates considered in this study, the failure modes were primarily governed by the peak pressures and were reasonably independent of the blast wave decay constant. Three modes of deformation and failure were identified. At low pressures, the plates undergo bending and stretching without rupture (mode I). At intermediate pressures a range of tensile tearing modes were observed, from petalling failures to tearing at the supports with increasing blast pressures. These tearing modes are referred to as mode II failures. At the highest pressures investigated here, the plate tears at the supports in a manner that is reminiscent of a shear-off failure. This failure is labeled as mode III. Scanning electron micrographs of the failure surfaces showed that in all cases, the local failure mechanism was tensile necking. Finite element (FE) simulations employing a local shear failure criterion are used to model the rupture of the material. Appropriately calibrated FE models capture all failure modes with sufficient fidelity.
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| 7. |
- Powell, John, et al.
(författare)
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The sensitivity of hybrid laser welding to variations in workpiece position
- 2011
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3892. ; 12:1, s. 188-193
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Tidskriftsartikel (refereegranskat)abstract
- High speed imaging has been used to analyze the sensitivity of the Hybrid laser welding process to variations in the laser-arcworkpiece geometry along the axis of the laser beam. The welding process was found to be stable within a certain range of workpiece positions. Outside of this range the process became unstable. If the workpiece was too close to the laser/arc combination, the two energy sources did not supplement each other sufficiently. If the workpiece was too far away the droplets from the arc interfered with the laser-keyhole interaction.
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| 8. |
- Schneider, J., et al.
(författare)
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Additive manufacturing of a metallic optical bench—process development, material qualification and demonstration
- 2023
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Ingår i: CEAS Space Journal. - : Springer Nature. - 1868-2502 .- 1868-2510. ; 15:1, s. 55-68
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Tidskriftsartikel (refereegranskat)abstract
- With the large-class science mission ATHENA, the European Space Agency (ESA) aims at exploring the hot and energetic universe with advanced X-Ray technology. As a central component of the telescope, hundreds of silicon pore optic (SPO) modules will be assembled in an optical bench with a diameter of about 2.5 m. Several approaches are under investigation for the manufacturing of this supporting structure, and for handling the challenging constraints with respect to size, geometry and material. In cooperation with ESA, the Fraunhofer IWS is currently investigating the manufacturing of the optical bench made from Ti-6Al-4 V by means of Additive Manufacturing using Laser Metal Deposition (LMD) followed by subtractive finishing. Several development steps have been covered in a holistic manner starting with the system engineering of the production site. The main focus of the activity was on the process development for the Additive Manufacturing as well as the subtractive finishing. Furthermore, the properties of the produced material were also investigated. Within the scope of this publication, a general overview is given about the project related developments, achievements, and flanking activities for solving various challenges. The suitability of the developed technologies and workflows are now being evaluated through the manufacture of a representative, large-scale breadboard.
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| 9. |
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| 10. |
- Wilken, Norman, 1983, et al.
(författare)
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Investigation of the Effect of Accelerated Hydrothermal Aging on the Cu Sites in a Cu-BEA Catalyst for NH3-SCR Applications
- 2013
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 56:1-8, s. 317-322
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Tidskriftsartikel (refereegranskat)abstract
- The influence of hydrothermal aging between 500 and 900 A degrees C for 3 h, on the structure of a Cu-Beta catalyst was studied in this work. The XRD measurements indicated a structural breakdown of the zeolite upon 900 A degrees C hydrothermal aging. This was confirmed from the loss of surface area as measured by BET method. The temperature for the zeolite structure break down was different between the powder bed as opposed to the sample that was washcoated on a cordierite monolith, which was most likely due to slightly different aging conditions and the presence of binders. The strong increase in the intensity of the Cu2p XPS peak indicated that the surface is enriched of copper at higher temperatures due to the zeolite structure collapse. The presence of CuO is usually accompanied by a satellite peak, which was clearly observed at higher binding energies for the catalysts aged at 800 and 900 A degrees C. The XPS results are in good agreement with the UV-Vis experiments, which also point to the formation of copper oxide after high temperature aging.
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