24378 research outputs found
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Kryogene Infrastruktur bei BESSY II Bestand und Ausblick
No full textDas Helmholtz Zentrum Berlin betreibt am Standort Adlershof u.a. den Elektronenspeicherring BESSY II. Für die Versorgung der im Speicherring installierten supraleitenden Wellenlängenschieber mit Flüssighelium ist ein He liumverflüssiger installiert. Ein weiterer Verflüssiger, inklusive umfassender kryogener Infrastruktur, versorgt mehrere Teststände, vor allem für supraleitende Hohlraumresonatoren, mit Helium bei 1,8 K. Neben dem Betrieb der existierenden Anlagen wird derzeit ein neuartiger Beschleunigertyp im Rahmen des Pro jektes bERLinPro aufgebaut. Um die benötigte Versorgung mit Flüssighelium zu gewährleisten, wird einer der bestehenden Heliumverflüssiger umgezogen sowie die Anlage um u.a. einen 10.000 l Dewar, drei Ventilboxen, eine Kaltkompressorbox, einen warmen Pumpstand und ein 80 K Helium System erweitert. Au erdem ist für das Zukunftsprojekt BESSY VSR, einer Weiterentwicklung des Speicherrings BESSY II, die Be schaffung einer dritten Kälteanlage geplant. Eine Herausforderung hierbei wird der ganzjährig durchgängige Be trieb sein. In diesem Papier wird der Aufbau der oben beschriebenen Anlagen detaillierter erläutert und ein Einblick in die Herausforderungen bei der Anlagenplanung gegeben. Abschlie end werden die geplanten zukünftigen Erweite rungen skizzier
Thermal Management of Solar Modules with Infrared Antireflective Coatings
No full textInfrared antireflective coatings can help to reduce the operating temperature of PV modules. We estimate the temperature reduction for silicon PV modules for five locations in North America and the effect on the annual energy yiel
Tunneling spectroscopy of the spinon Kondo effect in one dimensional Mott insulators
No full textWe study the tunneling density of states TDOS in one dimensional 1D Mott insulators at energies below the charge gap. By employing nonlinear Luttinger liquid theory and density matrix renormalization group DMRG simulations, we predict that in the presence of a magnetic impurity at the boundary, characteristic Fermi edge singularity features can appear at subgap energies in the TDOS near the boundary. In contrast to the Kondo effect in a metal, these resonances are strongly asymmetric and of power law form. The power law exponent is universal and determined by the spinon Kondo effec
A Roadmap on Optics for Terawatt Scale Photovoltaics
No full textThe ongoing development of photovoltaics into terawatt scale poses a number of challenges where the optics and photonics communities can contribute. An international consortium recently compiled a roadmap that elaborates on these challenge
Elemental asymmetries of spin and electron dynamics in an insulating ferrimagnet
No full textNiFe2O4 has gained significant attention from the scientific community due to its potential applications in microwave integrated devices, magnetoelectric coupling heterostructures, and spintronic devices such as spin filters. In this work, we explore the element specific ultrafast dynamics of NiFe2O4 films grown on ZnGa2O4 and MgAl2O4 with different lattice mismatches. To examine the dynamics, we utilize the transverse magneto optical Kerr effect at the extreme ultraviolet XUV regime, which provides access to the Fe and Ni M edges. The demagnetization is almost concurrent with the pump pulse, suggesting that slower phonon based interactions are not crucial for the demagnetization. The reflectivity of the MAO sample is significantly higher than for the ZGO sample, which correlates well with the increased amount of free carriers. Furthermore, the reflectivity exhibits pronounced oscillations in both the Fe and Ni signals with a period of ?2.8?ps 0.36?THz . Notably, the onset of the oscillations of the Fe is delayed by about 0.2?0.5?ps with respect to the N
Ideal Molecular Sieving with a Dense MOF for Helium Upgrading with Highly Diffusion Selective Mixed Matrix Membranes
No full textHelium is one of the most critical resources of this planet, as it is a finite resource, cannot be produced from radioactive decay and escapes the atmosphere, while being extraordinarily important for high tech applications in research and medicine. A concept of using the dense metal organic framework MOF MIL 116 Ga as a molecular sieve specifically allowing diffusion of He is demonstrated. Incorporating up to 20 wt. MIL 116 Ga into polysulfone, a chemically stable, mechanically robust, and commercially available polymer, high performance mixed matrix membranes are fabricated and tested in gas permeation. The membranes reach He permeabilities up to 37.4. Barrer and He CH4 selectivity of 1190, mimicking He concentration of 4 of a natural gas reservoir. With increasing filler content, the permeability of He increases, while CH4 permeability decreases. Microstructural analysis of the MIL 116 Ga reveals that the crystals grew into druse like hollow crystals, highly beneficial for fast He permeability. CH4, N 2, and CO2 cannot enter the crystal, as proven by sorption experiments, providing high diffusional selectivity. Furthermore, polymer filler interactions are investigated by scanning electron microscopy and energy dispersive X ray spectroscopy demonstrating ideal compatibility. The performance is benchmarked to existing composite materials and polymers, where MIL 116 Ga formate stands out with extraordinary membrane performanc
Production of Metallic Foam Precursors Using Current Activated Pressure Assisted Densification
No full textThe production of metallic foams is influenced by many aspects. Among other factors, compaction plays an important role in the powder metallurgical production of foamable precursors. A powder compaction metallurgical method, known as current activated pressure assisted densification CAPAD , is applied to enhance the compaction of metal foam precursors. This method improves precursor quality by achieving higher density, lower electrical resistivity, and more uniform pore nucleation in the resulting foams. Changes in the microstructure, constituents distribution, and their influence on the foam nucleation and expansion behavior are investigated. Compared to traditional uniaxial hot pressing UHP methods, CAPAD operates at significantly lower pressures than UHP, reducing energy consumption and processing time. The reduced operational demands and improved material properties highlight CAPAD s potential as a cost effective and efficient alternative to conventional compaction technique
Experimental and environmental impact of early stage lithium recovery in lithium ion battery recycling
Full text linkIn December 2019, the European Union announced the Green Deal as a growth strategy to ensure a resourceefficient and competitive economy. Based on this, in 2023 targets for battery recycling were formulated in a regulation. It is imperative to enhance both the recovery rate and the quality of the material to comply with this regulatory requirement. Two hydrometallurgical battery recycling processes for black mass from lithium ion batteries with nickel manganese cobalt oxide 111 have been examined. The experimental investigation focuses on comparing early stage lithium recovery ESLR process route, were lithium is leached in a first step with water from the black mass before acid leaching, with a reference route. Based on this analysis, an initial process simulation was developed in HSC SIM to generate data for life cycle assessment. Results show that the ESLR route increases lithium recovery to 61.9 in experiments, with higher product quality. Simulation based analysis showed a 5.7 reduction in climate change impact per kg black mass treated compared to the reference route. Improved lithium recovery and quality reduced the climate impact of secondary lithium carbonate by 16 , and by 37 if wind power replaces grid electricity. Among sixteen impact categories evaluated, the ESLR route has lower impacts than the reference in thirteen categorie
Origin of surface induced visible light absorption of nanostructured diamond
Full text linkSurface nanotextured diamond, named black diamond, absorbs efficiently visible light. This feature allows this material to be used in solar devices, such as the p i n photocathode under study in this work. Using optical and x ray surface sensitive spectroscopy techniques, this study establishes a correlation between the material s optical properties and its chemical structure to elucidate the nature of light absorption and photocarriers generation. The analysis reveals that the surface states in the very first atomic layer of the diamond, such as carbon sp2 reconstruction states and carbon oxygen bounds at 1.25 and 2.5 eV with respect to the maximum of the valence band, respectively, are the key factors for the enhancement of the visible light absorption with respect to pristine samples. These defects, together with a collective effect induced by the diffraction light trapping, could be useful for using black diamond in solar applications by exploiting the increase in the visible light absorptio