24378 research outputs found
Sort by
Recipe optimization and SRF test of Cu compatible Nb3Sn films by DC magnetron sputtering from a stoichiometric target
No full textThe development of modern particle accelerators such as FCC ee requires improved energy efficiency. On the SRF cavity side, the intermetallic compound Nb3Sn is a promising alternative to niobium its higher critical temperature 18.3 K results into a BCS surface resistance at 4.5 K comparable to the one of Nb at 2 K, potentially allowing improved performance and reduced cryogenic costs while maintaining operation at 4.5 K. However, its brittleness makes bulk machining impractical, restricting its application to thin film coatings. This study presents Nb3Sn thin films deposited on copper substrates via DCMS using a single stoichiometric target. The optimization of the deposition parameters via the evaluation of the critical temperature, morphology, elemental composition and crystalline structure of the films is outlined. A niobium buffer layer is implemented to prevent copper tin interdiffusion, and plays a key role in the film quality. The results demonstrate Nb3Sn films deposited at amp; 8804; 650 C on copper substrates pre coated with a 30 amp; 956;m niobium buffer layer which exhibit a critical temperature amp; 8805; 17 K. The RF test of a film deposited via the same recipe on a bulk Nb QPR sample yielded an RF surface resistance of 23 n amp; 937; at 4.5 K, 20 mT and 400 MHz. These findings open the way to a scalable approach to high performance Nb3Sn Cu cavitie
High pressure synthesis and high performance half metallicity of quadruple perovskite oxide DyCu3Fe2Re2O12
No full textThe A and B site ordered quadruple perovskite oxide DyCu3 Fe 2 Re 2 O 12 with cubic Pn 3 symmetry was synthesized under high pressure and high temperature conditions. The material experiences a sharp long range ferrimagnetic transition arising from the strong superexchange antiferromagnetic interactions of Cu Re and Fe Re at a high Curie temperature TC amp; 8776; 660 K . Owing to the influence at lower temperatures of the antiferromagnetic ordering of the Dy3 occupying the A site, the susceptibility of DyCu3 Fe 2 Re 2 O 12 decreases continuously below 50 K, which is essentially different from that of the isostructural compound LaCu3 Fe 2 Re 2 O 12 . Moreover, in the presence of a magnetic field, the A site Dy3 spins are readily transformed into the ferromagnetic state from theantiferromagnetic ground state. Thus,the saturated magnetic moment of DyCu3 Fe 2 Re 2 O 12 is sharply enhanced from 7.0 amp; 956;B f.u. at 300 K to 14 amp; 956;B f.u. at 2 K by applying a magnetic field of 7 T. Theoretical calculations suggest that DyCu3 Fe 2 Re 2 O 12 is a half metallic ferrimagnet with a spin up band gap of approximately 2.0 eV. The combination of the high Curie temperature, wide half metallic energy gap, and large magnetic moment makes DyCu3 Fe 2 Re 2 O 12 promising for potential applications in advanced spintronic device
High Rate FA Based Co Evaporated Perovskites Understanding Rate Limitations and Practical Considerations to Overcome Their Impact
No full textSynchrotron Radiation for Quantum Technology
No full textIn recent years, quantum technology has undergone transformative advancements, opening up unprecedented possibilities in computation, metrology, sensing, and communication and reshaping the landscape of scientific research. Based on superposition, interference, and entanglement of quantum states, quantum systems leverage the core principles of quantum mechanics to achieve performances that were once deemed impossible or computationally insurmountable by classical methods. However, the practical realization of devices hinges on the conservation of these quantum states and their precise manipulation, requiring materials engineering with atomic precision on many length scales a formidable challenge. Synchrotron light and free electron laser FEL facilities, widely employed across diverse scientific and engineering disciplines, provide important single techniques and suites of multimodal non destructive imaging and diagnostic tools to reveal electronic, structural, and morphological properties of matter on device level. This article delves into how these tools can help to unlock the potential of quantum device technologies, overcoming production barriers and paving the way for future breakthroughs. Moreover, the article presents quantum optics in the x ray regime using synchrotron and FEL light sources and addresses the potential of quantum computing for synchrotron radiation experiment
How nanotextured interfaces influence the electronics in perovskite solar cells
No full textPerovskite solar cells have reached power conversion efficiencies that rival those of established silicon photovoltaics. Nanotextures in perovskite solar cells scatter the incident light, thereby improving optical absorption. In addition, experiments show that nanotextures impact electronic performance, although the underlying mechanisms remain unclear. This study investigates the underlying theoretical reasons by combining multi dimensional optical and charge transport simulations for a single junction perovskite solar cell. Our numerical results reveal that texturing redistributes the electric field, influencing carrier accumulation and recombination dynamics. We find that moderate texturing heights amp; 8804;300 nm always increase the power conversion efficiency, regardless of surface recombination velocities. Our study also clarifies why experiments have reported that texturing both increased and reduced open circuit voltages in perovskite solar cells this behaviour originates from variations in surface recombination at the untextured electron transport layer. In contrast, surface recombination at the textured hole transport layer strongly affects the short circuit current density, with lower recombination rates keeping it closer to the optical ideal. These findings provide new insights into the opto electronic advantages of texturing and offer guidance for the design of next generation textured perovskite based solar cells, light emitting diodes, and photodetector
Heterogenized Copper II Phenanthroline Catalysts for Electroreduction of CO2 to C2 Compounds Substitution on the Ligand Causes Structural Changes to the Molecular Framework and Stability Enhancement
No full textMolecular Cu catalysts have shown promise for electrochemical CO2 reduction eCO2RR to multi carbon products. Unlike metallic Cu facets, they offer precise control over the active site s electronic and steric configuration. However, prior studies identified critical challenges related to irreversible potential induced formation of Cu particles, which participate in the eCO2RR and obscure the role of molecular motifs. Based on a previously reported binuclear Cu II phenanthroline catalyst, a structurally modified second generation system with enhanced stability is developed. By introducing methoxy groups to the phenanthroline ligand, the molecular framework changes from a binuclear complex to an oligonuclear step like structure consisting of Cu II ions linked by 2 and 3 OH groups. When immobilized on a gas diffusion electrode, stable operation with a Faradaic efficiency of gt;70 for C2 products is achieved at elevated current densities. In situ XAS spectroscopy shows only negligible changes of the Cu coordination environment up to 50 mA cm amp; 8722;2. When approaching 250 mA cm amp; 8722;2, partial and reversible phase evolution occurs under Cu2 valence state reduction, followed by phase recovery upon bias removal. This system combines structural robustness with adaptive redox behavior, demonstrating a route for implementing molecular electrocatalysts in eCO2RR processes at industrial current densitie
Impact of metallographic polishing on the RF properties of Niobium for SRF applications
Full text linkThe performance of superconducting radio frequency SRF cavities made of niobium is tied to the quality of their inner surfaces exposed to the radio frequency RF waves. Future superconducting particle accelerators, because of their dimensions or the unprecedented stringent technical requirements, require the development of innovative surface processing techniques to improve processing reliability and if possible ecological footprint and cost, compared to conventional chemical processes. Metallographic polishing MP has emerged as a promising polishing technology to address these challenges. Previous studies focused on the characterization of the processed material surface at room temperature in the absence of RF waves. However, the evaluation of material properties, such as surface resistance under RF, at cryogenic temperature has failed, primarily due to the unavailability of devices capable of achieving the necessary resolution in the nanohm range. To overcome this limitation, a quadrupole resonator QPR has been utilized. The RF results demonstrate that the MP polishing, developed to preserve a high quality niobium surface with very low surface resistance, is highly effective compared to conventional polishing. This conclusion is further supported by topography and microstructural analysis of the QPR top hat samples, which revealed the clear superiority of the metallographic approac
Photoinduced Electron Transfer Across Phospholipid Bilayers in Anaerobic and Aerobic Atmospheres
Full text linkIn natural photosynthesis, light driven electron transfer across the thylakoid membrane enables efficient charge separation and the confinement of reaction spaces for generating NADPH and CO2 and oxidation of water. These reactions are complementary redox reactions and require different reaction conditions for optimal performance. However, current artificial photosynthesis studies only take place in the bulk and are sensitive toward oxygen and air, which limits their applicability under aerated and water splitting conditions. Herein, we report light driven electron transfer across a lipid bilayer membrane of liposome vesicles via a rigid oligoaromatic molecular wire that allows to electronically connect an oxidation and reduction reaction which are spatially separated by the membrane. The molecular wire has a simple, symmetric, easy to synthesize design based on benzothiadiazole and fluorene units and absorbs in the visible spectrum which makes it suitable for solar energy conversion. The model reactions in this study are light driven NADH oxidation on one side of the membrane and light driven reduction of an organic water soluble dye in the bulk phase of liposomes. Additionally, the system is active in both aerobic and anaerobic atmospheres, rendering it ideal for aerobic conditions or reactions that produce oxygen such as solar driven water splitting and artificial photosynthesis application
Converting Li Rich Layered Oxide Cathode into Non Shrinking Sacrificial Prelithiation Agent
No full textThe macromolecular crystallography beamlines of the Helmholtz Zentrum Berlin at the BESSY II storage ring history, current status and future directions
Full text linkSince 2003, the Macromolecular Crystallography MX group at Helmholtz Zentrum Berlin HZB has been operating three MX beamlines at the BESSY II storage ring in Berlin. These beamlines were established to support the emerging structural genomics initiatives founded in Germany, Europe, and overseas around the turn of the century. Over the past two decades, these beamlines have been continuously developed to enable state of the art diffraction experiments and to provide supporting facilities such as a sample preparation laboratory, a spectroscopy laboratory, a Biosafety Level 1 laboratory and all necessary computing resources for the MX and chemical crystallography user community. Currently, more than 100 independent research groups from the greater Berlin area, Germany, and Europe utilize these beamlines. Over time, more than 4500 Protein Data Bank depositions have been accrued based on data collected at the beamlines. This paper presents historical aspects of the beamlines, their current status including their research output, and future direction