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Correlated X-ray Ptychography and Fluorescence Nano-Tomography on the Fragmentation Behavior of an Individual Catalyst Particle during the Early Stages of Olefin Polymerization
No full textA combination of X-ray ptychography and X-ray fluorescence tomography (XRF) has been used to study the fragmentation behavior of an individual Ziegler–Natta catalyst particle, ∼40 μm in diameter, in the early stages of propylene polymerization with submicron spatial resolution. The electron density signal obtained from X-ray ptychography gives the composite phases of the Ziegler–Natta catalyst particle fragments and isotactic polypropylene, while 3-D XRF visualizes multiple isolated clusters, rich in Ti, of several microns in size. The radial distribution of Ti species throughout the polymer–catalyst composite particle shows that the continuous bisection fragmentation model is the main contributor to the fragmentation pathway of the catalyst particle as a whole. Furthermore, within the largest Ti clusters the fragmentation pathway was found to occur through both the continuous bisection and layer-by-layer models. The fragmentation behavior of polyolefin catalysts was for the first time visualized in 3-D by directly imaging and correlating the distribution of the Ti species to the polymer–catalyst composite phase
110. Tagung der Studiengruppe elektronische Instrumentierung im Frühjahr 2019
No full textElektronik und Firm-/Software wird mit spezialisierten Anforderungen in vielen For-schungsprojekten benötigt. So haben viele Forschungszentren und auch Univer-sitäten Entwicklungsgruppen, die sich diesen Aufgaben stellen. Auch gibt es In-dustriebetriebe, die spezialisierte Beiträge beisteuern. Mit der Idee, dass man indiesem Umfeld von einander profitieren und zusammenarbeiten kann, treffen sichjedes Jahr einmal Techniker/-innen, Ingenieure/-innen und Wissenschaftler/-innen,um sich mit Vorträgen, einer Ausstellung und Gesprächen auszutauschen. Organ-isiert wird die Tagung von den Helmholtz-Zentren, offen für andere Vortragende undTeilnehmer/innen. Dieses Jahr war das ZEA-2, Systemhaus fur die Forschung, amForschungszentrum FZJ in Jülich der Gastgeber.Es waren sechs Helmholtz-Zentren, DESY, FZJ, GSI, HZG, HZDR und KIT, vertreten.Daneben nutzten Universitätsvertreter/innen die Gelegenheit des Austausches. DieIndustrie präsentierte auf High-End Anwendungen spezialisierte Geräte und warenfür viele Fachgespräche offen.Die Thematiken der Tagung umfassten:- Schnelle Datenaufnahme, -verarbeitung und -übertragung- ASIC's zu Datenübertragung und spezifischer Messsignalaufbereitung.- Kontrolle von Aktoren und Auslese langsamerer Sensoren- Fertigung von Elektronik und Geräten mit Elektronik- Kooperation zu Entwicklungen mit der Industrie- Wie testet man Elektronik und Firm-/Software?An einem halben Tag wurde ein Technikbetrieb zur Papierverarbeitung besichtigt.Auch da wurde gezeigt, dass die Steuerung von Maschinen anspruchsvoll ist und teilsähnliche Aspekte wie die Steuerung der Forschungsanlage aufweist.Das Tagungsprogramm ist auf dem Internet einzusehen:https://indico.desy.de/indico/event/22503/ oderhttps://indico.desy.de//event/SEI 2019Die Homepage der Studiengruppe ist auf http://sei.desy.de/ zu finden.Ein Workshop über "Testen" diente dem Austausch, wie man sich zum einen derVielfalt der spezialisierten Geräte effizient stellt und spezifische Eigenschaften im Testerfasst, und zum anderen doch von Wiederverwendbarkeit und Standards profitiert
Thermo-electrical modelling of the ATLAS ITk Strip Detector
No full textIn this paper we discuss the use of linked thermal and electrical network models to predict the behaviour of a complex silicon detector system. We use the silicon strip detector for the ATLAS Phase-II upgrade to demonstrate the application of such a model and its performance. With this example, a thermo-electrical model is used to test design choices, validate specifications, predict key operational parameters such as cooling system requirements, and optimize operational aspects like the temperature profile over the lifetime of the experiment. The model can reveal insights into the interplay of conditions and components in the silicon module, and it is a valuable tool for estimating the headroom to thermal runaway, all with very moderate computational effort
Boron Concentration Induced Co-Ta-B Composite Formation Observed in the Transition from Metallic to Covalent Glasses
No full textDue to their unique property combination of high strength and toughness, metallic glassesare promising materials for structural applications. As the behaviour of metallic glasses depends on theelectronic structure which in turn is defined by chemical composition, we systematically investigate theinfluence of B concentration on glass transition, topology, magnetism, and bonding for B concentrationsx = 2 to 92 at.% in the (Co6.8+-3.9Ta)100-xBx system. From an electronic structure and coordination pointof view, the B concentration range is divided into three regions: Below 39 +- 5 at.% B, the materialis a metallic glass due to the dominance of metallic bonds. Above 69 +- 6 at.%, the presence ofan icosahedra-like B network is observed. As the B concentration is increased above 39 +- 5 at.%,the B network evolves while the metallic coordination of the material decreases until the B concentrationof 67 +- 5 at.% is reached. Hence, a composite is formed. It is evident that, based on the B concentration,the ratio of metallic bonding to icosahedral bonding in the composite can be controlled. It is proposedthat, by tuning the coordination in the composite region, glassy materials with defined plasticity andprocessability can be designed
Intense Reactivity in Sulfur–Hydrogen Mixtures at High Pressure under X-ray Irradiation
No full textSuperconductivity near room temperature in the sulfur–hydrogen system arises from a sequence of reactions at high pressures, with X-ray diffraction experiments playing a central role in understanding these chemical–structural transformations and the corresponding S:H stoichiometry. Here we document X-ray irradiation acting as both a probe and as a driver of chemical reaction in this dense hydride system. We observe a reaction between molecular hydrogen (H2) and elemental sulfur (S8) under high pressure, induced directly by X-ray illumination, at photon energies of 12 keV using a free electron laser. The rapid synthesis of hydrogen sulfide (H2S) at 0.3 GPa was confirmed by optical observations, spectroscopic measurements, and microstructural changes detected by X-ray diffraction. These results document X-ray induced chemical synthesis of superconductor-forming dense hydrides, revealing an alternative production strategy and confirming the disruptive nature of X-ray exposure in studies on high-pressure hydrogen chalcogenides, from water to high-temperature superconductors
Detecting gravitational waves from cosmological phase transitions with LISA: an update
No full textWe investigate the potential for observing gravitational waves from cosmological phase transitions with LISA in light of recent theoretical and experimental developments. Our analysis is based on current state-of-the-art simulations of sound waves in the cosmic fluid after the phase transition completes. We discuss the various sources of gravitational radiation, the underlying parameters describing the phase transition and a variety of viable particle physics models in this context, clarifying common misconceptions that appear in the literature and identifying open questions requiring future study. We also present a web-based tool, PTPlot, that allows users to obtain up-to-date detection prospects for a given set of phase transition parameters at LISA
Study of central exclusive production in proton-proton collisions at 5.02 and 13 TeV
No full textCentral exclusive production of pairs is measured with the CMS detector in proton-proton collisions at the LHC at center-of-mass energies of 5.02 and 13 TeV. The theoretical description of these nonperturbative processes, which have not yet been measured in detail at the LHC, poses a significant challenge to models. The two pions are measured and identified in the CMS silicon tracker based on specific energy loss, whereas the absence of other particles is ensured by calorimeter information. The total and differential cross sections of exclusive central production are measured as functions of invariant mass, transverse momentum, and rapidity of the system in the fiducial region defined as transverse momentum 0.2 GeV and pseudorapidity 2.4. The production cross sections for the four resonant channels f, , f, and f are extracted using a simple model. These results represent the first measurement of this process at the LHC collision energies of 5.02 and 13 TeV
Search for lepton flavour violating decays of a neutral heavy Higgs boson to and e in proton-proton collisions at 13 TeV
No full textA search for lepton flavour violating decays of a neutral non-standard-model Higgs boson in the μτ and eτ decay modes is presented. The search is based on proton-proton collisions at a center of mass energy = 13 TeV collected with the CMS detector in 2016, corresponding to an integrated luminosity of 35.9 fb. The τ leptons are reconstructed in the leptonic and hadronic decay modes. No signal is observed in the mass range 200–900 GeV. At 95% confidence level, the observed (expected) upper limits on the production cross section multiplied by the branching fraction vary from 51.9 (57.4) fb to 1.6 (2.1) fb for the μτ and from 94.1 (91.6) fb to 2.3 (2.3) fb for the eτ decay modes.[graphic not available: see fulltext
Measurement of the and polarizations in proton-proton collisions at 8 TeV
No full textThe polarizations of promptly produced χc1 and χc2 mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at s=8 TeV. The χc states are reconstructed via their radiative decays χc→J/ψγ, with the photons being measured through conversions to e+e−, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χc2 to χc1 yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ→μ+μ- decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum