2,060 research outputs found

    Hypothesis test of the photon count distribution for dust discrimination in dynamic light scattering

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    Users of dynamic light scattering (DLS) are challenged when a sample of nanoparticles (NPs) contains dust. This is a frequently inevitable scenario and a major problem that critically affects the reproducibility and accuracy of DLS measurements. Current methods approach this problem via photon correlation spectroscopy, but remedy exists only for a few special cases. We introduce here a general criterion and a clearly defined measure to discriminate between NPs and dust particles. The experimental results show that, in contrast to photon correlation spectroscopy, hypothesis testing and the statistical moment analysis of the photon count distribution provides an accurate and precise way to characterize NPs and Brownian dynamics in the presence of dust. To demonstrate, analyses of silica, iron oxide, and gold NPs of low polydispersity are presented

    Performance specifications for a meteorological satellite lidar Final report

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    Cirrus cloud cover observation capability and performance specifications for meteorological satellite lida

    Background and sensitivity studies for the LUX-ZEPLIN dark matter experiment

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    The existence of dark matter is now supported by a wide range of physical observations, ranging from galactic to cosmological scales. Our cosmological models predict dark matter to make up approximately 85% of the matter-content of the universe. One of the leading particle candidates that can effectively explain cosmological observations is the Weakly Interacting Massive Particles (WIMPS), the presence of which can be directly searched for by rare-event underground experiments via its scattering off atomic nuclei. By deploying a multi-tonne dual-phase liquid xenon (LXe) detector, the LUX-ZEPLIN (LZ) experiment, currently under construction in the Davis Campus at the Sanford Underground Research Facility (SURF) (South Dakota, USA) is projected to reach unprecedented sensitivities in search for WIMPs. In probing deeper into the WIMP landscape, an extensive screening and cleanliness campaign was envisioned, selecting some of the most radio-pure material for the construction of LZ. This work highlights some of the cutting-edge techniques used in understanding and modelling a wide range of backgrounds, focusing primarily on measuring and modeling the radon emanation background projections. By using the LZ simulation and statistical inference frameworks, the impact of radon emanation across different background scenarios are examined, where the 90% CL sensitivity is determined to vary from a cross-section of 1.34x10^{-48} cm^{2} to 1.76x10^{-48} cm^2 at best and worst case radon activities of 11.0 mBq and 60.4 mBq for a 40 GeV/c^{2}, respectively—remaining well below LZ requirement of 3.0x10^{-48} cm^{2}. The projected LZ sensitivity for a WIMP mass of 40 GeV/c^{2}, at a 90% CL and the 3 discovery potential was determined to be 1.43x10^{-48} cm^{2} and 3.4x10^{-48} cm^{2}. The projected limits from second-generation detectors, such as LZ and XENONnT, leave a significant amount of the parameter space above the cosmic neutrino floor (~10^{-49} cm^{2}) unexplored. In envisioning what a future third-generation (G3) detector may offer and the background necessities of such a detector, a toy G3 experiment is presented. A cryogenic radon facility currently under construction is outlined to pave the way for achieving the background requirements of a G3 dual-phase LXe observatory

    LUX-ZEPLIN (LZ) Technical Design Report

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    In this Technical Design Report (TDR) we describe the LZ detector to be built at the Sanford Underground Research Facility (SURF). The LZ dark matter experiment is designed to achieve sensitivity to a WIMP-nucleon spin-independent cross section of three times ten to the negative forty-eighth square centimeters

    The Sudbury Neutrino Observatory

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    The Sudbury Neutrino Observatory is a second generation water Cherenkov detector designed to determine whether the currently observed solar neutrino deficit is a result of neutrino oscillations. The detector is unique in its use of D2O as a detection medium, permitting it to make a solar model-independent test of the neutrino oscillation hypothesis by comparison of the charged- and neutral-current interaction rates. In this paper the physical properties, construction, and preliminary operation of the Sudbury Neutrino Observatory are described. Data and predicted operating parameters are provided whenever possible.Comment: 58 pages, 12 figures, submitted to Nucl. Inst. Meth. Uses elsart and epsf style files. For additional information about SNO see http://www.sno.phy.queensu.ca . This version has some new reference

    Dynamic Light Scattering for the Characterization of Polydisperse Fractal Systems by the Example of Pyrogenic Silica

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    Dynamic light scattering (DLS) is a method to size submicron particles by measuring their thermal motion (diffusion) in suspensions and emulsions. However, the validity of the Stokes-Einstein equation that relates the diffusion coefficient and the particle size is limited to spherical particles and very low concentrations. Within this thesis, DLS is used for the characterization of suspensions of pyrogenic silica which consists of fractal-like aggregates composed of sintered spherical primary particles. These structural features clearly complicate the understanding of DLS experiments and have been a severe obstacle to employing DLS as routine standard tool for the characterization of pyrogenic silica. The main objective of this thesis is therefore to evaluate the application of DLS in product development and quality assurance of pyrogenic silica industry, what essentially means to identify those structural properties of fractal aggregates which are measurable with DLS and to quantify the method’s sensitivity to changes in these properties. The investigations presented here are split up into four parts, simulations that establish a relation between structural and hydrodynamic properties, experiments validating the simulation results, the characterization of concentrated suspensions and the application-oriented analysis of DLS data for specific industrially relevant measurement tasks.Die Dynamische Lichtstreuung (DLS) ist eine Messmethode zur Größenbestimmung submikroner Partikel. Dabei wird primär die stochastische Bewegung der Teilchen (Diffusion) in Suspensionen und Emulsionen bewertet. Die Stokes-Einstein Gleichung, die das Verhältnis zwischen gemessenem Diffusionskoeffizienten und Partikelgröße wiedergibt, ist jedoch nur für kugelförmige Teilchen, die in sehr niedriger Konzentration vorliegen, gültig. In der vorliegenden Arbeit wird die dynamische Lichtstreuung zur Charakterisierung von Suspensionen pyrogener Kieselsäure eingesetzt. Diese besteht aus fraktalen Aggregaten, die wiederum aus versinterten aber meist kugelförmigen Primärpartikeln zusammengesetzt sind. Diese strukturellen Eigenschaften erschweren die Anwendbarkeit der DLS bzw. die Interpretation der Messergebnisse und verhinderten bisher den Einsatz der DLS als Routinemethode zur Charakterisierung pyrogener Kieselsäuren. Das Hauptziel dieser Arbeit ist daher eine Bewertung der Möglichkeiten der DLS für die Produktentwicklung und Qualitätssicherung in der Herstellung pyrogener Kieselsäuren. Das bedeutet im Besonderen, dass sowohl die messbaren granulometrischen Eigenschaften als auch die Sensitivität der Methode bei Eigenschaftsänderungen ermittelt werden müssen. Die hier durchgeführten Arbeiten sind in vier Teile gegliedert: Simulationen, die eine Beziehung zwischen strukturellen und hydrodynamischen Eigenschaften herstellen, Experimente zur Validierung der Simulationsergebnisse, die Charakterisierung konzentrierter Suspensionen und die anwendungsorientierte Auswertung von DLS-Daten für spezifische industrierelevante Messaufgaben
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