Download or read book The LZ Dark Matter Search and Development of a New Gas Phase Technique to Characterize Low Level Electron Emission from Electrode Grids written by Wei Ji and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dark Matter is needed to explain many cosmological observations and therefore has been proposed for many decades, but it awaits direct detection. One of the most popular classes of dark matter candidates is Weakly Interacting Massive Particles (WIMPs), which have masses in the order of 100 GeV and couple to ordinary matter at weak scale. In WIMP direct detection experiments, we look for WIMPs being scattered by nuclei, a process which produces low energy (smaller than 100 keV) recoiling nuclei that can be observed. We are building LZ, a detector looking for WIMPs using liquid xenon in a dual-phase time projection chamber (TPC), at 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. LZ aims to achieve the world's highest sensitivity to find WIMPs via WIMP-nucleon interactions. After a brief discussion of dark matter and the LZ experiment, this dissertation presents the details of my study to solve the electron emission problem. The LZ TPC will consist of electrode grids and other metallic surfaces that can emit electrons when operated under voltage. Because the charge measurement in the LZ detector is sensitive to single electrons, electrons from the grids can be both a significant nuisance for data collection and a source of background at low-energies, limiting the sensitivity of the experiment for low-mass WIMPs. This has motivated us to develop a test detector to study how to reduce this background. The test detector consists of a pair of grids biased to high voltage and operated in xenon gas. The electric field between the grid causes the electrons to produce electroluminescence scintillation light that is measured by PMTs. This new technique is sensitive to single electrons emitted by the grids, allowing a measurement of emission currents as low as atto-amperes. We used this detector to study the properties of different grids and to determine what treatments can be done to reduce their electron emission. We found that passivation with citric acid reduces electron emission from stainless steel surfaces. This work was supervised by Professor Thomas Shutt and was completed in collaboration with members of the LZ collaboration and the SLAC LZ group.
Download or read book The LZ Dark Matter Experiment written by Kelly M Stifter and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to a compelling body of astrophysical and cosmological evidence, dark matter has come to be accepted as a crucial ingredient of modern cosmology, yet its physical nature remains one of the most pressing questions in the field of physics. One historically favored model of dark matter is weakly interacting massive particles, or WIMPs. LUX-ZEPLIN (LZ) is a next-generation dark matter detector designed to achieve field-leading sensitivity to much of the remaining accessible parameter space within the WIMP dark matter paradigm. To help realize the full-scale LZ detector, the System Test R&D platform was constructed at SLAC National Accelerator Laboratory to validate the performance of critical LZ subsystems at scales approaching or comparable to the LZ design. In this dissertation, I present results showing that the passivation of the high voltage electrodes in citric acid leads to a significant reduction in spontaneous emission of single electrons, potentially limiting a major instrumental background by up to several orders of magnitude and enabling a more sensitive dark matter search. The LZ detector has now been assembled at the Sanford Underground Research Facility (SURF) in Lead, South Dakota and is taking early data. I also give a first look at commissioning data that captured the first light from electrons in the LZ detector, and share methods to validate the in situ performance of the high voltage electrodes.
Download or read book Background Modeling and First Searches for Low Energy Signals in The LUX ZEPLIN LZ Dark Matter Experiment written by Daniel Kodroff and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past half-century overwhelming evidence has mounted indicating the existence of a non-baryonic and enigmatic dark matter that constitutes approximately 85% of the total matter in the universe. Among the potential dark matter detection methods, dual- phase time projection chambers (TPCs) have emerged as the leading detector technology. LUX-ZEPLIN (LZ) is a direct detection dark matter experiment located at the 4850-ft depth level of the Sanford Underground Research Facility in South Dakota, USA, employing a 7 tonne active volume of liquid xenon in a dual-phase TPC. It's surrounded by an instrumented xenon "Skin" region and gadolinium-loaded liquid-scintillator outer detector, primarily serving as active vetoes for gamma-ray and neutron backgrounds, respectively, and contained within an ultra-pure water tank. The LZ detector began its first science run in December of 2021 and released its first results in the Summer of 2022. In order to ensure a low-background environment, a comprehensive material assay and selection campaign, for detector components, along with a xenon-purification campaign were pursued prior to and during construction. These mitigations have allowed LZ to achieve a background rate of 63.0 ± 4.5 x 10-6 events/keVee/kg/day in the low- energy region, approximately 60 times lower than that of its predecessor, the LUX experiment. LZ performed comprehensive measurements to constrain backgrounds in situ and construct a well-constrained time-dependent background model to use in searches for novel physics signals within this low-energy (
Download or read book Calibrations for the Improved Search for Dark Matter with the LZ LUX ZEPLIN Experiment written by Madan K. Sharma Timalsina and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A hypothetical non-luminous existence of matter is known as dark matter, inferred by the convincing collection of astrophysical and cosmological indirect evidence. In spite of compelling indirect observations, the physical nature of dark matter remains one of the most profound questions in the field of modern physics. A Weakly Interacting Massive Particle (WIMP) is historically the most favored candidate particle for dark matter, which could nicely explain the observed indirect measurements with the direct detection of WIMPs for the first time. The new second-generation direct detection dark matter experiment LZ (LUXZEPLIN), designed for direct detection of WIMP dark matter, has performed the most sensitive search for spin-independent WIMP-nucleon interactions. LZ is located 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. LZ is employing a two-phase xenon detector with an active mass of 7 tonnes. With LZ we have recently managed in the summer of 2022 to provide the most rigorous exclusion limit for spin-independent WIMP-nucleon scattering with an upper limit on the cross-section of 6.5×10−48 cm2 (90 % confidence level) for a WIMP mass of 30 GeV/c2 . The first WIMP search result of LZ utilizes a fiducial mass of 5.5 tonnes of liquid xenon and an exposure time of 60 live days. WIMPs could interact in the cryogenic liquid xenon of the detector’s core by scattering off xenon nuclei, which would then recoil and produce both scintillation light and electric charge. The ratio of the immediately detected scintillation light (S1) and the delayed charge detection (S2) is characteristic for such a nuclear recoil (NR) from hypothesized dark matter, e.g. a WIMP, and differs significantly from an electron recoil (ER) produced by undesired background reactions. However, the precise knowledge of the energy-dependent ratio S1/S2, for which the ER-dominated regime transitions into the NR-dominated regime, is key hereby to separate WIMP dark matter signals from unwanted background signals. We performed calibrations with neutron sources to map out the NR signal region for the WIMP search. Instead, gamma- and beta-ray calibration sources were utilized to map out the ER region, characteristic for background signals to be discriminated against. In this thesis, the calibration data to map out the NR signal region has been extensively studied and compared to the results of a full LZ detector simulation. In addition, another crucial detector calibration, for which all LZ data has to be corrected, is the purity monitoring of the liquid xenon. The chemical purity determines the lifetime of signal electrons against the absorption on impurities during their drift within the liquid xenon time projection chamber of the LZ detector. This electron lifetime analysis has been performed on a daily basis within the framework of this thesis and results have been applied by every data evaluator within the large LZ collaboration and for obtaining the current world’s best exclusion limit on WIMP dark matter.
Download or read book Characterizing the Peripheral Dynamics of Xenon Dark Matter Detectors written by Jacob Edward Cutter and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most important fundamental problems in physics today is to understand the nature of dark matter. The landscape of explanations for observed dark matter phenomena is vast and still expanding, and an impressive number of experiments have been built to probe the dark sector of the universe. A prominent class of detectors is aimed at discovering (or excluding) a particular kind of dark matter: the Weakly Interacting Massive Particle (WIMP). Searching for this popular dark matter candidate requires an ultra-sensitive, low-background target; xenon detectors serve as such a target for dark matter interactions. The Large Underground Xenon (LUX) detector is a dual-phase xenon time-projection chamber (TPC) which was operated underground at the Homestake Mine in Lead, South Dakota from 2013 to 2016, and was able to achieve the world's leading WIMP exclusion limit. However, successful reconstruction of WIMP-nucleus scatters in such detectors requires thorough understanding of the detection medium, which is made difficult by various confounding effects near the detector walls. Field-fringing is a major component of confusion in the periphery, and the large electric field non-uniformities in Run 4 of LUX provided a significant challenge in the dark matter analysis. Here is presented an algorithm to bijectively map between reconstructed event positions and true spatial coordinates, which serves as an important tool for studying field effects and fiducialization in LUX. Additionally, a successful dark matter search must model interfering background events in the WIMP search region which can't be directly vetoed. One class of unavoidable backgrounds comes from nuclear decay chain daughters in detector materials themselves, which may produce WIMP-like signals (an effect which is amplified due to various detector effects). The Davis Xenon (DAX) test bed system and a dual-phase TPC have been assembled and operated at UC Davis to characterize these common "wall backgrounds", as well as perform other R&D studies for the next-generation LUX-ZEPLIN (LZ) experiment. The DAX TPC specifically measures the xenon response to heavy nuclei produced by custom [alpha] decay sources created using novel chemical deposition procedures. In this thesis, results will be presented for the light and charge yields of immersed localized sources of 206Pb ions in liquid xenon, as well as a method for tagging such recoil events in situ by using PIN diodes as charged particle detectors to capture the correlated [alpha] particles. We also compare our isolated 206Pb events with previous WIMP search data from LUX, and discuss the significance of 206Pb as a WIMP background. Such information is most useful to future experiments if it can improve existing background models and simulations. The Noble Element Simulation Technique (NEST) is the ultimate software package for calculating expected signal yields in xenon detectors, but is an empirical framework that relies on experimental data to inform the models. We discuss the development of current NEST v2 models, specifically the heavy nuclear recoil models, as well as our current understanding of the xenon microphysics. We also show NEST predictions for mono-energetic 206Pb recoils, and discuss how our most recent DAX 206Pb measurements may inform NEST models in future work.
Download or read book Hydrogen Energy and Fuel Cells written by European Commission. Directorate General for Research and published by . This book was released on 2003 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Electrochemistry at Semiconductor and Oxidized Metal Electrodes written by S.R. Morrison and published by Springer. This book was released on 2011-10-12 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of the present volume is to develop the theory and practice of nonmetal electrochemistry from first principles, emphasizing energy level models, in particular the fluctuating energy level model of Marcus and Gerischer. A single volume emphasizing these models. and the in terpretation of experiments based on these models, has not been available. Yet this area of electrochemical technology, where the use of such models is required, has developed a great deal of interest. This is not only because of the interest in photoelectrochemical solar cells, but also because of the importance of the concepts in corrosion, sensors, coated metal electrodes, and, indeed, to the general theory of electrode reactions. This book is an attempt to fill the void-to develop in a single volume the basic description of electrode reactions on nonmetallic electrodes and oxide-covered metal electrodes. The development of the fluctuating energy level model to describe electrode reactions on nonmetals (as described in Chapters I through 3) has permitted a significant forward step in the understanding of such re actions. The power of the model is illustrated by the simple methods available to determine the energy levels of interest-the conduction and valence bands of the nonmetals (Chapter 5), and their relation to the energy levels of oxidizing or reducing agents in solution. In Chapter 6, we illustrate the ability of the simple models. based on these parameters, to describe successfully electrode reactions at an inert electrode.
Download or read book Physics at Surfaces written by Andrew Zangwill and published by Cambridge University Press. This book was released on 1988-03-24 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: Physics at Surfaces is a unique graduate-level introduction to the physics and chemical physics of solid surfaces, and atoms and molecules that interact with solid surfaces. A subject of keen scientific inquiry since the last century, surface physics emerged as an independent discipline only in the late 1960s as a result of the development of ultra-high vacuum technology and high speed digital computers. With these tools, reliable experimental measurements and theoretical calculations could at last be compared. Progress in the last decade has been truly striking. This volume provides a synthesis of the entire field of surface physics from the perspective of a modern condensed matter physicist with a healthy interest in chemical physics. The exposition intertwines experiment and theory whenever possible, although there is little detailed discussion of technique. This much-needed text will be invaluable to graduate students and researchers in condensed matter physics, physical chemistry and materials science working in, or taking graduate courses in, surface science.
Download or read book The Physics of Quantum Mechanics written by James Binney and published by Oxford University Press, USA. This book was released on 2013-12 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt: This title gives students a good understanding of how quantum mechanics describes the material world. The text stresses the continuity between the quantum world and the classical world, which is merely an approximation to the quantum world.
Download or read book Vanadium Dioxide Based Thermochromic Smart Windows written by Yi Long and published by CRC Press. This book was released on 2021-05-27 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: The usage of building energy accounts for 30–40% of total energy consumption in developed countries, exceeding the amount for industry or transportation. Around 50% energy for building services is contributed by heating, ventilation, and air-conditioning (HVAC) systems. More importantly, both building and HVAC energy consumptions are predicted to increase in the next two decades. Windows are considered as the least energy-efficient components of buildings. Therefore, smart windows are becoming increasingly important as they are capable of reducing HVAC energy usage by tuning the transmitted sunlight in a smart and favoured way: blocking solar irradiation on hot days, while letting it pass through on cold days. Compared with other type of smart windows, thermochromic windows have the unique advantages of cost-effectiveness, rational stimulus, and passive response. This book covers fabrication of vanadium dioxide–based smart windows, discusses various strategies to enhance their performance, and shares perspectives from the top scientists in this particular field.
Download or read book Photoneutron Sources written by B. W. Sargent and published by . This book was released on 1946 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book DNAPL Site Evaluation written by James W. Mercer and published by CRC-Press. This book was released on 1993-04-29 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: DNAPL Site Evaluation covers long-term contamination of ground water by DNAPL (dense non-aqueous phase liquids) chemicals. The book develops a framework for planning and implementing DNAPL site characterization activities. It provides detailed methods to identify, characterize, and monitor sites and analyzes their utility, limitations, risks, availability, and cost. Methods to interpret contaminant fate and transport are identified, and new site characterization methods are assessed. DNAPL Site Evaluation will maximize the cost-effectiveness of site investigation/remediation by providing the best information available to describe and evaluate methods to be used for determining the presence, fate, and transport of subsurface DNAPL contamination. The book will be a useful reference for groundwater professionals and environmental regulatory personnel.
Download or read book Physics of Low Dimensional Systems written by José L. Morán-López and published by Springer Science & Business Media. This book was released on 2001-05-31 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains contributions on some of the most important and current topics on the physics of low dimensional systems. The main emphasis is on the magnetic properties of surfaces, thin films, and atomic clusters. State-of-the-art techniques are discussed in detail. Techniques for the production and measurement of nanostructures are discussed, and pioneering contributions on the effect on health of these particles are presented. Important studies on semiconductor nanostructures are addressed as well as aerosol systems.
Download or read book Characterization of Solid Surfaces written by Philip F. Kane and published by Springer Science & Business Media. This book was released on 2013-11-27 with total page 675 pages. Available in PDF, EPUB and Kindle. Book excerpt: Until comparatively recently, trace analysis techniques were in general directed toward the determination of impurities in bulk materials. Methods were developed for very high relative sensitivity, and the values determined were average values. Sampling procedures were devised which eliminated the so-called sampling error. However, in the last decade or so, a number of developments have shown that, for many purposes, the distribution of defects within a material can confer important new properties on the material. Perhaps the most striking example of this is given by semiconductors; a whole new industry has emerged in barely twenty years based entirely on the controlled distribu tion of defects within what a few years before would have been regarded as a pure, homogeneous crystal. Other examples exist in biochemistry, metallurgy, polyiners and, of course, catalysis. In addition to this of the importance of distribution, there has also been a recognition growing awareness that physical defects are as important as chemical defects. (We are, of course, using the word defect to imply some dis continuity in the material, and not in any derogatory sense. ) This broadening of the field of interest led the Materials Advisory Board( I} to recommend a new definition for the discipline, "Materials Character ization," to encompass this wider concept of the determination of the structure and composition of materials. In characterizing a material, perhaps the most important special area of interest is the surface.
Download or read book National Semiconductor Metrology Program written by National Institute of Standards and Technology (U.S.) and published by . This book was released on 1995 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Springer Handbook of Electrochemical Energy written by Cornelia Breitkopf and published by Springer. This book was released on 2016-12-05 with total page 1019 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive handbook covers all fundamentals of electrochemistry for contemporary applications. It provides a rich presentation of related topics of electrochemistry with a clear focus on energy technologies. It covers all aspects of electrochemistry starting with theoretical concepts and basic laws of thermodynamics, non-equilibrium thermodynamics and multiscale modeling. It further gathers the basic experimental methods such as potentiometry, reference electrodes, ion-sensitive electrodes, voltammetry and amperometry. The contents cover subjects related to mass transport, the electric double layer, ohmic losses and experimentation affecting electrochemical reactions. These aspects of electrochemistry are especially examined in view of specific energy technologies including batteries, polymer electrolyte and biological fuel cells, electrochemical capacitors, electrochemical hydrogen production and photoelectrochemistry. Organized in six parts, the overall complexity of electrochemistry is presented and makes this handbook an authoritative reference and definitive source for advanced students, professionals and scientists particularly interested in industrial and energy applications.
Download or read book New Directions in Atomic Physics written by C.T. Whelan and published by Springer Science & Business Media. This book was released on 1999-09-30 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: The last few years have seen some remarkable advances in the understanding of atomic phenomena. It is now possible to isolate atomic systems in traps, measure in coincidence the fragments of collision processes, routinely produce, and study multicharged ions. One can look at bulk matter in such a way that the fundamental atomic character is clearly evident and work has begun to tease out the properties of anti matter. The papers in this book reflect many aspects of modem Atomic Physics. They correspond to the invited talks at a conference dedicated to the study of "New Directions in Atomic Physics," which took place in Magdalene College, Cambridge in July of 1998. The meeting was designed as a way of taking stock of what has been achieved and, it was hoped, as a means of stimulating new research in new areas, along new lines. Consequently, an effort was made to touch on as many directions as we could in the four days of the meeting. We included some talks which overviewed whole subfields, as well as quite a large number of research contributions. There is a unity to Physics and we tried to avoid any artificial division between theory and experiment. We had roughly the same number of talks from those who are primarily concerned with making measurements, and from those who spend their lives trying to develop the theory to describe the experiments.
