Author: Adam BaileyPublisher:
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Category :
Languages : en
Pages :
Book Description
Dark Matter Searches and Study of Electrode Design in LUX and LZ.
Author: Adam BaileyThe LZ Dark Matter Experiment
Author: Kelly M StifterPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
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.
The LZ Dark Matter Search and Development of a New Gas Phase Technique to Characterize Low Level Electron Emission from Electrode Grids
Author: Wei JiPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
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.
Dark Matter Searches with the LUX and LZ Experiments
Author: Sally ShawDark Matter Searches with the LUX and LZ Experiments
Author: S. ShawExperimental High Energy Physics Research
Author: Publisher:
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Category :
Languages : en
Pages :
Book Description
The grant supported research on an experimental search for evidence of dark matter interactions with normal matter. The PI carried out the research as a member of the LUX and LZ collaborations. The LUX research team collected a first data set with the LUX experiment, a large liquid xenon detector installed in the Sanford Underground Research Facility (SURF). The first results were published in Physical Review Letters on March 4, 2014. The journal Nature named the LUX result a scientific highlight of the year for 2013. In addition, the LZ collaboration submitted the full proposal for the Lux Zeplin experiment, which has since been approved by DOE-HEP as a second-generation dark matter experiment. Witherell is the Level 2 manager for the Outer Detector System on the LUX-Zeplin experiment.
Calibrations for the Improved Search for Dark Matter with the LZ (LUX-ZEPLIN) Experiment
Author: Madan K. Sharma TimalsinaPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
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.
Characterizing the Peripheral Dynamics of Xenon Dark Matter Detectors
Author: Jacob Edward CutterPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
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.
The LUX Dark Matter Experiment
Author: Patrick PhelpsPublisher:
ISBN:
Category : Astrophysics
Languages : en
Pages : 191
Book Description
Dark matter, the mysterious substance that seems to make up most of the mass of the universe, has never been detected in the laboratory. In this document I outline the current world's leading experiment, LUX, to look for a class of dark matter, the Weakly Interacting Massive Particle. I outline the general principles of searching for dark matter through low background detectors and event rejection, I move on to a description of the LUX experiment and its performance, reviewing its internal structure and subsystems including a novel heat exchange system that expedited system readiness and resulted in a stable platform for WIMP searching. The LUX energy reconstruction is then examined, followed by a breakdown of signal fluctuations as a function of energy as part of our understanding of back- ground discrimination in this class of detectors. Finally, I review the first LUX WIMP search result, culminating in the world's most sensitive limit on the spin- independent WIMP-nucleon cross section, before moving to a discussion of next steps in the search for dark matter for LUX and next generational experiments.
Digital Advances in Triggering and Data Acquisition Systems for Large Scale Dark Matter Search Experiments
Author: Eryk Filip DruszkiewiczPublisher:
ISBN:
Category :
Languages : en
Pages : 280
Book Description
"With a wealth of astrophysical evidence that confirms that the baryonic matter we understand accounts for only 5% of the matter and energy in the universe, the search is on for the mysterious dark matter, that is said to account for 25% of the universe composition. The leading candidate for dark matter is the Weakly Interacting Massive Particle (WIMP). Large Underground Xenon (LUX), a 370 kg two-phase (liquid/gas) xenon time projection chamber operating at 4850 feet underground at the Sanford Underground Research Facility (SURF), has recently completed its operation, setting the world's best limit on the WIMP-nucleon cross section. This thesis presents the author's research and development of a novel, FPGA-based, triggering system. This system has operated at SURF since 2011 and through digital signal processing techniques identified events of interest in real-time. The system processes the incoming data at its filter stages with a rate of 5,100 MB/s and does so consuming a total of only 15 W. The firmware and software were entirely developed by the author, while the custom-built hardware was developed in close collaboration with the author. The system offers great flexibility through the reconfigurability feature of FPGAs, which was exercised often during the course of the experiment. The system allows for fully remote operation, minimizing the personnel needs one mile underground. For this type of detectors, this triggering system has shown to offer the highest efficiency in detecting signals as small as few liquid electrons. An FIR digital filter implementation is presented, that has been tailored for this application and offers an up to 99% and 97% savings in scalars and summers utilization, respectively. LUX-Zepplin (LZ) is a next-generation dark matter detector, that is scheduled to start probing the remainder of the uncharted WIMP-nucleon cross section in 2020. It is a significantly larger successor of LUX, with a total xenon mass of 10 tonne. It will be instrumented with 745 photomultipliers, totaling 1,359 digitizing channels. The author is developing the LZ Data Acquisition and Data Sparsification system. This system is going to handle a continuous input rate of over 200 GB/s and its key elements have already been shown to meet and exceed the LZ requirements. Techniques are presented for allowing data volume footprint reduction, such as efficient digitized pulse storage, offering up to 45% reduction in the effective pulse storage size."--Pages xi-xii.