Liquid-phase Purification for Multi-ton Xenon Detectors and a Search for Dark Matter and Neutrinos in XENON1T PDF Download

Author: Joseph Howlett
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
This thesis describes research I conducted within the XENON program of dark matter searches. In particular, I focus on contributions I made to the development of a novel system for purifying liquid xenon employed in XENONnT, to the reconstruction and modeling of electronic and nuclear recoil signals by fitting calibration data, and in the employment of these tools to world-leading physics searches for spin-dependent DM-nucleus scattering and coherent neutrino-nucleus scattering from boron-8 solar neutrinos.

Author: Brian Gregory Lenardo
Publisher:
ISBN: 9780438289567
Category :
Languages : en
Pages :

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This dissertation focuses on the characterization of xenon as a detection medium for low energy particle physics. In particular, there are two signals that we are interested in exploring: the interactions of WIMP dark matter inside an earth-bound detector, and the coherent elastic scattering of neutrinos off of nuclei. Both are predicted to produce low energy (10−1--102 keV) nuclear recoils, which can be measured in a low-threshold detector. One well-established technique for measuring these signals is the dual-phase xenon emission detector, which measures primary scintillation light and electroluminescence from ionized electrons to reconstruct information about each interaction inside the target volume. To understand the data produced in an experiment, one must understand how the scintillation and ionization signals relate to the incident particle type and energy deposited. Calibrating the response of the detector medium is of crucial importance for both interpreting existing data and calculating the physics reach of current or future experiments. The ultimate goal of this dissertation is to provide a set of robust models of xenon ionization and scintillation emission which can can be used to calculate signals and simulate the response of liquid xenon detectors in experiments searching for low energy nuclear recoil signatures. In the work below, I begin with a detailed description of the physics of interest. Chapter 2 introduces the dual-phase xenon TPC and discuss its benefits for these types of experiments. In Chapter 3, we draw upon previous literature to develop a model of xenon scintillation and ionization yields. This model is fitted simultaneously to a compilation of available data to allow it to incorporate differences in operating conditions, such as applied electric field, across different experiments. Chapter 4 extends this modeling effort to work within the LUX collaboration, which operated a 300 kg liquid xenon TPC with world-leading sensitivity to dark matter WIMP interactions. LUX performed the lowest-energy nuclear recoil calibration measurements to date, allowing us to extend our model to lower energies and establishing the sensitivity of LUX to a broader range of WIMP models. Chapter 5 delves in greater detail into the time structure of scintillation in liquid xenon. We provide new data on scintillation pulse shapes for low energy nuclear recoils, and use the differences between electron- and nuclear-recoil pulse shapes to establish a new background discriminant for use in LUX data analysis. Finally, in Chapter 6 we describe an ongoing project at LLNL to provide new data of ionization yields at lower energies than the LUX measurements. These experiments will have direct implications on the sensitivity of liquid xenon detectors in general to both low-mass WIMPs and nuclear reactor neutrino scattering. Here we describe the development of the xenon detector system and the preliminary characterization and calibration work that was performed in preparation for the main experiments.

Author: Christopher Pete Benson
Publisher:
ISBN:
Category :
Languages : en
Pages : 192

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Many compelling pieces of indirect evidence pointing to the existence of dark matter. While a confirmed and direct signature of dark matter has yet to be observed, many theoretical models have been developed in an attempt to explain the indirect evidence and to provide phenomenological models that can be tested with targeted experiments. The WIMP is a well-motivated dark matter candidate currently being sought for by several experiments. A variety of detector technologies are utilized, including liquid noble detectors, to look for WIMP scattering as a direct signature of dark matter. The CLEAN experiment is a proposed single-phase, monolithic, large-scale liquid argon experiment designed to look for high-mass WIMPs. A liquid neon target could be exchanged with the argon target to study solar neutrinos and to test the A2 dependence of a possible dark matter signal. Before scaling up to the multi-tonne scale of the full CLEAN detector, the design philosophy and background rejection capabilities required for the next-generation project are being tested using the MiniCLEAN prototype. As of mid-2018, MiniCLEAN has been constructed at SNOLAB and is currently being filled with natural liquid argon for a dark matter run. Following a short dark matter run, MiniCLEAN will be spiked with elevated levels of 39Ar to test the scaling limits of pulse shape discrimination, the primary method for electronic background rejection. These results will inform existing experiments and the next-generation of large-scale liquid argon detectors. A good understanding of light propagation is critical for optical experiments such as CLEAN, whose event reconstruction and background rejection relies primarily on scintillation light collection. This work presents two classes of complementary results which are expected to improve the modeling of scintillation light collection in current and future neutrino and dark matter detectors. These are, first, the dependence of the scintillation light time structure (triplet lifetime) and relative light yield of gaseous argon as a function of impurity level and, second, the measurement of several parameters critical to constructing a microphysically-motivated model of tetraphenyl butadiene (TPB) wavelength shifting thin films - a technology which is commonly used in many existing and proposed liquid noble gas experiments.

Author: Daniel Wenz
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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A rich number of astronomical and cosmological observations suggest the existence of a massive, non-luminous, and non-relativistic, matter component in the universe which is five times more abundant than baryonic matter and is commonly referred as to dark matter (DM). Although so far eluding from detection, one class of promising DM candidates are weakly interacting massive particles (WIMPs) which arise naturally from many beyond the Standard Model (BSM) theories. The XENON Dark Matter Project aims to directly detect WIMPs, and other kinds of rare event signals, by utilizing large-scale liquid xenon (LXe) dual-phase time projection chambers (TPCs). The newest generation of experiment, called XENONnT, utilizes a TPC with a total sensitive LXe mass of 5.9 t, and was designed as a fast upgrade of its predecessor XENON1T. In addition to its larger TPC, XENONnT was augmented with the world's first water Cherenkov neutron veto (NV), which was mounted inside the already existing water Cherenkov muon veto water tank of XENON1T. Neutrons emitted by detector materials can undergo a single back-scatter inside the TPC producing a signal which is indistinguishable from WIMPs. The NV has the task to mitigate this potential threat for the scientific reach of the experiment by tagging these escaping neutrons through their delayed neutron capture on hydrogen. In the presented work, the results of the first weakly interacting massive particle (WIMP) search science run, called SR0, are discussed. SR0 features a blind analysis between 3.3 keV and 60.5 keV nuclear recoils energies with a total exposure of about 1.1 tonne-year, utilizing the lowest ever achieved electronic recoil background of (15.8 ± 1.3) events/(t · y · keV) in a LXe. No significant excess was found in the data, setting the lowest upper limit of 2.58 · 10-47 cm2 for spin-independent (SI) interactions of 28 GeV/c2 WIMPs at a 90% confidence level. These results have also been published in [Apr+23b] as part of the presented work. To obtain these results, this thesis discusses the commissioning of the XENONnT neutron veto (NV), and the calibration of its neutron tagging efficiency. The tagging efficiency was found to be (53.1±2.8)% which is the highest efficiency ever measured in a water Cherenkov detector. The efficiency of the NV, as well as the nuclear recoil (NR) response of the time projection chamber (TPC), were calibrated using tagged neutrons from an Americium-Beryllium (AmBe) neutron source. This technique was deployed for the first time in a liquid xenon (LXe) TPC. It enables a calibration of the NR response with high purity and a remaining pollution of less than 0.1 %. Further, the same calibration data was used to determine the thermal neutron capture cross section of hydrogen which was found to be 336.7 ± 0.4 (stat.)+2.0 -0.0 (sys.) mb. All these analyses are based on the data provided by XENONnT's new processing framework called STRAXEN. As part of the lead developing team, the entire processing chain for the two veto systems of XENONnT was developed, and many additional tools have been implemented. Finally, to enhance the neutron tagging efficiency of the NV even further, the water inside the water tank is going to be doped with Gd-sulfate. As part of the presented work, different Gd-salt samples of the manufacturer Treibacher were analyzed regarding their suitability for the experiment.

Author: Elena Aprile
Publisher: John Wiley & Sons
ISBN: 3527609636
Category : Science
Languages : en
Pages : 362

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Book Description
This book discusses the physical properties of noble fluids, operational principles of detectors based on these media, and the best technical solutions to the design of these detectors. Essential attention is given to detector technology: purification methods and monitoring of purity, information readout methods, electronics, detection of hard ultra-violet light emission, selection of materials, cryogenics etc. The book is mostly addressed to physicists and graduate students involved in the preparation of fundamental next generation experiments, nuclear engineers developing instrumentation for national nuclear security and for monitoring nuclear materials.

Author:
Publisher:
ISBN:
Category : Breakdown (Electricity)
Languages : en
Pages : 484

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Author: Chiara Capelli
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: E. Bellotti
Publisher: IOS Press
ISBN: 1614990085
Category : Science
Languages : en
Pages : 321

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Neutrino physics contributed in an fundamental way to the progress of science, opening important windows of knowledge in elementary particle physics, as well in astrophysics and cosmology. Substantial experimental efforts are presently dedicated to improve our knowledge on neutrino properties as, in fact, we don't know yet some of the basic ones. Although very significant steps forward have been done, neutrino masses and mixings still remain largely unknown and constitute an important field for future research. Are neutrinos Majorana or Dirac particles? Have they a magnetic moment? Historically, studies on weak processes and, therefore, on neutrino physics, provided first the Fermi theory of weak interactions and then the V-A theory. Finally, the observation of weak neutral currents provided the first experimental evidence for unification of weak and electromagnetic interactions by the so called "Standard Model' of elementary particles. In addition to the results obtained from the measurement of the solar neutrino flux, the study of atmospheric neutrinos strongly supports the hypothesis of neutrino oscillation among different flavours. At the same time, the detection of neutrinos emitted by our Sun gave an important confirmation that the Sun produces energy via a chain of nuclear reactions; in particular in our Sun a specific cycle - the hydrogen cycle - is responsible for practically all the produced energy.

Author: Aaron Mitchell Cossey
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 79

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A simplified two-dimensional finite volume axisymmetric mesh was constructed that represented the geometry of the Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) experiment in order to perform a computational fluid dynamics (CFD) analysis of the purification process of the liquid scintillator (LS). 1,000 tons of the LS, contained within a 13 meter-diameter spherical balloon in the center of the detector, is purified in a continuous process where the LS is simultaneously withdrawn from the bottom and replaced at the top of the detector. During this purification process, the interface between the newly purified and unpurified LS is not stratified horizontally as expected, but instead mixing is observed, reducing the efficiency of the process and preventing the desired level of purification throughout the LS. Using the commercial CFD software FLUENT, the purification process of the experiment was simulated based on the conditions and data previously recorded during the purification phase. The CFD analysis of the experiment was modeled as a transient problem, with flow and heat transfer solved. The phenomenon of natural convection was modeled using the Boussinesq approximation. The volume of fraction (VOF) method was used to track the interaction between the purified and unpurified liquids in the simulation. The CFD simulation will be used to test proposed improvements to the purification process for future purification programs of KamLAND. The CFD simulation will serve as a guide to test these improvements and improve the efficiency of the process.

Author: Yi-Hsuan Lin
Publisher:
ISBN:
Category : Double beta decay
Languages : en
Pages : 121

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An observation of neutrinoless double beta decay, a hypothetical second-order weak interaction, may reveal the Dirac/Majorana nature of the neutrinos and demonstrate lepton number violation. The EXO-200 experiment was designed to search for neutrinoless double beta decay using an ultra-low background single-phase time projection chamber. The detector contains 110~kg of active liquid xenon, isotopically enriched in Xe-136, which acts as both the decaying nucleus and detection medium. To optimize the signal of such a detector, the liquid xenon needs to be kept free of electronegative impurities which could interact with drifting electron signals and reduce energy resolution. This study investigates whether fitting the ionization signals from the two time projection chamber halves separately or combining the datasets for fitting yields a more accurate purity correction. The latter method was found to improve the purity correction on the EXO-200 data and has been implemented in the EXO-200 standard analysis pipeline. Using the combined dataset, a purification model and its modifications have been developed and tested. The purification model utilizes the physical parameters measured in the detector and can improve the understanding of purity behavior in the detector, while providing detector measurements. The fitting performance of the 2-Phase Model to EXO-200 electron lifetime data is shown to be comparable to that of the polynomial function method. In addition, the 2-Phase Model can adapt to changes in the system and does not require human input, thus eliminating any inconsistency in the purity correction for the ionization energy in the physics data.