Design Challenges for a Future Liquid Xenon Observatory

An ultimate liquid xenon experiment would be limited in its dark matter science reach by irreducible neutrino backgrounds, which are an exciting signal in their own right. To achieve such sensitivity, other backgrounds that currently plague these detectors must be better mitigated, and extreme care must be taken in the design and construction phases. A 100-tonne xenon target is compelling to search for weakly interacting massive particle dark matter, and has capabilities to study coherent elastic neutrino-nucleus scattering and search for neutrinoless double-beta decay signatures. Historically, liquid xenon time projection chambers have scaled to larger target masses with great success. This paper gives an overview of challenges that need to be met for the next generation of detector to obtain a kilotonne×year exposure. Such tasks include the procurement and purification of xenon, radiopure and reliable detector components, sensitive outer detector vetoes, powerful data handling and analyses, and an ability to operate stably for timescales of over a decade

Low Energy Electronic Recoils and Single Electron Detection with a Liquid Xenon Proportional Scintillation Counter

Liquid xenon (LXe) is a well-studied detector medium to search for rare events in dark matter and neutrino physics. Two-phase xenon time projection chambers (TPCs) can detect electronic and nuclear recoils with energy down to kilo-electron volts (keV). In this paper, we characterize the response of a single-phase liquid xenon proportional scintillation counter (LXePSC), which produces electroluminescence directly in the liquid, to detect electronic recoils at low energies. Our design uses a thin (10 - 25 $\mu$m diameter), central anode wire in a cylindrical LXe target where ionization electrons, created from radiation particles, drift radially towards the anode, and electroluminescence is produced. Both the primary scintillation (S1) and electroluminescence (S2) are detected by photomultiplier tubes (PMTs) surrounding the LXe target. Up to 17 photons are produced per electron, obtained with a 10 $\mu$m diameter anode wire, allowing for the highly efficient detection of electronic recoils from beta decays of a tritium source down to roughly 1 keV. Single electrons, from photo-emission of the cathode wires, are observed at a gain of 1.8 photoelectrons (PE) per electron. The delayed signals following the S2 signals are dominated by single-photon-like hits, without evidence for electron signals observed in the two-phase xenon TPCs. We discuss the potential application of such a LXePSC for reactor neutrino detection via Coherent Elastic Neutrino Nucleus Scattering (CE$\nu$NS).Comment: 18 pages, 17 figure

Few-Electron Signals in Liquid Xenon Dark Matter Detectors

An overwhelming majority of matter in the Universe is dark matter, a substance unlike anything we know. Detecting dark matter particles requires ruling out observed phenomena caused by known particles. This thesis advances efforts toward the detection of dark matter using one of the most sensitive particle detection technologies: the dual-phase liquid xenon time projection chamber. Specifically, data from the XENON1T Experiment, located in Italy, and the Purdue small-scale ASTERiX detector are analyzed. A background of Lead214 beta decay events can be mitigated by tracing the radioactive Radon-222 decay chain in XENON1T. However, a preliminary reduction of background has a high cost to exposure. Research on several topics was conducted with Purdue undergraduates, including a search for dark matter particles up to the Planck Mass, characterizing backgrounds due to muons, and searching for Boron-8 solar neutrino signals. XENON1T single-scatter dark matter limits were extended to a particle mass of 1018 GeV/c2. The ASTERiX detector was modified to characterize a significant background to the smallest detectable energy signatures: singleand few-electron ionization signals. Infrared light was determined to be ineffective at reducing this background, and their rates were observed to decrease inversely with time since an energetic interaction according to a power law. The rates of single- and few- electron backgrounds increase linearly with increased applied extraction fields and increased depth of the initial interaction in the detector. These results indicate that these backgrounds originate at the liquid-gas interface of dual-phase detectors. In exploring a single-photon threshold for initial scintillation signals, a previously unconsidered background of large dark count signals in the photosensors became apparent. The high background of small ionization signals and large dark count signals deterred a search for Boron-8 solar neutrino interactions in XENON1T. These studies are vital to mitigating backgrounds and improving the sensitivity of liquid xenon time projection chambers to new physical phenomena

Sex differences in the effects of high fat diet on underlying neuropathology in a mouse model of VCID

Abstract Background Damage to the cerebral vasculature can lead to vascular contributions to cognitive impairment and dementia (VCID). A reduction in blood flow to the brain leads to neuropathology, including neuroinflammation and white matter lesions that are a hallmark of VCID. Mid-life metabolic disease (obesity, prediabetes, or diabetes) is a risk factor for VCID which may be sex-dependent (female bias). Methods We compared the effects of mid-life metabolic disease between males and females in a chronic cerebral hypoperfusion mouse model of VCID. C57BL/6J mice were fed a control or high fat (HF) diet starting at ~ 8.5 months of age. Three months after diet initiation, sham or unilateral carotid artery occlusion surgery (VCID model) was performed. Three months later, mice underwent behavior testing and brains were collected to assess pathology. Results We have previously shown that in this VCID model, HF diet causes greater metabolic impairment and a wider array of cognitive deficits in females compared to males. Here, we report on sex differences in the underlying neuropathology, specifically white matter changes and neuroinflammation in several areas of the brain. White matter was negatively impacted by VCID in males and HF diet in females, with greater metabolic impairment correlating with less myelin markers in females only. High fat diet led to an increase in microglia activation in males but not in females. Further, HF diet led to a decrease in proinflammatory cytokines and pro-resolving mediator mRNA expression in females but not males. Conclusions The current study adds to our understanding of sex differences in underlying neuropathology of VCID in the presence of a common risk factor (obesity/prediabetes). This information is crucial for the development of effective, sex-specific therapeutic interventions for VCID

Collaborative experience between scientific software projects using Agile Scrum development

Developing sustainable software for the scientific community requires expertise in software engineering and domain science. This can be challenging due to the unique needs of scientific software, the insufficient resources for software engineering practices in the scientific community, and the complexity of developing for evolving scientific contexts. While open-source software can partially address these concerns, it can introduce complicating dependencies and delay development. These issues can be reduced if scientists and software developers collaborate. We present a case study wherein scientists from the SuperNova Early Warning System collaborated with software developers from the Scalable Cyberinfrastructure for Multi-Messenger Astrophysics project. The collaboration addressed the difficulties of open-source software development, but presented additional risks to each team. For the scientists, there was a concern of relying on external systems and lacking control in the development process. For the developers, there was a risk in supporting a user-group while maintaining core development. These issues were mitigated by creating a second Agile Scrum framework in parallel with the developers' ongoing Agile Scrum process. This Agile collaboration promoted communication, ensured that the scientists had an active role in development, and allowed the developers to evaluate and implement the scientists' software requirements. The collaboration provided benefits for each group: the scientists actuated their development by using an existing platform, and the developers utilized the scientists' use-case to improve their systems. This case study suggests that scientists and software developers can avoid scientific computing issues by collaborating and that Agile Scrum methods can address emergent concerns

Inhibition of Calcineurin-mediated Endocytosis and α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptors Prevents Amyloid β Oligomer-induced Synaptic Disruption

Synaptic degeneration, including impairment of synaptic plasticity and loss of synapses, is an important feature of Alzheimer disease pathogenesis. Increasing evidence suggests that these degenerative synaptic changes are associated with an accumulation of soluble oligomeric assemblies of amyloid β (Aβ) known as ADDLs. In primary hippocampal cultures ADDLs bind to a subpopulation of neurons. However the molecular basis of this cell type-selective interaction is not understood. Here, using siRNA screening technology, we identified α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits and calcineurin as candidate genes potentially involved in ADDL-neuron interactions. Immunocolocalization experiments confirmed that ADDL binding occurs in dendritic spines that express surface AMPA receptors, particularly the calcium-impermeable type II AMPA receptor subunit (GluR2). Pharmacological removal of the surface AMPA receptors or inhibition of AMPA receptors with antagonists reduces ADDL binding. Furthermore, using co-immunoprecipitation and photoreactive amino acid cross-linking, we found that ADDLs interact preferentially with GluR2-containing complexes. We demonstrate that calcineurin mediates an endocytotic process that is responsible for the rapid internalization of bound ADDLs along with surface AMPA receptor subunits, which then both colocalize with cpg2, a molecule localized specifically at the postsynaptic endocytic zone of excitatory synapses that plays an important role in activity-dependent glutamate receptor endocytosis. Both AMPA receptor and calcineurin inhibitors prevent oligomer-induced surface AMPAR and spine loss. These results support a model of disease pathogenesis in which Aβ oligomers interact selectively with neurotransmission pathways at excitatory synapses, resulting in synaptic loss via facilitated endocytosis. Validation of this model in human disease would identify therapeutic targets for Alzheimer disease