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1. Fluorescence imaging of individual ions and molecules in pressurized noble gases for barium tagging in 136Xe

   https://doi.org/10.1038/s41467-024-54872-0  

   Byrnes, N K; Dey, E; Foss, F W; Jones, B_J P; Madigan, R; McDonald, A D; Miller, R L; Norman, L R; Navarro, K E; Nygren, D R; et al (December 2024, Nature Communications)

   Abstract The imaging of individual Ba²⁺ions in high pressure xenon gas is one possible way to attain background-free sensitivity to neutrinoless double beta decay and hence establish the Majorana nature of the neutrino. In this paper we demonstrate selective single Ba²⁺ion imaging inside a high-pressure xenon gas environment. Ba²⁺ions chelated with molecular chemosensors are resolved at the gas-solid interface using a diffraction-limited imaging system with scan area of 1 × 1 cm²located inside 10 bar of xenon gas. This form of microscopy represents key ingredient in the development of barium tagging for neutrinoless double beta decay searches in¹³⁶Xe. This also provides a new tool for studying the photophysics of fluorescent molecules and chemosensors at the solid-gas interface to enable bottom-up design of catalysts and sensors. 

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2. The EXO-200 detector, part II: auxiliary systems

   https://doi.org/10.1088/1748-0221/17/02/P02015  

   Ackerman, N.; Albert, J.; Auger, M.; Auty, D.J.; Badhrees, I.; Barbeau, P.S.; Bartoszek, L.; Baussan, E.; Belov, V.; Benitez-Medina, C.; et al (February 2022, Journal of Instrumentation)

   Abstract The EXO-200 experiment searched for neutrinoless double-beta decay of 136 Xe with a single-phase liquid xenon detector. It used an active mass of 110 kg of 80.6%-enriched liquid xenon in an ultra-low background time projection chamber with ionization and scintillation detection and readout. This paper describes the design and performance of the various support systems necessary for detector operation, including cryogenics, xenon handling, and controls. Novel features of the system were driven by the need to protect the thin-walled detector chamber containing the liquid xenon, to achieve high chemical purity of the Xe, and to maintain thermal uniformity across the detector. 

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3. A next-generation liquid xenon observatory for dark matter and neutrino physics

   https://doi.org/10.1088/1361-6471/ac841a  

   Aalbers, J.; AbdusSalam, S. S.; Abe, K.; Aerne, V.; Agostini, F.; Ahmed Maouloud, S.; Akerib, D. S.; Akimov, D. Y.; Akshat, J.; Al Musalhi, A. K.; et al (December 2022, Journal of Physics G: Nuclear and Particle Physics)

   Abstract The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector. 

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4. Performance of a large area photon detector for rare event search applications

   https://doi.org/10.1063/5.0032372  

   Fink, C_W; Watkins, S_L; Aramaki, T.; Brink, P_L; Camilleri, J.; Defay, X.; Ganjam, S.; Kolomensky, Yu_G; Mahapatra, R.; Mirabolfathi, N.; et al (January 2021, Applied Physics Letters)

   We present the design and characterization of a large-area Cryogenic PhotoDetector designed for active particle identification in rare event searches, such as neutrinoless double beta decay and dark matter experiments. The detector consists of a 45.6 cm2 surface area by a 1-mm-thick 10.6 g Si wafer. It is instrumented with a distributed network of Quasiparticle-trap-assisted Electrothermal feedback Transition-edge sensors with superconducting critical temperature Tc=41.5 mK to measure athermal phonons released from interactions with photons. The detector is characterized and calibrated with a collimated 55Fe x-ray source incident on the center of the detector. The noise equivalent power is measured to be 1×10−17 W/Hz in a bandwidth of 2.7 kHz. The baseline energy resolution is measured to be σE=3.86±0.04 (stat.)−0.00+0.19 (syst.) eV. The detector also has an expected timing resolution of σt=2.3 μs for 5 σE events. 

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5. Surface Characterization of P-Type Point Contact Germanium Detectors

   https://doi.org/10.3390/particles4040036  

   Edzards, Frank; Hauertmann, Lukas; Abt, Iris; Gooch, Chris; Lehnert, Björn; Liu, Xiang; Mertens, Susanne; Radford, David C.; Schulz, Oliver; Willers, Michael (December 2021, Particles)

   P-type point contact (PPC) germanium detectors are used in rare event and low-background searches, including neutrinoless double beta (0νββ) decay, low-energy nuclear recoils, and coherent elastic neutrino-nucleus scattering. The detectors feature an excellent energy resolution, low detection thresholds down to the sub-keV range, and enhanced background rejection capabilities. However, due to their large passivated surface, separating the signal readout contact from the bias voltage electrode, PPC detectors are susceptible to surface effects such as charge build-up. A profound understanding of their response to surface events is essential. In this work, the response of a PPC detector to alpha and beta particles hitting the passivated surface was investigated in a multi-purpose scanning test stand. It is shown that the passivated surface can accumulate charges resulting in a radial-dependent degradation of the observed event energy. In addition, it is demonstrated that the pulse shapes of surface alpha events show characteristic features which can be used to discriminate against these events. 

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