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1. Low-energy calibration of XENON1T with an internal $$^{{\textbf {37}}}$$Ar source

   https://doi.org/10.1140/epjc/s10052-023-11512-z  

   Aprile, E.; Abe, K.; Agostini, F.; Ahmed Maouloud, S.; Alfonsi, M.; Althueser, L.; Andrieu, B.; Angelino, E.; Angevaare, J. R.; Antochi, V. C.; et al (June 2023, The European Physical Journal C)

   Abstract A low-energy electronic recoil calibration of XENON1T, a dual-phase xenon time projection chamber, with an internal $${}^{37}$$ 37 Ar source was performed. This calibration source features a 35-day half-life and provides two mono-energetic lines at 2.82 keV and 0.27 keV. The photon yield and electron yield at 2.82 keV are measured to be ( $$32.3\,\pm \,0.3$$ 32.3 ± 0.3 ) photons/keV and ( $$40.6\,\pm \,0.5$$ 40.6 ± 0.5 ) electrons/keV, respectively, in agreement with other measurements and with NEST predictions. The electron yield at 0.27 keV is also measured and it is ( $$68.0^{+6.3}_{-3.7}$$ 68 . 0 - 3.7 + 6.3 ) electrons/keV. The $${}^{37}$$ 37 Ar calibration confirms that the detector is well-understood in the energy region close to the detection threshold, with the 2.82 keV line reconstructed at ( $$2.83\,\pm \,0.02$$ 2.83 ± 0.02 ) keV, which further validates the model used to interpret the low-energy electronic recoil excess previously reported by XENON1T. The ability to efficiently remove argon with cryogenic distillation after the calibration proves that $${}^{37}$$ 37 Ar can be considered as a regular calibration source for multi-tonne xenon detectors. 

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2. Development of a ¹²⁷ Xe calibration source for nEXO

   https://doi.org/10.1088/1748-0221/17/07/P07028  

   Lenardo, B.G.; Hardy, C.A.; Tsang, R.H.M.; Nzobadila Ondze, J.C.; Piepke, A.; Triambak, S.; Jamil, A.; Adhikari, G.; Al Kharusi, S.; Angelico, E.; et al (July 2022, Journal of Instrumentation)

   Abstract We study a possible calibration technique for the nEXO experiment using a 127 Xe electron capture source. nEXO is a next-generation search for neutrinoless double beta decay (0 νββ ) that will use a 5-tonne, monolithic liquid xenon time projection chamber (TPC). The xenon, used both as source and detection medium, will be enriched to 90% in 136 Xe. To optimize the event reconstruction and energy resolution, calibrations are needed to map the position- and time-dependent detector response. The 36.3 day half-life of 127 Xe and its small Q-value compared to that of 136 Xe 0 νββ would allow a small activity to be maintained continuously in the detector during normal operations without introducing additional backgrounds, thereby enabling in-situ calibration and monitoring of the detector response. In this work we describe a process for producing the source and preliminary experimental tests. We then use simulations to project the precision with which such a source could calibrate spatial corrections to the light and charge response of the nEXO TPC. 

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3. Quasi‐Trapped Electron Fluxes Induced by NWC Transmitter and CRAND: Observations and Simulations

   https://doi.org/10.1029/2021GL097443  

   Liu, Yangxizi; Xiang, Zheng; Ni, Binbin; Li, Xinlin; Zhang, Kun; Fu, Song; Gu, Xudong; Liu, Jiang; Cao, Xing (March 2022, Geophysical Research Letters)

   Abstract Signals from the NWC ground‐based very low frequency (VLF) transmitter can leak into the magnetosphere and scatter trapped energetic electrons into drift loss cones. Recent studies also suggest that cosmic ray albedo neutron decay (CRAND) is probably an important source for quasi‐trapped electrons in the inner belt. To investigate their relative contributions, this study comprehensively analyzes the long‐term variations of quasi‐trapped 206 keV electrons atL = 1.7, which is roughly the L shell where NWC is located. Furthermore, a drift‐diffusion‐source model is used to reproduce longitudinal distributions of quasi‐trapped electrons and investigate sensitivities of simulation results to VLF transmitter intensities. These results suggest that CRAND is the main source of quasi‐trapped hundreds of keV electrons when the NWC station is at dayside. In contrast, pitch angle diffusions become the main source mechanism of these quasi‐trapped electrons when the NWC station operates at nightside with more VLF transmitter energy leaking into the magnetosphere. 

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4. Demonstration of event position reconstruction based on diffusion in the NEXT-white detector

   https://doi.org/10.1140/epjc/s10052-024-12865-9  

   Haefner, J; Navarro, K E; Guenette, R; Jones, B_J P; Tripathi, A; Adams, C; Almazán, H; Álvarez, V; Aparicio, B; Aranburu, A I; et al (May 2024, The European Physical Journal C)

   Noble element time projection chambers are a leading technology for rare event detection in physics, such as for dark matter and neutrinoless double beta decay searches. Time projection chambers typically assign event position in the drift direction using the relative timing of prompt scintillation and delayed charge collection signals, allowing for reconstruction of an absolute position in the drift direction. In this paper, alternate methods for assigning event drift distance via quantification of electron diffusion in a pure high pressure xenon gas time projection chamber are explored. Data from the NEXT-White detector demonstrate the ability to achieve good position assignment accuracy for both high- and low-energy events. Using point-like energy deposits from$$^{83\textrm{m}}$$ ${}^{83\text{m}}$Kr calibration electron captures ($$E\sim 45$$ $E\sim 45$ keV), the position of origin of low-energy events is determined to 2 cm precision with bias$$< 1~$$ $<1$mm. A convolutional neural network approach is then used to quantify diffusion for longer tracks ($$E\ge ~1.5$$ $E\ge 1.5$ MeV), from radiogenic electrons, yielding a precision of 3 cm on the event barycenter. The precision achieved with these methods indicates the feasibility energy calibrations of better than 1% FWHM at Q$$_{\beta \beta }$$ ${}_{\beta \beta }$in pure xenon, as well as the potential for event fiducialization in large future detectors using an alternate method that does not rely on primary scintillation. 

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5. Shades: ²² Ne( α , n) ²⁵ Mg reaction rate in the Gamow window

   https://doi.org/10.1051/epjconf/202226011031  

   Rapagnani, David; Ananna, Chemseddine; Di Leva, Antonino; Imbriani, Gianluca; Junker, Matthias; Pignatari, Marco; Best, Andreas (January 2022, EPJ Web of Conferences)

   Liu, W.; Wang, Y.; Guo, B.; Tang, X.; Zeng, S. (Ed.)

   Neutron capture reactions are the main contributors to the synthesis of the heavy elements through the s-process. Together with 13 C( α , n) 16 O, which has recently been measured by the LUNA collaboration in an energy region inside the Gamow peak, 22 Ne( α , n) 25 Mg is the other main neutron source in stars. Its cross section is mostly unknown in the relevant stellar energy (450 keV < E cm < 750 keV), where only upper limits from direct experiments and highly uncertain estimates from indirect sources exist. The ERC project SHADES (UniNa/INFN) aims to provide for the first time direct cross section data in this region and to reduce the uncertainties of higher energy resonance parameters. High sensitivity measurements will be performed with the new LUNA-MV accelerator at the INFN-LNGS laboratory in Italy: the energy sensitivity of the SHADES hybrid neutron detector, together with the low background environment of the LNGS and the high beam current of the new accelerator promises to improve the sensitivity by over 2 orders of magnitude over the state of the art, allowing to finally probe the unexplored low-energy cross section. Here we present an overview of the project and first results on the setup characterization. 

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