arXiv subjects

Tommaso Comellato

Publications and source records attributed to Tommaso Comellato.

5 recordsLinked to original sources

arXiv2025

First operation of poly(ethylene naphthalate) enclosures for high-purity germanium detectors in liquid argon for $^{42}$K/$^{42}$Ar mitigation

Commercial argon contains cosmogenic $^{42}$Ar whose progeny $^{42}$K is a critical background component for the Large Enriched Germanium Experiment for Neutrinoless $ββ$ Decay (LEGEND). LEGEND operates High-Purity Germanium (HPGe) detectors bare in liquid argon. $^{42}$K is attracted by the HPGe detectors' electric fields, and drifts toward the germanium surface, where it undergoes beta decay. LEGEND-1000 will mitigate $^{42}$K-induced background by using underground-sourced argon, depleted in cosmogenic isotopes. If underground argon is not available, mitigation techniques must be employed. Poly(ethylene naphthalate) (PEN) enclosures were proposed to hinder the ion drift, decrease the beta-particle's energy, and produce scintillation light. In this paper, we report on operating two HPGe detectors, both bare and PEN-enclosed, in $^{42}$Ar-enriched liquid argon, and find no evidence for deterioration of energy stability or resolution due to the enclosures. We monitor the beta and gamma rates of $^{42}$K, find complex time-dependencies extending to roughly 30 days after applying the HPGe detectors' high-voltage, and qualitatively demonstrate the $^{42}$K suppression capabilities of enclosures.

physics.ins-det↗

arXiv2025

$^{42}$Ar Production and Injection to a Liquid Argon Environment for Background Mitigation Studies

Atmosphere-sourced argon contains traces of $^{42}$Ar, whose $β^-$-decaying progeny $^{42}$K represents a significant intrinsic background for rare-event experiments using liquid argon (LAr) as detector or shielding medium. Understanding and mitigating this background is crucial for current and future large-scale detectors in neutrino and dark-matter physics. To enable controlled studies of $^{42}$K behavior and suppression techniques, $^{42}$Ar was produced by irradiating natural argon with 34 MeV $^{7}$Li$^{3+}$ ions at the Maier-Leibnitz-Laboratorium tandem accelerator, using beam currents of $101 \pm 5$ nA and $140 \pm 5$ nA, yielding $476 \pm 9$ Bq within two weeks, corresponding to a production rate of $\sim 1 \times 10^{6}$ atoms$\,$s$^{-1}$. The activated argon was injected into the one-ton SCARF cryostat, where two HPGe detectors monitored the subsequent $^{42}$K activity build-up. A time-dependent model describing $^{42}$Ar mixing and $^{42}$K equilibration in LAr yielded characteristic mixing time constants between one and two days. The established production and injection capability provides a reproducible platform for high-statistics $^{42}$K background studies, essential for developing and validating suppression strategies for next-generation LAr-based rare-event experiments such as LEGEND-1000.

physics.ins-det↗

arXiv2023

Topologies of $^{76}$Ge double-beta decay events and calibration procedure biases

The analysis of the time profile of electrical signals produced by energy depositions in germanium detectors allows discrimination of events with different topologies. This is especially relevant for experiments searching for the neutrinoless double beta decay of $^{76}$Ge to distinguish the sought-after signal from other background sources. The standard calibration procedures used to tune the selection criteria for double-beta decay events use a $^{228}$Th source, because it provides samples of signal-like events. These samples exhibit energy spatial distributions with subtle different topologies compared to neutrinoless double-beta decay events. In this work, we will characterize these topological differences and, with the support of a $^{56}$Co source, evaluate biases and precision of calibration techniques which use such event samples. Our results will be particularly relevant for future experiments in which a solid estimation of the efficiency is required.

hep-ex↗

arXiv2021

Charge-carrier collective motion in germanium detectors for ββ-decay searches

The time analysis of the signal induced by the drift of charge carriers in high purity germanium detectors provides information on the event topology. Millions of charge carriers are produced in a typical event. Their initial distribution, stochastic diffusion and Coulomb self-repulsion affect the time structure of the signal. We present a comprehensive study of these effects and evaluate their impact on the event discrimination capabilities for the three geometries which will be used in the Legend experiment for neutrinoless double-beta decay.

physics.ins-det↗

arXiv2019

Modeling of GERDA Phase II data

The GERmanium Detector Array (GERDA) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double-beta ($0νββ$) decay of $^{76}$Ge. The technological challenge of GERDA is to operate in a "background-free" regime in the region of interest (ROI) after analysis cuts for the full 100$\,$kg$\cdot$yr target exposure of the experiment. A careful modeling and decomposition of the full-range energy spectrum is essential to predict the shape and composition of events in the ROI around $Q_{ββ}$ for the $0νββ$ search, to extract a precise measurement of the half-life of the double-beta decay mode with neutrinos ($2νββ$) and in order to identify the location of residual impurities. The latter will permit future experiments to build strategies in order to further lower the background and achieve even better sensitivities. In this article the background decomposition prior to analysis cuts is presented for GERDA Phase II. The background model fit yields a flat spectrum in the ROI with a background index (BI) of $16.04^{+0.78}_{-0.85} \cdot 10^{-3}\,$cts/(kg$\cdot$keV$\cdot$yr) for the enriched BEGe data set and $14.68^{+0.47}_{-0.52} \cdot 10^{-3}\,$cts/(kg$\cdot$keV$\cdot$yr) for the enriched coaxial data set. These values are similar to the one of Gerda Phase I despite a much larger number of detectors and hence radioactive hardware components.

nucl-ex↗