arXiv subjects

K. Schaeffner

Publications and source records attributed to K. Schaeffner.

At least 19 recordsLinked to original sources

arXiv2026

Optimization studies of silicon remoTES cryogenic calorimeters

The remoTES design, developed within the COSINUS experiment, enables a broader range of materials to be operated as cryogenic calorimeters read out with Transition Edge Sensors (TESs). In this configuration, the TES is fabricated onto a separate chip and thermally coupled to the absorber via a gold (Au) link. The remoTES concept has been successfully tested on various target materials. To further enhance detector performance and to fully exploit the advantages of the remote coupling design a series of optimization studies has been conducted using silicon (Si) absorbers as benchmark. This work presents an evaluation of several measurements aimed at reducing the thermal boundary resistance and enhancing signal transmission across Si remoTES interfaces, specifically from the absorber to the phonon collector and from the phonon collector to the TES. By testing a new Au link design and three distinct phonon collector configurations, Au, copper, and aluminum (Al)/Au, we achieved a baseline resolution of (21.5 +/- 0.3)eV using the Al/Au phonon collector.

physics.ins-det↗

arXiv2025

The CRESST experiment: towards the next-generation of sub-GeV direct dark matter detection

Direct detection experiments have established the most stringent constraints on potential interactions between particle candidates for relic, thermal dark matter and Standard Model particles. To surpass current exclusion limits a new generation of experiments is being developed. The upcoming upgrade of the CRESST experiment will incorporate $\mathcal{O}$(100) detectors with different masses ranging from $\sim$2g to $\sim$24g, aiming to achieve unprecedented sensitivity to sub-GeV dark matter particles with a focus on spin-independent dark matter-nucleus scattering. This paper presents a comprehensive analysis of the planned upgrade, detailed experimental strategies, anticipated challenges, and projected sensitivities. Approaches to address and mitigate low-energy excess backgrounds $-$ a key limitation in previous and current sub-GeV dark matter searches $-$ are also discussed. In addition, a long-term roadmap for the next decade is outlined, including other potential scientific applications.

astro-ph.CO↗

arXiv2024

Neutrino flux sensitivity to the next galactic core-collapse supernova in COSINUS

While neutrinos are often treated as a background for many dark matter experiments, these particles offer a new avenue for physics: the detection of core-collapse supernovae. Supernovae are extremely energetic, violent and complex events that mark the death of massive stars. During their collapse stars emit a large number of neutrinos in a short burst. These neutrinos carry 99\% of the emitted energy which makes their detection fundamental in understanding supernovae. This paper illustrates how COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches), a sodium iodide (NaI) based dark matter search, will be sensitive to the next galactic core-collapse supernova. The experiment is composed of two separate detectors which will be sensitive to far and nearby supernovae. The inner core of the experiment will consist of NaI crystals operating as scintillating calorimeters, mainly sensitive to the Coherent Elastic Scattering of Neutrinos (CE$\nu$NS) against the Na and I nuclei. The low mass of the cryogenic detectors gives the experiment a sensitivity to close supernovae below 1kpc without pileup. They will see up to hundreds of CE$\nu$NS events from a supernova happening at 200pc. The crystals reside at the center of a cylindrical 230T water tank, instrumented with 30 photomultipliers. This tank acts as a passive and active shield able to detect the Cherenkov radiation induced by impinging charged particles from ambient and cosmogenic radioactivity. A supernova near the Milky Way Center (10kpc) will be easily detected inducing $\sim$60 measurable events, and the water tank will have a 3$\sigma$ sensitivity to supernovae up to 22kpc, seeing $\sim$10 events. This paper shows how, even without dedicated optimization, modern dark matter experiments will also play their part in the multi-messenger effort to detect the next galactic core-collapse supernova.

astro-ph.HE↗

arXiv2023

Detector development for the CRESST experiment

Recently low-mass dark matter direct searches have been hindered by a low energy background, drastically reducing the physics reach of the experiments. In the CRESST-III experiment, this signal is characterised by a significant increase of events below 200 eV. As the origin of this background is still unknown, it became necessary to develop new detector designs to reach a better understanding of the observations. Within the CRESST collaboration, three new different detector layouts have been developed and they are presented in this contribution.

physics.ins-det↗

arXiv2023

Deep-underground dark matter search with a COSINUS detector prototype

Sodium iodide (NaI) based cryogenic scintillating calorimeters using quantum sensors for signal read out have shown promising first results towards a model-independent test of the annually modulating signal detected by the DAMA/LIBRA dark matter experiment. The COSINUS collaboration has previously reported on the first above-ground measurements using a dual channel readout of phonons and light based on transition edge sensors (TESs) that allows for particle discrimination on an event-by-event basis. In this letter, we outline the first underground measurement of a NaI cryogenic calorimeter read out via the novel remoTES scheme. A 3.67 g NaI absorber with an improved silicon light detector design was operated at the Laboratori Nazionali del Gran Sasso, Italy. A significant improvement in the discrimination power of $e^-$/$\gamma$-events to nuclear recoils was observed with a five-fold improvement in the nuclear recoil baseline resolution, achieving $\sigma$ = 441 eV. Furthermore, we present a limit on the spin-independent dark-matter nucleon elastic scattering cross-section achieving a sensitivity of $\mathcal{O}$(pb) with an exposure of only 11.6 g d.

astro-ph.CO↗

arXiv2023

High-Dimensional Bayesian Likelihood Normalisation for CRESST's Background Model

Using CaWO$_4$ crystals as cryogenic calorimeters, the CRESST experiment searches for nuclear recoils caused by the scattering of potential Dark Matter particles. A reliable identification of a potential signal crucially depends on an accurate background model. In this work we introduce an improved normalisation method for CRESST's model of the electromagnetic backgrounds. Spectral templates, based on Geant4 simulations, are normalised via a Bayesian likelihood fit to experimental background data. Contrary to our previous work, no assumption of partial secular equilibrium is required, which results in a more robust and versatile applicability. Furthermore, considering the correlation between all background components allows us to explain 82.7% of the experimental background within [1 keV, 40 keV], an improvement of 18.6% compared to our previous method.

physics.ins-det↗

arXiv2022

Final Result on the Neutrinoless Double Beta Decay of $^{82}$Se with CUPID-0

CUPID-0, an array of Zn$^{82}$Se cryogenic calorimeters, was the first medium-scale demonstrator of the scintillating bolometers technology. The first project phase (March 2017 - December 2018) allowed the most stringent limit on the neutrinoless double beta decay half-life of the isotope of interest, $^{82}$Se, to be set. After a six months long detector upgrade, CUPID-0 began its second and last phase (June 2019 - February 2020). In this letter, we describe the search for neutrinoless double beta decay of $^{82}$Se with a total exposure (phase I + II) of 8.82 kg$\times$yr of isotope. We set a limit on the half-life of $^{82}$Se to the ground state of $^{82}$Kr of T$^{0\nu}_{1/2}$($^{82}$Se)$>$ 4.6$\times \mathrm{10}^{24}$ yr (90\% credible interval), corresponding to an effective Majorana neutrino mass m$_{\beta\beta} <$ (263 -- 545) meV. We also set the most stringent lower limits on the neutrinoless decays of $^{82}$Se to the 0$_1^+$, 2$_1^+$ and 2$_2^+$ excited states of $^{82}$Kr, finding 1.8$\times$10$^{23}$ yr, 3.0$\times$10$^{23}$ yr, 3.2$\times$10$^{23}$ yr (90$\%$ credible interval) respectively.

hep-ex↗

arXiv2021

First measurements of remoTES cryogenic calorimeters: easy-to-fabricate particle detectors for a wide choice of target materials

Low-temperature calorimeters based on a readout via Transition Edge Sensors (TESs) and operated below $100$ mK are well suited for rare event searches with outstanding resolution and low thresholds. We present first experimental results from two detector prototypes using a novel design of the thermometer coupling denoted remoTES, which further extends the applicability of the TES technology by including a wider class of potential absorber materials. In particular, this design facilitates the use of materials whose physical and chemical properties, as e.g. hygroscopicity, low hardness and low melting point, prevent the direct fabrication of the TES onto their surface. This is especially relevant in the context of the COSINUS experiment (Cryogenic Observatory for SIgnals seen in Next-Generation Underground Searches), where sodium iodide (NaI) is used as absorber material. With two remoTES prototype detectors operated in an above-ground R&D facility, we achieve energy resolutions of $\sigma=87.8$ eV for a $2.33$ g silicon absorber and $\sigma = 193.5$ eV for a $2.27$ g $\alpha$-TeO$_{2}$ absorber, respectively. RemoTES calorimeters offer - besides the wider choice of absorber materials - a simpler production process combined with a higher reproducibility for large detector arrays and an enhanced radiopurity standard.

physics.ins-det↗

arXiv2020

Double Beta Decay APPEC Committee Report

This report constitutes the roadmap document prepared by the Double Beta Decay APPEC Committee for the APPEC SAC on the future neutrinoless double beta decay experimental programme in Europe. It reviews the existing, planned and proposed technologies for neutrinoless double beta decay, their discovery potential and technical challenges, making a critical examination of resources and schedules. It also provides a concise discussion of the theoretical issues and of the status and uncertainties on the nuclear matrix element evaluation.

hep-ex↗

arXiv2019

Production and characterization of a PbMoO$_4$ cryogenic detector from archaeological Pb

We operated a PbMoO$_4$ scintillating cryogenic detector of 570 g, produced with archaeological lead. This compound features excellent low temperature characteristics in terms of light yield, 12 keV/MeV for $β/γ$ interactions, and FWHM energy resolution, 11.7 keV at 2.6 MeV. Furthermore, the detector allows for an effective particle identification by means of pulse shape analysis on the heat read-out channel. The implementation of innovative techniques and procedures for the purification of raw materials used for the crystal growth, and the highly-pure archaeological Pb, allowed the production of large volume high quality crystal. The overall characteristics of the detector operated at cryogenic temperatures makes PbMoO$_4$ an excellent compound for neutrino physics applications, especially neutrinoless double-beta studies.

physics.ins-det↗

arXiv2019

Neutrino physics with the PTOLEMY project: active neutrino properties and the light sterile case

The PTOLEMY project aims to develop a scalable design for a Cosmic Neutrino Background (CNB) detector, the first of its kind and the only one conceived that can look directly at the image of the Universe encoded in neutrino background produced in the first second after the Big Bang. The scope of the work for the next three years is to complete the conceptual design of this detector and to validate with direct measurements that the non-neutrino backgrounds are below the expected cosmological signal. In this paper we discuss in details the theoretical aspects of the experiment and its physics goals. In particular, we mainly address three issues. First we discuss the sensitivity of PTOLEMY to the standard neutrino mass scale. We then study the perspectives of the experiment to detect the CNB via neutrino capture on tritium as a function of the neutrino mass scale and the energy resolution of the apparatus. Finally, we consider an extra sterile neutrino with mass in the eV range, coupled to the active states via oscillations, which has been advocated in view of neutrino oscillation anomalies. This extra state would contribute to the tritium decay spectrum, and its properties, mass and mixing angle, could be studied by analyzing the features in the beta decay electron spectrum.

astro-ph.CO↗

arXiv2018

Search of the neutrino-less double beta decay of $^{82}$Se into the excited states of $^{82}$Kr with CUPID-0

The CUPID0 experiment searches for double beta decay using cryogenic calorimeters with double (heat and light) read-out. The detector, consisting of 24 ZnSe crystals 95$\%$ enriched in $^{82}$Se and 2 natural ZnSe crystals, started data-taking in 2017 at Laboratori Nazionali del Gran Sasso. We present the search for the neutrino-less double beta decay of $^{82}$Se into the 0$_1^+$, 2$_1^+$ and 2$_2^+$ excited states of $^{82}$Kr with an exposure of 5.74 kg$\cdot$yr (2.24$\times$10$^{25}$ emitters$\cdot$yr). We found no evidence of the decays and set the most stringent limits on the widths of these processes: $Γ$($^{82}$Se $\rightarrow ^{82}$Kr$_{0_1^+}$)$<$8.55$\times$10$^{-24}$ yr$^{-1}$, $Γ$($^{82}$Se $\rightarrow ^{82}$Kr$_{2_1^+}$)$<6.25 \times10^{-24}$ yr$^{-1}$, $Γ$($^{82}$Se $\rightarrow ^{82}$Kr$_{2_2^+}$)$<$8.25$\times$10$^{-24}$ yr$^{-1}$ (90$\%$ credible interval

nucl-ex↗

arXiv2018

A Design for an Electromagnetic Filter for Precision Energy Measurements at the Tritium Endpoint

We present a detailed description of the electromagnetic filter for the PTOLEMY project to directly detect the Cosmic Neutrino Background (CNB). Starting with an initial estimate for the orbital magnetic moment, the higher-order drift process of ExB is configured to balance the gradient-B drift motion of the electron in such a way as to guide the trajectory into the standing voltage potential along the mid-plane of the filter. As a function of drift distance along the length of the filter, the filter zooms in with exponentially increasing precision on the transverse velocity component of the electron kinetic energy. This yields a linear dimension for the total filter length that is exceptionally compact compared to previous techniques for electromagnetic filtering. The parallel velocity component of the electron kinetic energy oscillates in an electrostatic harmonic trap as the electron drifts along the length of the filter. An analysis of the phase-space volume conservation validates the expected behavior of the filter from the adiabatic invariance of the orbital magnetic moment and energy conservation following Liouville's theorem for Hamiltonian systems.

astro-ph.IM↗

arXiv2018

PTOLEMY: A Proposal for Thermal Relic Detection of Massive Neutrinos and Directional Detection of MeV Dark Matter

We propose to achieve the proof-of-principle of the PTOLEMY project to directly detect the Cosmic Neutrino Background (CNB). Each of the technological challenges described in [1,2] will be targeted and hopefully solved by the use of the latest experimental developments and profiting from the low background environment provided by the LNGS underground site. The first phase will focus on the graphene technology for a tritium target and the demonstration of TES microcalorimetry with an energy resolution of better than 0.05 eV for low energy electrons. These technologies will be evaluated using the PTOLEMY prototype, proposed for underground installation, using precision HV controls to step down the kinematic energy of endpoint electrons to match the calorimeter dynamic range and rate capabilities. The second phase will produce a novel implementation of the EM filter that is scalable to the full target size and which demonstrates intrinsic triggering capability for selecting endpoint electrons. Concurrent with the CNB program, we plan to exploit and develop the unique properties of graphene to implement an intermediate program for direct directional detection of MeV dark matter [3,4]. This program will evaluate the radio-purity and scalability of the graphene fabrication process with the goal of using recently identified ultra-high radio-purity CO2 sources. The direct detection of the CNB is a snapshot of early universe dynamics recorded by the thermal relic neutrino yield taken at a time that predates the epochs of Big Bang Nucleosynthesis, the Cosmic Microwave Background and the recession of galaxies (Hubble Expansion). Big Bang neutrinos are believed to have a central role in the evolution of the Universe and a direct measurement with PTOLEMY will unequivocally establish the extent to which these predictions match present-day neutrino densities.

physics.ins-det↗

arXiv2018

First Result on the Neutrinoless Double Beta Decay of $^{82}$Se with CUPID-0

We report the result of the search for neutrinoless double beta decay of $^{82}$Se obtained with CUPID-0, the first large array of scintillating Zn$^{82}$Se cryogenic calorimeters implementing particle identification. We observe no signal in a 1.83 kg yr $^{82}$Se exposure and we set the most stringent lower limit on the \onu $^{82}$Se half-life T$^{0ν}_{1/2}>$ 2.4$\times \mathrm{10}^{24}$ yr (90\% credible interval), which corresponds to an effective Majorana neutrino mass m$_{ββ} <$ (376-770) meV depending on the nuclear matrix element calculations. The heat-light readout provides a powerful tool for the rejection of \al\ particles and allows to suppress the background in the region of interest down to (3.6$^{+1.9}_{-1.4}$)$\times$10$^{-3}$\ckky, an unprecedented level for this technique.

nucl-ex↗

arXiv2018

CUPID-0: the first array of enriched scintillating bolometers for 0νββdecay investigations

The CUPID-0 detector hosted at the Laboratori Nazionali del Gran Sasso, Italy, is the first large array of enriched scintillating cryogenic detectors for the investigation of $^{82}$Se neutrinoless double-beta decay (0$νββ$). CUPID-0 aims at measuring a background index in the region of interest (RoI) for 0$νββ$ at the level of 10$^{-3}$ c/keV/kg/y, the lowest value ever measured using cryogenic detectors. This result can be achieved by a state of the art technology for background suppression and thorough protocols and procedures for detector preparation and construction. In this paper, the different phases of the detector design and construction will be presented, from the material selection (for the absorber production) to the new and innovative detector structure. The successful construction of the detector lead to promising detector performance which are here preliminarily discussed

physics.ins-det↗

arXiv2018

An innovative technique for the investigation of the 4-fold forbidden beta-decay of $^{50}$V

For the first time a Vanadium-based crystal was operated as cryogenic particle detector. The scintillating low temperature calorimetric technique was used for the characterization of a 22 g YVO$_4$ crystal aiming at the investigation of the 4-fold forbidden non-unique $β^-$ decay of $^{50}$V. The excellent bolometric performance of the compound together with high light output of the crystal makes it an outstanding technique for the study of such elusive rate process. The internal radioactive contaminations of the crystal are also investigated showing that an improvement on the current status of material selection and purification are needed, $^{235/238}$U and $^{232}$Th are measured at the level of 28 mBq/kg, 1.3 Bq/kg and 28 mBq/kg, respectively. In this work, we also discuss a future upgrade of the experimental set-up which may pave the road for the detection of the rare $^{50}$V $β^-$ decay.

physics.ins-det↗

arXiv2017

Production of 82Se enriched Zinc Selenide (ZnSe) crystals for the study of neutrinoless double beta decay

High purity Zinc Selenide (ZnSe) crystals are produced starting from elemental Zn and Se to be used for the search of the neutrinoless double beta decay (0νDBD) of 82Se. In order to increase the number of emitting nuclides, enriched 82Se is used. Dedicated production lines for the synthesis and conditioning of the Zn82Se powder in order to make it suitable for crystal growth were assembled compliant with radio-purity constraints specific to rare event physics experiments. Besides routine check of impurities concentration, high sensitivity measurements are made for radio-isotope concentrations in raw materials, reactants, consumables, ancillaries and intermediary products used for ZnSe crystals production. Indications are given on the crystals perfection and how it is achieved. Since very expensive isotopically enriched material (82Se) is used, a special attention is given for acquiring the maximum yield in the mass balance of all production stages. Production and certification protocols are presented and resulting ready-to-use Zn82Se crystals are described.

physics.ins-det↗