ZnSe scintillating bolometers are good candidates for future Double Beta Decay searches, because of the
82Se high Q-value and thanks to the possibility of alpha background rejection on the basis of ...the scintillation signal. In this paper we report the characteristics and the anomalies observed in an extensive study of these devices. Among them, an unexpected high emission from alpha particles, accompanied with an unusual pattern of the light vs. heat scatter plot. The perspectives for the application of this kind of detectors to search for the Neutrinoless Double Beta Decay of
82Se are presented.
•The growth conditions to produce a ZnWO4:Sm single crystals were determined.•The Sm3+ segregation coefficient in the ZnWO4 single crystal was estimated to be 0.023.•The effect of Sm3 + segregation ...on the ZnWO4 crystal lattice parameters has been investigated.•ZnWO4:148,149Sm crystals were obtained following the established growth technique.
The growth conditions to produce a high quality ZnWO4:Sm single crystals by the Czochralski method were determined in this work. The role of the Sm impurity in the formation of bubbles in a ZnWO4 single crystal is discussed. The Sm3+ ions segregation coefficient in the ZnWO4 single crystal was estimated to be 0.023. The effect of non-isomorphic substitution of Sm3 + for Zn2 + ions on the ZnWO4 crystal lattice parameters has been investigated. The X-ray luminescence spectra of ZnWO4:Sm3+ crystals are discussed. Two ZnWO4 crystals doped with samarium enriched in 148Sm and 149Sm isotopes were obtained following the established growth technique, which demonstrates its feasibility and reliability for production of detector for rare nuclear processes studies.
As experiments searching for neutrinoless double beta decay push into the inverted hierarchy, enriched isotope target masses of hundreds of kilograms are required. Due to unavoidable losses ...throughout the entire production chain, the recovery of expensive enriched material used in crystal-based experiments should be given special attention. The CUPID-0 experiment using Zn82Se scintillating bolomoters provides a unique opportunity at the 10-kg-scale to test a recovery process for enriched 82Se. We present a multi-stage, high-yield method consisting of wet chemistry and vacuum distillation. The chemical purity, isotopic abundance, and radiopurity is demonstrated to be preserved after the 82Se extraction with recovery efficiency no less than 86.4% (that potentially can be higher than 94.7%) and chemical purity of 99.999%.
CUORE, an array of 988 TeO
2
bolometers, is about to be one of the most sensitive experiments searching for neutrinoless double-beta decay. Its sensitivity could be further improved by removing the ...background from
α
radioactivity. A few years ago it was pointed out that the signal from
β
s can be tagged by detecting the emitted Cherenkov light, which is not produced by
α
s. In this paper we confirm this possibility. For the first time we measured the Cherenkov light emitted by a CUORE crystal, and found it to be 100 eV at the
Q
-value of the decay. To completely reject the
α
background, we compute that one needs light detectors with baseline noise below 20 eV RMS, a value which is 3–4 times smaller than the average noise of the bolometric light detectors we are using. We point out that an improved light detector technology must be developed to obtain TeO
2
bolometric experiments able to probe the inverted hierarchy of neutrino masses.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The LUCIFER project aims at deploying the first array of enriched scintillating bolometers for the investigation of neutrinoless double-beta decay of Formula: see textSe. The matrix which embeds the ...source is an array of ZnSe crystals, where enriched Formula: see textSe is used as decay isotope. The radiopurity of the initial components employed for manufacturing crystals, that can be operated as bolometers, is crucial for achieving a null background level in the region of interest for double-beta decay investigations. In this work, we evaluated the radioactive content in 2.5 kg of 96.3 % enriched Formula: see textSe metal, measured with a high-purity germanium detector at the Gran Sasso deep underground laboratory. The limits on internal contaminations of primordial decay chain elements of Formula: see textTh, Formula: see textU and Formula: see textU are respectively: Formula: see text61, Formula: see text110 and Formula: see text74 Formula: see textBq/kg at 90 % C.L. The extremely low-background conditions in which the measurement was carried out and the high radiopurity of the Formula: see textSe allowed us to establish the most stringent lower limits on the half-lives of the double-beta decay of Formula: see textSe to 0Formula: see text, 2Formula: see text and 2Formula: see text excited states of Formula: see textKr of 3.4Formula: see text10Formula: see text, 1.3Formula: see text10Formula: see text and 1.0Formula: see text10Formula: see text y, respectively, with a 90 % C.L.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Localization and modeling of radioactive contaminations is a challenge that ultra-low background experiments are constantly facing. These are fundamental steps both to extract scientific results and ...to further reduce the background of the detectors. Here we present an innovative technique based on the analysis of
α
-
α
delayed coincidences in
232
Th and
238
U decay chains, developed to investigate the contaminations of the ZnSe crystals in the CUPID-0 experiment. This method allows to disentangle surface and bulk contaminations of the detectors relying on the different probability to tag delayed coincidences as function of the
α
decay position.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Recently there is a flourishing and notable interest in the crystalline scintillator material sodium iodide (NaI) as target for direct dark matter searches. This is mainly driven by the long-reigning ...contradicting situation in the dark matter sector: the positive evidence for the detection of a dark matter modulation signal claimed by the DAMA/LIBRA collaboration is (under so-called standard assumptions) inconsistent with the null-results reported by most of the other direct dark matter experiments. We present the results of a first prototype detector using a new experimental approach in comparison to conventional single-channel NaI scintillation light detectors: a NaI crystal operated as a scintillating calorimeter at milli-Kelvin temperatures simultaneously providing a phonon (heat) plus scintillation light signal and particle discrimination on an event-by-event basis. We evaluate energy resolution, energy threshold and further performance parameters of this prototype detector developed within the COSINUS R&D project.
Bolometers have proven to be good detectors for the search of neutrinoless double betadecay. By operating at cryogenic temperatures, they feature excellent energy resolution and lowbackground. The ...detection of the possible light emitted when particles interact in the bolometeris a promising method to lower the background of the experiments. The different amount of lightemitted in beta / gamma and alpha interactions, whether due to scintillation or Cerenkov emission, allows todiscriminate the two interaction types. Because of the cryogenic environment, light detectors areoften bolometers. In this work we present a software algorithm to lower the energy threshold ofbolometric light detectors coupled to luminescent bolometers. The application to data from Ge lightdetectors coupled to ZnMoO sub(4) and TeO sub(2) bolometers shows that the energy threshold can be loweredsubstantially, increasing the discrimination power when the amount of emitted light is small.
Bolometers have proven to be very good detectors to search for rare processes thanks to their excellent energy resolution and their low intrinsic background. Further active background rejection can ...be obtained by the simultaneous readout of the heat and light signals produced by particles interacting in scintillating bolometers, as proposed by the LUCIFER experiment. In this framework, the choice of the light detector and the optimization of its working conditions play a crucial role. In this paper, we report a study of the performances of a Germanium bolometric light detector in terms of signal amplitude, energy resolution and signal time development. The impact of various operational parameters on the detector performances is discussed.
► Particle identification allows to reduce background in rare process studies. ► Pulse shape analysis can be used in some bolometers to identify the nature of the interacting particle. ► This feature ...was observed in different scintillating crystals (CaMoO
4, ZnMoO
4, MgMoO
4 and ZnSe).
We report in this paper the proofs that the pulse shape analysis can be used in some bolometers to identify the nature of the interacting particle. Indeed, while detailed analyses of the signal time development in purely thermal detectors have not produced so far interesting results, similar analyses on bolometers built with scintillating crystals seem to show that it is possible to distinguish between an electron or
γ-ray and an
α particle interaction. This information can be used to eliminate background events from the recorded data in many rare process studies, especially Neutrinoless Double Beta decay search. Results of pulse shape analysis of signals from a number of bolometers with absorbers of different composition (CaMoO
4, ZnMoO
4, MgMoO
4 and ZnSe) are presented and the pulse shape discrimination capability of such detectors is discussed.
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