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 for 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.
RES-NOVA is a newly proposed experiment for detecting neutrinos from astrophysical sources, mainly Supernovae, using an array of cryogenic detectors made of PbWO
4
crystals produced from ...archaeological Pb. This unconventional material, characterized by intrinsic high radiopurity, enables low-background levels in the region of interest for the neutrino detection via Coherent Elastic neutrino-Nucleus Scattering (CE
ν
NS). This signal lies at the detector energy threshold,
O
(1 keV), and it is expected to be hidden by naturally occurring radioactive contaminants of the crystal absorber. Here, we present the results of a radiopurity assay on a 0.84 kg PbWO
4
crystal produced from archaeological Pb operated as a cryogenic detector. The crystal internal radioactive contaminations are:
232
Th <40
μ
Bq/kg,
238
U <30
μ
Bq/kg,
226
Ra 1.3 mBq/kg and
210
Pb 22.5 mBq/kg. We also present a background projection for the final experiment and possible mitigation strategies for further background suppression. The achieved results demonstrate the feasibility of realizing this new class of detectors.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Scintillating bolometers of ZnSe are the baseline choice of the LUCIFER experiment, whose aim is to observe the neutrinoless double beta decay of super(82)Se. The independent read-out of the heat and ...scintillation signals allows to identify and reject a particle interactions, the dominant background source for bolometric detectors. In this paper we report the performances of a ZnSe crystal operated within the LUCIFER R&D. We measured the scintillation yield, the energy resolution and the background in the energy region where the signal from 0nDBD decay of super(82)Se is expected with an exposure of 9.4kg times days. With a newly developed analysis algorithm we improved the rejection of alpha events, and we estimated the increase in energy resolution obtained by the combination of the heat and light signals. For the first time we measured the light emitted by nuclear recoils, and found it to be compatible with zero. We conclude that the discrimination of nuclear recoils from beta / gamma interactions in the WIMPs energy region is possible, but low-noise light detectors are needed.
The LUCIFER project aims at deploying the first array of enriched scintillating bolometers for the investigation of neutrinoless double-beta decay of Se-82. The matrix which embeds the source is an ...array of ZnSe crystals, where enriched Se-82 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 Se-82 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 Th-232, U-238 and U-235 are respectively: <61,<110 and <74 mu Bq/kg at 90 % C.L. The extremely low-background conditions in which the measurement was carried out and the high radiopurity of the Se-82 allowed us to establish the most stringent lower limits on the half-lives of the double-beta decay of Se-82 to 0(+)(1), 2(2)(+) and 2(1)(+) excited states of Kr-82 of 3.4.10(22), 1.3.10(22) and 1.0.10(22) y, respectively, with a 90 % C.L.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The first detailed study on the performance of a ZnO-based cryogenic scintillating bolometer as a detector to search for rare processes in zinc isotopes was performed. A 7.2 g ZnO low-temperature ...detector, containing more than 80% of zinc in its mass, exhibits good energy resolution of baseline noise 1.0--2.7 keV FWHM at various working temperatures resulting in a low-energy threshold for the experiment, 2.0--6.0 keV. The light yield for $\beta$/$\gamma$ events was measured as 1.5(3) keV/MeV, while it varies for $\alpha$ particles in the range of 0.2--3.0 keV/MeV. The detector demonstrate an effective identification of the $\beta$/$\gamma$ events from $\alpha$ events using time-properties of only heat signals. %(namely, Rise time parameter). The radiopurity of the ZnO crystal was evaluated using the Inductively Coupled Plasma Mass Spectrometry, an ultra-low-background High Purity Ge $\gamma$-spectrometer, and bolometric measurements. Only limits were set at the level of $\mathcal{O}$(1--100) mBq/kg on activities of \Nuc{K}{40}, \Nuc{Cs}{137} and daughter nuclides from the U/Th natural decay chains. The total internal $\alpha$-activity was calculated to be 22(2) mBq/kg, with a major contribution caused by 6(1) mBq/kg of \Nuc{Th}{232} and 12(2) mBq/kg of \Nuc{U}{234}. Limits on double beta decay (DBD) processes in \Nuc{Zn}{64} and \Nuc{Zn}{70} isotopes were set on the level of $\mathcal{O}(10^{17}$--$10^{18})$ yr for various decay modes profiting from 271 h of acquired background data in the above-ground lab. This study shows a good potential for ZnO-based scintillating bolometers to search for DBD processes of Zn isotopes, especially in \Nuc{Zn}{64}, with the most prominent spectral features at $\sim$10--20 keV, like the two neutrino double electron capture. A 10 kg-scale experiment can reach the experimental sensitivity at the level of $\mathcal{O}(10^{24})$ yr.
Rare event physics demands very detailed background control, high-performance detectors, and custom analysis strategies. Cryogenic calorimeters combine all these ingredients very effectively, ...representing a promising tool for next-generation experiments. CUPID-0 is one of the most advanced examples of such a technique, having demonstrated its potential with several results obtained with limited exposure. In this paper, we present a further application. Exploiting the analysis of delayed coincidence, we can identify the signals caused by the 220Rn-216Po decay sequence on an event-by-event basis. The analysis of these events allows us to extract the time differences between the two decays, leading to a new evaluation of 216Po half-life, estimated as (143.3±2.8) ms.
The production of ultra-pure raw material is a crucial step to ensure the required background level in rare event searches. In this work, we establish an innovative technique developed to produce ...high-purity (99.999%) granular zinc. We demonstrate the effectiveness of the refining procedure by measuring the internal contaminations of the purified zinc with a high-purity germanium detector at the Laboratori Nazionali del Gran Sasso. The total activity of cosmogenic activated nuclides is measured at the level of a few mBq/kg, as well as limits on naturally occurring radionuclides are set to less than mBq/kg. The excellent radiopurity of the zinc sample allows us to search for electron capture with positron emission and neutrinoless double electron capture of
64
Zn, setting the currently most stringent lower limits on their half-lives,
T
1
/
2
ε
β
+
>
2.7
×
10
21
year
(90% CI), and
T
1
/
2
0
ν
2
ε
>
2.6
×
10
21
year
(90% CI), respectively.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We present the results obtained in the development of scintillating double-beta-decay bolometers. Several Mo and Cd based crystals were tested with the bolometric technique. The scintillation light ...was measured through a second independent bolometer. A 140-g CdWO4 crystal was run in a 417-h live time measurement. Thanks to the scintillation light, the α background is easily discriminated, resulting in zero counts above the 2615-keV γ line of 208Tl. These results, combined with an extreme easy light detector operation, represent the first tangible proof demonstrating the feasibility of this kind of technique.
Non-equilibrium quasiparticles can deteriorate the performance of superconducting qubits by reducing their coherence. We are investigating a source of quasiparticles that has been too long neglected, ...namely radioactivity: cosmic rays, environmental radioactivity and contaminants in the materials can all generate phonons of energy sufficient to break Cooper pairs and thus increase the number of quasiparticles. In this contribution, we describe the status of the project and its perspectives.
Core-collapse Supernovae (SNe) are one of the most energetic events in the Universe, during which almost all the star's binding energy is released in the form of neutrinos. These particles are direct ...probes of the processes occurring in the stellar core and provide unique insights into the gravitational collapse. RES-NOVA will revolutionize how we detect neutrinos from astrophysical sources, by deploying the first ton-scale array of cryogenic detectors made from archaeological lead. Pb offers the highest neutrino interaction cross-section via coherent elastic neutrino-nucleus scattering (CEνNS). Such process will enable RES-NOVA to be equally sensitive to all neutrino flavours. For the first time, we propose the use archaeological Pb as sensitive target material in order to achieve an ultra-low background level in the region of interest (O(1 keV)). All these features make possible the deployment of the first cm-scale neutrino telescope for the investigation of astrophysical sources. In this contribution, we will characterize the radiopurity level and the performance of a small-scale proof-of-principle detector of RES-NOVA, consisting in a PbWO
crystal made from archaeological-Pb operated as cryogenic detector.
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