A search for alpha and double beta decays of ytterbium isotopes was performed with an ultra low-background high purity germanium detector at Gran Sasso Underground Laboratory (Italy). A 194.7 g Yb
2
...(C
2
O
4
)
3
powder sample was measured for 11.3 days with a total Yb exposure of 1.25 kg
×
day. Half-life limits for
α
-decay modes of
168
Y
b
,
170
Y
b
,
171
Y
b
,
172
Y
b
,
173
Y
b
,
174
Y
b
and
176
Y
b
into the first excited states have been obtained between
6
×
10
14
years and
2
×
10
16
years. These are the first experimental constraints of these decay modes. Double electron capture of
168
Y
b
and double beta decay of
176
Y
b
into the first excited 2
+
and 0
+
states could be excluded with limits between
1
×
10
14
years to
8
×
10
16
years. This improves the experimental information on some of the decay modes compared to previous constraints.
A 510 day long-term measurement of a 45.3 g platinum foil acting as the sample and high voltage contact in an ultra-low-background high purity germanium detector was performed at Laboratori Nazionali ...del Gran Sasso (Italy). The data was used for a detailed study of double beta decay modes in natural platinum isotopes. Limits are set in the range
O
(
10
14
-
10
19
)
years (90% C.L.) for several double beta decay transitions to excited states confirming, and partially extending existing limits. The highest sensitivity of the measurement, greater than
10
19
years, was achieved for the two neutrino and neutrinoless double beta decay modes of the isotope
198
Pt. Additionally, novel limits for inelastic dark matter scattering on
195
Pt are placed up to mass splittings of approximately 500 keV. We analyze several techniques to extend the sensitivity and propose a few approaches for future medium-scale experiments with platinum-group elements.
Background model of the CUPID-0 experiment Azzolini, O.; Beeman, J. W.; Bellini, F. ...
The European physical journal. C, Particles and fields,
07/2019, Letnik:
79, Številka:
7
Journal Article
Recenzirano
Odprti dostop
CUPID-0 is the first large mass array of enriched Zn
82
Se scintillating low temperature calorimeters, operated at LNGS since 2017. During its first scientific runs, CUPID-0 collected an exposure of ...9.95 kg year. Thanks to the excellent rejection of
α
particles, we attained the lowest background ever measured with thermal detectors in the energy region where we search for the signature of
82
Se
neutrinoless double beta decay. In this work we develop a model to reconstruct the CUPID-0 background over the whole energy range of experimental data. We identify the background sources exploiting their distinctive signatures and we assess their extremely low contribution down to
∼
10
-
4
counts/(keV kg year) in the region of interest for
82
Se
neutrinoless double beta decay search. This result represents a crucial step towards the comprehension of the background in experiments based on scintillating calorimeters and in next generation projects such as CUPID.
The R&D project COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) aims to develop a cryogenic scintillating calorimeter using an undoped NaI-crystal as ...target for direct dark matter search. Dark matter particles interacting with the detector material generate both a phonon signal and scintillation light. While the phonon signal provides a precise determination of the deposited energy, the simultaneously measured scintillation light allows for particle identification on an event-by-event basis, a powerful tool to study material-dependent interactions, and to suppress backgrounds. Using the same target material as the DAMA/LIBRA collaboration, the COSINUS technique may offer a unique possibility to investigate and contribute information to the presently controversial situation in the dark matter sector. We report on the dedicated design planned for the NaI proof-of-principle detector and the objectives of using this detection technique in the light of direct dark matter detection.
A first search for rare decays of gadolinium isotopes was performed with an ultra-low background high-purity germanium detector at Gran Sasso Underground Laboratory (Italy). A 198 g
Gd
2
O
3
powder ...sample was measured for 63.8 d with a total Gd exposure of 12.6 kg
×
d.
152
Gd is the most promising isotope for resonant enhanced neutrinoless double electron capture which could significantly increase the decay rate over other neutrinoless double beta decay processes. The half-life for this decay was constrained to
>
4.2
×
10
12
year (90% credibility). This limit is still orders of magnitude away from theoretical predictions but it is the first established limit on the transition paving the way for future experiments. In addition, other rare alpha and double beta decay modes were investigated in
152
Gd,
154
Gd, and
160
Gd with half-life limits in the range of
10
17
-
20
year.
•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.
The scintillation properties of cesium-zirconium hexachloride (Cs2ZrCl6) were investigated by γ-ray spectrometry and the Compton Coincidence Technique. The tested cylindrical sample had 20 mm ...diameter and 12 mm height. The crystal shows a high light output of 40 900 photons per MeV as measured by a spectroscopy type photomultiplier with 20 μs pulse integration time under γ-ray excitation at room temperature. A small deviation from linear response as a function of energy deposited in γ-ray absorption or Compton scattering processes, combined with a high light yield, results in good energy resolution equal to 4.3 % at 662 keV and 2.3 % at 2.6 MeV. Due to long lasting scintillation decay the sample properties were studied at different shaping time constants in an analogue spectroscopy chain or using different integration time gates when employing a digital analyzer.
Residual radioactive contaminants of a caesium hafnium chloride (Cs2HfCl6) crystal scintillator have been measured in a low background setup at the Gran Sasso National Laboratory of the INFN, Italy. ...The total alpha activity of the detector is at the level of 7.8(3) mBq/kg. The results of direct studies of the α decay of naturally occurring Hf isotopes that have been performed using the “source=detector” approach are presented. In 2848 h of data taking, the α decay of 174Hf was observed with T=1/2(7.0±1.2)×1016 y.
As one of the primordial radioactive isotopes, Formula omitted mainly undergoes Formula omitted-decay with a half-life of Formula omitted years. However, it is also one of 35 double beta decay ...candidates in which the single Formula omitted-decay is forbidden or strongly suppressed. 181 mg of thorium contained in a gas mantle were measured in a HPGe well-detector at the Gran Sasso Underground Laboratory with a total exposure of 3.25 g Formula omittedd. We obtain half-life limits on all double beta decay modes of Formula omitted to excited states of Formula omitted on the order of Formula omitted years. For the most likely transition into the 0 Formula omitted state we find a lower half-life limit of Formula omitted years (90% C.I.). These are the first constraints on double beta decay excited state transition in Formula omitted.
First limits on double beta decays in 232Th Laubenstein, M.; Lehnert, B.; Nagorny, S. S.
The European physical journal. C, Particles and fields,
08/2020, Letnik:
80, Številka:
8
Journal Article
Recenzirano
Odprti dostop
As one of the primordial radioactive isotopes,
232
Th
mainly undergoes
α
-decay with a half-life of
1.402
·
10
10
years. However, it is also one of 35 double beta decay candidates in which the ...single
β
-decay is forbidden or strongly suppressed. 181 mg of thorium contained in a gas mantle were measured in a HPGe well-detector at the Gran Sasso Underground Laboratory with a total exposure of 3.25 g
×
d.
We obtain half-life limits on all double beta decay modes of
232
Th
to excited states of
232
U
on the order of
10
11
-
15
years. For the most likely transition into the 0
1
+
state we find a lower half-life limit of
6.7
·
10
14
years (90% C.I.). These are the first constraints on double beta decay excited state transition in
232
Th
.
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