► The ZnMoO4 crystals permit alpha discrimination from the pulse shape analysis. ► ZnMoO4 crystals show an excellent energy resolution. ► ZnMoO4 crystals are extremely radiopure. ► A medium sized ...(30kg) tower-like double beta experiment based on ZnMoO4 will show a zero background in the ROI.
We investigate the performances of two ZnMoO4 scintillating crystals operated as bolometers, in view of a next generation experiment to search the neutrinoless double beta decay of 100Mo. We present the results of the α vs β/γ discrimination, obtained through the scintillation light as well as through the study of the shape of the thermal signal alone. The separation obtained at the 2615keV line of 208Tl is 8σ, using the heat-light scatter plot, while it exceeds 20σ using the shape of the thermal pulse alone. The achieved FWHM energy resolution ranges from 2.4keV (at 238keV) to 5.7keV (at 2615keV). The internal radioactive contaminations of the ZnMoO4 crystals were evaluated through a 407h background measurement. The obtained limit is <32μBq/kg for 228Th and 226Ra. These values were used for a Monte Carlo simulation aimed at evaluating the achievable background level of a possible, future array of enriched Zn100MoO4 crystals.
CUPID-0 is the first pilot experiment of CUPID, a next-generation project searching for neutrinoless double beta decay. In its first scientific run, CUPID-0 operated 26 ZnSe cryogenic calorimeters ...coupled to light detectors in the underground Laboratori Nazionali del Gran Sasso. In this work, we analyzed a ZnSe exposure of 11.34 kg year to search for the neutrinoless double beta decay of
70
Zn and for the neutrinoless positron-emitting electron capture of
64
Zn. We found no evidence for these decays and set 90
%
credible interval limits of
T
1
/
2
0
ν
β
β
(
70
Zn) > 1.6
10
21
year and
T
1
/
2
0
ν
E
C
β
+
(
64
Zn) > 1.2
×
10
22
year, surpassing by more than one order of magnitude the previous experimental results (Belli et al. in J Phys G 38(11):115107,
https://doi.org/10.1088/0954-3899/38/11/115107
, 2011).
.
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 22g 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 make 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 28mBq/kg, 1.3 Bq/kg and 28m Bq/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.
The neutron flux is a crucial parameter for the analysis of nuclear reactors, because it affects the reaction rate and thus the fuel burnup. Moreover, a very precise knowledge of the flux in the ...irradiation positions is helpful for benchmarking the simulation models of the reactor. In particular, an MCNP model of the TRIGA Mark II reactor installed at LENA (Laboratory of Applied Nuclear Energy) of the University of Pavia was developed in the recent years, describing the geometries and the materials of the whole reactor with very good accuracy.
In this article, we present the results of the neutron flux measurements in four irradiation positions. The neutron activation technique was used to perform an absolute measurement of the flux. Various samples containing a known amount of elements were irradiated in the reactor facilities and the activation rate of a large number of isotopes was measured through γ-ray spectroscopy with very low background HPGe detectors. In order to accurately calculate the activation rate, Monte Carlo codes based on GEANT4 were developed to evaluate the γ-ray detection efficiency for every radioisotope of interest. The samples were measured with three different HPGe detectors and the measurements were repeated in various geometric configurations in order to assess the reliability and repeatability of this analysis technique.
The MCNP reactor model was used to evaluate the energetic neutron flux distributions in the irradiation positions. The effective activation cross sections were computed from these distributions, testing the dependence on the MCNP simulation results.
Finally, the neutron flux was calculated from the data of activation rate and effective cross section of each isotope. The good agreement in the results of the flux calculations from the many different activated samples confirms the reliability of the adopted methodology.
•Neutron activation technique is used to measure the flux in different TRIGA reactor facilities.•The γ-ray measurement efficiency is evaluated through GEANT4 Monte Carlo simulations.•Measurements with different HPGe detectors to check the analysis accuracy and repeatability.•Neutron flux evaluated from the experimental data of 30 different activated isotopes.
The CUORE Cryostat D’Addabbo, A.; Alduino, C.; Bersani, A. ...
Journal of low temperature physics,
12/2018, Letnik:
193, Številka:
5-6
Journal Article
Recenzirano
Odprti dostop
The Cryogenic Underground Observatory for Rare Events (CUORE) is a bolometric experiment for neutrinoless double-beta decay in
130
Te
search, currently taking data at the underground facility of ...Laboratori Nazionali del Gran Sasso (LNGS). The CUORE cryostat successfully cooled down a mass of about 1 ton at
∼
7
mK
, delivering a uniform and constant base temperature. This result marks a fundamental milestone in low-temperature detector techniques, opening the path for future ton-scale bolometric experiments searching for rare events. In this paper, we present the CUORE cryogenic infrastructure, briefly describing its critical subsystems.
•The first successful growth and processing at large scale of Zn82Se crystals is described.•Zn82Se crystals are compliant with harsh radio-purity requests of 0νDBD experiments.•Zn82Se crystals have ...good scintillating bolometer performance for 0νDBD application.•Guidelines for crystal production of upcoming one-ton 0νDBD experiment(s) are given.
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.
The CUPID-0 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
Se and two ...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
Se into the 0
, 2
and 2
excited states of
Kr with an exposure of 5.74 kg
yr (2.24
10
emitters
yr). We found no evidence of the decays and set the most stringent limits on the widths of these processes:
(
Se
Kr
)8.55
10
yr
,
(
Se
Kr
)
yr
,
(
Se
Kr
)8.25
10
yr
(90
credible interval).
Large-mass bolometers are today extensively used for dark matter and double beta decay searches, in both cases the ultimate experimental sensitivity is defined by the background level reached in such ...devices. The most common background sources and the techniques used for their identification and reduction are here reviewed, with a particular focus on double beta decay searches. The relevant role played by Monte Carlo simulations in this field is discussed. As a real case, the background optimization in the MiDBD experiment is described.
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