546 research outputs found
An innovative technique for the investigation of the 4-fold forbidden beta-decay of 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 crystal aiming at the
investigation of the 4-fold forbidden non-unique decay of 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, U and 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 V decay
Cryogenic light detectors with enhanced performance for rare events physics
We have developed and tested a new way of coupling bolometric light detectors
to scintillating crystal bolometers based upon simply resting the light
detector on the crystal surface, held in position only by gravity. This
straightforward mounting results in three important improvements: (1) it
decreases the amount of non-active materials needed to assemble the detector,
(2) it substantially increases the light collection efficiency by minimizing
the light losses induced by the mounting structure, and (3) it enhances the
thermal signal induced in the light detector thanks to the extremely weak
thermal link to the thermal bath. We tested this new technique with a 16 cm
Ge light detector with thermistor readout sitting on the surface of a large
TeO bolometer. The light collection efficiency was increased by greater
than 50\% compared to previously tested alternative mountings. We obtained a
baseline energy resolution on the light detector of 20~eV RMS that, together
with increased light collection, enabled us to obtain the best vs
discrimination ever obtained with massive TeO crystals. At
the same time we achieved rise and decay times of 0.8 and 1.6 ms, respectively.
This superb performance meets all of the requirements for the CUPID (CUORE
Upgrade with Particle IDentification) experiment, which is a 1-ton
scintillating bolometer follow up to CUORE.Comment: 6 pages, 4 figure
How dangerous are your smartphones? App usage recommendation with privacy preserving
With the rapid proliferation of mobile devices, explosive mobile applications (apps) are developed in the past few years. However, the functions of mobile apps are varied and the designs of them are not well understood by end users, especially the activities and functions related to user privacy. Therefore, understanding how much danger of mobile apps with respect to privacy violation to mobile users is becomes a critical issue when people use mobile devices. In this paper, we evaluate the mobile app privacy violation of mobile users by computing the danger coefficient. In order to help people reduce the privacy leakage, we combine both the user preference to mobile apps and the privacy risk of apps and propose a mobile app usage recommendation method named AppURank to recommend the secure apps with the same function as the âdangerousâ one for people use. The evaluation results show that our recommendation can reduce the privacy leakage by 50%
Background suppression in massive TeO bolometers with Neganov-Luke amplified light detectors
Bolometric detectors are excellent devices for the investigation of
neutrinoless double-beta decay (0). The observation of such
decay would demonstrate the violation of lepton number, and at the same time it
would necessarily imply that neutrinos have a Majorana character. The
sensitivity of cryogenic detectors based on TeO is strongly limited by the
alpha background in the region of interest for the 0 of
Te. It has been demonstrated that particle discrimination in TeO
bolometers is possible measuring the Cherenkov light produced by particle
interactions. However an event-by-event discrimination with NTD-based light
detectors has to be demonstrated. We will discuss the performance of a
highly-sensitive light detector exploiting the Neganov-Luke effect for signal
amplification. The detector, being operated with NTD-thermistor and coupled to
a 750 g TeO crystal, shows the ability for an event-by-event identification
of electron/gamma and alpha particles. The extremely low detector baseline
noise, RMS 19 eV, demonstrates the possibility to enhance the sensitivity of
TeO-based 0 experiment to an unprecedented level
TeO bolometers with Cherenkov signal tagging: towards next-generation neutrinoless double beta decay experiments
CUORE, an array of 988 TeO 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
radioactivity. A few years ago it has been pointed out that the signal from
s can be tagged by detecting the emitted Cherenkov light, which is not
produced by 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 -value of the decay. To completely reject the
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 bolometric experiments
able to probe the inverted hierarchy of neutrino masses.Comment: 5 pages, 4 figures. Added referee correction
New experimental limits on the alpha decays of lead isotopes
For the first time a PbWO4 crystal was grown using ancient Roman lead and it
was run as a cryogenic detector. Thanks to the simultaneous and independent
read-out of heat and scintillation light, the detector was able to discriminate
beta/gamma interactions with respect to alpha particles down to low energies.
New more stringent limits on the alpha decays of the lead isotopes are
presented. In particular a limit of T_{1/2} > 1.4*10^20 y at a 90% C.L. was
evaluated for the alpha decay of 204Pb to 200Hg
Development of a Li2MoO4 scintillating bolometer for low background physics
We present the performance of a 33 g Li2MoO4 crystal working as a
scintillating bolometer. The crystal was tested for more than 400 h in a
dilution refrigerator installed in the underground laboratory of Laboratori
Nazionali del Gran Sasso (Italy). This compound shows promising features in the
frame of neutron detection, dark matter search (solar axions) and neutrinoless
double-beta decay physics. Low temperature scintillating properties were
investigated by means of different alpha, beta/gamma and neutron sources, and
for the first time the Light Yield for different types of interacting particle
is estimated. The detector shows great ability of tagging fast neutron
interactions and high intrinsic radiopurity levels (< 90 \muBq/kg for 238-U and
< 110 \muBq/kg for 232-Th).Comment: revised versio
First bolometric measurement of the two neutrino double beta decay of Mo with a ZnMoO crystals array
The large statistics collected during the operation of a ZnMoO array, for
a total exposure of 1.3 kg day of Mo, allowed the first
bolometric observation of the two neutrino double beta decay of Mo. The
observed spectrum of each crystal was reconstructed taking into account the
different background contributions due to environmental radioactivity and
internal contamination. The analysis of coincidences between the crystals
allowed the assignment of constraints to the intensity of the different
background sources, resulting in a reconstruction of the measured spectrum down
to an energy of 300 keV. The half-life extracted from the data is
T= [7.15 0.37 (stat) 0.66 (syst)] 10
y.Comment: 6 pages, 2 figure, Accepted for publication in Journal of Physics G:
Nuclear and Particle Physic
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