384 research outputs found
Response of CdWO4 crystal scintillator for few MeV ions and low energy electrons
The response of a CdWO4 crystal scintillator to protons, alpha particles, Li,
C, O and Ti ions with energies in the range 1 - 10 MeV was measured. The
non-proportionality of CdWO4 for low energy electrons (4 - 110 keV) was studied
with the Compton Coincidence Technique. The energy dependence of the quenching
factors for ions and the relative light yield for low energy electrons was
calculated using a semi-empirical approach. Pulse-shape discrimination ability
between gamma quanta, protons, alpha particles and ions was investigated.Comment: 20 pages, 8 figs, accepted in Nucl. Instrum. Meth.
The event generator DECAY4 for simulation of double beta processes and decay of radioactive nuclei
The computer code DECAY4 is developed to generate initial energy, time and
angular distributions of particles emitted in radioactive decays of nuclides
and nuclear (atomic) deexcitations. Data for description of nuclear and atomic
decay schemes are taken from the ENSDF and EADL database libraries. The
examples of use of the DECAY4 code in several underground experiments are
described.Comment: 8 pages, 1 fi
Search for double beta decay of Zinc and Tungsten with the help of low-background ZnWO4 crystal scintillators
Double beta processes in 64-Zn, 70-Zn, 180-W, and 186-W have been searched
for with the help of large volume (0.1-0.7 kg) low background ZnWO4 crystal
scintillators at the Gran Sasso National Laboratories of the INFN. Total time
of measurements exceeds 10 thousands hours. New improved half-life limits on
double electron capture and electron capture with positron emission in 64-Zn
have been set, in particular (all the limits are at 90% C.L.): T1/2(0nu2EC)>
1.1e20 yr, T1/2(2nuECbeta+)>7.0e20 yr, and T1/2(0nuECbeta+)>4.3e20 yr. The
different modes of double beta processes in 70-Zn, 180-W, and 186-W have been
restricted at the level of 1e17-1e20 yr.Comment: 20 p., submitted to Phys. Rev.
Search for decay of Eu to the first excited level of Pm using underground -ray spectrometry
The alpha decay of Eu to the first excited level of Pm
(, keV) was searched for at the HADES underground
laboratory ( m w.e.). A sample of high purity europium oxide with
mass of 303 g and a natural isotopic composition has been measured over 2232.8
h with a high energy resolution ultra-low background n-type semi-planar HPGe
detector (40 cm) with sub-micron deadlayer. The new improved half-life
limit has been set as yr at 68% C.L.
Possibilities to improve the sensitivity of the experiment, which is already
near the theoretical predictions, are discussed. New half-life limit for
decay of Eu is also set as
yr.Comment: 11 pages, 5 figures, 2 tables, 18 reference
Quest for double beta decay of 160-Gd and Ce isotopes
The double beta decay study of 160-Gd has been performed in the Solotvina
Underground Laboratory with the help of Gd_2SiO_5(Ce) crystal scintillator
(volume 95 cc). The background of the detector in the vicinity of the 2 beta
energy of 160-Gd was reduced to 1.0 cpd/keV kg. The new improved half-life
limits have been established for neutrinoless 2 beta decay of 160-Gd to the
ground and first excited levels of 160-Dy: T1/2 > 2.3(1.3)E21 yr at 68%(90%)
C.L. The T1/2 bounds have been also set for two neutrino mode as well as for 2
beta decay with Majorons emission. Also the limits were established for
different 2 beta decay processes in 136-Ce, 138-Ce and 142-Ce.Comment: 12 pages, 6 figures, submitted to Nucl. Phys.
Optimization of light collection from crystal scintillators for cryogenic experiments
High light collection efficiency is an important requirement in any
application of scintillation detectors. The purpose of this study is to
investigate the possibility for improving this parameter in cryogenic
scintillation bolometers, which can be considered as a promising detectors in
experiments investigating neutrinoless double beta decay and dark matter.
Energy resolutions and relative pulse amplitudes of scintillation detectors
using ZnWO4 scintillation crystals of different shapes (cylinder 20 mm in
dimater by 20 mm and hexagonal prism with diagonal 20 mm and height 20 mm),
reflector materials and shapes, optical contact and surface properties
(polished and diffused) were measured at room temperature. Propagation of
optical photons in these experimental conditions was simulated using Geant4 and
ZEMAX codes. The results of the simulations are found to be in good agreement
with each other and with direct measurements of the crystals. This could be
applied to optimize the geometry of scintillation detectors used in the
cryogenic experiments.Comment: 12 pages, 8 figures, 1 Tabl
Rejection of randomly coinciding events in ZnMoO scintillating bolometers
Random coincidence of events (particularly from two neutrino double beta
decay) could be one of the main sources of background in the search for
neutrinoless double beta decay with cryogenic bolometers due to their poor time
resolution. Pulse-shape discrimination by using front edge analysis, mean-time
and methods was applied to discriminate randomly coinciding events in
ZnMoO cryogenic scintillating bolometers. These events can be effectively
rejected at the level of 99% by the analysis of the heat signals with rise-time
of about 14 ms and signal-to-noise ratio of 900, and at the level of 92% by the
analysis of the light signals with rise-time of about 3 ms and signal-to-noise
ratio of 30, under the requirement to detect 95% of single events. These
rejection efficiencies are compatible with extremely low background levels in
the region of interest of neutrinoless double beta decay of Mo for
enriched ZnMoO detectors, of the order of counts/(y keV kg).
Pulse-shape parameters have been chosen on the basis of the performance of a
real massive ZnMoO scintillating bolometer. Importance of the
signal-to-noise ratio, correct finding of the signal start and choice of an
appropriate sampling frequency are discussed
Impact of geometry on light collection efficiency of scintillation detectors for cryogenic rare event searches
Simulations of photon propagation in scintillation detectors were performed
with the aim to find the optimal scintillator geometry, surface treatment, and
shape of external reflector in order to achieve maximum light collection
efficiency for detector configurations that avoid direct optical coupling, a
situation that is commonly found in cryogenic scintillating bolometers in
experimental searches for double beta decay and dark matter. To evaluate the
light collection efficiency of various geometrical configurations we used the
ZEMAX ray-tracing software. It was found that scintillators in the shape of a
triangular prism with an external mirror shaped as truncated cone gives the
highest light collection efficiency. The results of the simulations were
confirmed by carrying out measurements of the light collection efficiencies of
CaWO4 crystal scintillators. A comparison of simulated and measured values of
light output shows good agreemen
Experiments for Double-Beta Decay
The recent neutrino oscillation experimental results indicate that at least
one neutrino has a mass greater than 50 meV. The next generation of double-beta
decay experiments will very likely have a sensitivity to an effective Majorana
neutrino mass below this target. Therefore this is a very exciting time for
this field of research as even null results from these experiments have the
potential to elucidate the nature of the neutrino.Comment: 15 pages, Invited Talk: "Neutrino and Implications for Physics beyond
the Standard Model", Repaired reference in V2, added ref in V
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