arXiv subjects

F. A. Danevich

Publications and source records attributed to F. A. Danevich.

At least 127 records · Page 7Linked to original sources

arXiv2012

Searches for neutrinoless resonant double electron captures at LNGS

Several experiments were performed during last years at underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (LNGS) of the INFN (Italy) to search for resonant 2$\varepsilon0ν$ captures in 96Ru, 106Cd, 136Ce, 156Dy, 158Dy, 180W, 184Os, 190Pt with the help of HP Ge semiconductor detectors, and ZnWO4 and 106CdWO4 crystal scintillators. No evidence for r-2$\varepsilon0ν$ decays was found, and only T_{1/2} limits were established in the range of 10^{14}-10^{21} yr.

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arXiv2011

Experimental research of double beta decay of atomic nuclei

Results of several double beta decay experiments, performed with the help of low background crystal scintillators, are presented. In particular, the half-life value of the two-neutrino double beta decay of 116-Cd has been measured as 2.9 10^{19} yr, and the new half-life limit on the neutrinoless double beta decay of 116-Cd has been established as >1.7 10^{23} yr at 90%, which corresponds to a restriction on the neutrino mass <1.7 eV. New half-life bounds on the level of 10^{17}-10^{21} yr were set for double beta processes in 64-Zn, 70-Zn, 106-Cd, 108-Cd, 114-Cd, 136-Ce, 138-Ce, 142-Ce, 160-Gd, 180-W, and 186-W by using low-background CdWO4, GSO, and ZnWO4 crystal scintillators. The claim of discovery of the neutrinoless double beta decay of 76-Ge [Mod. Phys. Lett. A 16 (2001) 2409] was analyzed. The demands of the future high sensitivity double beta decay experiments, aiming to observe the neutrinoless double beta decay or to advance restrictions on the neutrino mass to < 0.01 eV, were considered. Requirements for their sensitivity and discovery potential were formulated. Two projects of double beta experiments with a sensitivity on the level of 10^{26}-10^{27} yr (CAMEO and CARVEL projects) were discussed. Scintillation properties and radioactive contamination of CaWO4, ZnWO4, CdWO4, PbWO4, GSO(Ce), CeF3, yttrium-aluminum garnet doped with neodymium (YAG:Nd) crystal scintillators were studied. Applicability of these scintillators to search for double beta decay was discussed.

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arXiv2011

Radioactive contamination of SrI2(Eu) crystal scintillator

A strontium iodide crystal doped by europium (SrI2(Eu)) was produced by using the Stockbarger growth technique. The crystal was subjected to a characterization that includes relative photoelectron output and energy resolution for gamma quanta. The intrinsic radioactivity of the SrI2(Eu) crystal scintillator was tested both by using it as scintillator at sea level and by ultra-low background HPGe gamma spectrometry deep underground. The response of the SrI2(Eu) detector to alpha particles (alpha/beta ratio and pulse shape) was estimated by analysing the 226Ra internal trace contamination of the crystal. We have measured: alpha/beta=0.55 at E_alpha=7.7 MeV, and no difference in the time decay of the scintillation pulses induced by alpha particles and gamma quanta. The application of the obtained results in the search for the double electron capture and electron capture with positron emission in 84Sr has been investigated at a level of sensitivity: T_1/2 \sim 10^{15}-10^{16} yr. The results of these studies demonstrate the potentiality of this material for a variety of scintillation applications, including low-level counting experiments.

physics.ins-det↗

arXiv2011

Potential of a next generation neutrinoless double beta decay experiment based on ZnMoO4 scintillating bolometers

The search for neutrinoless double beta decay probes lepton number conservation with high sensitivity and investigates the neutrino nature and mass scale. Experiments presently in preparation will cover the quasi-degeneracy region of the neutrino mass pattern. Probing the so-called inverted hierarchy region requires improved sensitivities and next-generation experiments, based either on large expansions of the present searches or on new ideas. We examine here the potential of a novel technology relying on ZnMoO4 scintillating bolometers, which can provide an experiment with background close to zero in the ton x year exposure scale. The promising performance of a pilot detector is presented, both in terms of energy resolution and background control. A preliminary study of the sensitivities of future experiments shows that the inverted hierarchy region is within the reach of the technique here proposed. A realistic phased approach program towards a next-generation search is presented and briefly discussed.

hep-ex↗

arXiv2011

Final results of an experiment to search for 2beta processes in zinc and tungsten with the help of radiopure ZnWO4 crystal scintillators

A search for the double beta decay of zinc and tungsten isotopes has been performed with the help of radiopure ZnWO4 crystal scintillators (0.1-0.7 kg) at the Gran Sasso National Laboratories of the INFN. The total exposure of the low background measurements is 0.529 kg yr. New improved half-life limits on the double beta decay modes of 64Zn, 70Zn, 180W, and 186W have been established at the level of 10^{18}-10^{21} yr. In particular, limits on double electron capture and electron capture with positron emission in 64Zn have been set: T_{1/2}(2ν2K) > 1.1 10^{19} yr, T_{1/2} (0ν2ε) > 3.2 10^{20} yr, T_{1/2} (2νεβ^+) > 9.4 10^{20} yr, and T_{1/2} (0νεβ^+) > 8.5 10^{20} yr, all at 90% C.L. Resonant neutrinoless double electron capture in 180W has been restricted on the level of T_{1/2} (0ν2ε) > 1.3 10^{18} yr. A new half-life limit on alpha transition of 183W to the metastable excited level 1/2^- 375 keV of 179Hf has been established: T_{1/2} > 6.7 10^{20} yr.

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arXiv2011

Low background detector with enriched 116CdWO4 crystal scintillators to search for double beta decay of 116Cd

A cadmium tungstate crystal boule enriched in $^{116}$Cd to 82% with mass of 1868 g was grown by the low-thermal-gradient Czochralski technique. The isotopic composition of cadmium and the trace contamination of the crystal were estimated by High Resolution Inductively Coupled Plasma Mass-Spectrometry. The crystal scintillators produced from the boule were subjected to characterization that included measurements of transmittance and energy resolution. A low background scintillation detector with two $^{116}$CdWO$_4$ crystal scintillators (586 g and 589 g) was developed. The detector was running over 1727 h deep underground at the Gran Sasso National Laboratories of the INFN (Italy), which allowed to estimate the radioactive contamination of the enriched crystal scintillators. The radiopurity of a third $^{116}$CdWO$_4$ sample (326 g) was tested with the help of ultra-low background high purity germanium $γ$ detector. Monte Carlo simulations of double $β$ processes in $^{116}$Cd were used to estimate the sensitivity of an experiment to search for double $β$ decay of $^{116}$Cd.

physics.ins-det↗

arXiv2011

First search for double beta decay of platinum by ultra-low background HP Ge gamma spectrometry

A search for double beta processes in 190Pt and 198Pt was realized with the help of ultra-low background HP Ge 468 cm^3 gamma spectrometer in the underground Gran Sasso National Laboratories of the INFN (Italy). After 1815 h of data taking with 42.5 g platinum sample, T_{1/2} limits on 2beta processes in 190Pt (εβ^+ and 2ε) have been established on the level of 10^{14}-10^{16} yr, 3 to 4 orders of magnitude higher than those known previously. In particular, a possible resonant double electron capture in 190Pt was restricted on the level of 2.9 \times 10^{16} yr at 90% C.L. In addition, T_{1/2} limit on 2 beta^- decay of 198Pt (2ν+0ν) to the 2^+_1 excited level of 198Hg has been set at the first time: T_{1/2}>3.5 \times 10^{18} yr. The radiopurity level of the used platinum sample is reported.

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arXiv2011

First search for double $β$ decay of dysprosium

A search for double $β$ decay of dysprosium was realized for the first time with the help of an ultra low-background HP Ge $γ$ detector. After 2512 h of data taking with a 322 g sample of dysprosium oxide limits on double beta processes in $^{156}$Dy and $^{158}$Dy have been established on the level of $T_{1/2}\geq 10^{14}-10^{16}$ yr. Possible resonant double electron captures in $^{156}$Dy and $^{158}$Dy were restricted on a similar level. As a by-product of the experiment we have measured the radioactive contamination of the Dy$_2$O$_3$ sample and set limits on the $α$ decay of dysprosium isotopes to the excited levels of daughter nuclei as $T_{1/2}\geq 10^{15} - 10^{17}$ yr.

nucl-ex↗

arXiv2011

First observation of alpha decay of 190-Pt to the first excited level (E_{exc}=137.2 keV) of 186-Os

The alpha decays of naturally occurring platinum isotopes, which are accompanied by the emission of gamma quanta, have been searched for deep underground (3600 m w.e.) in the Gran Sasso National Laboratories of the INFN (Italy). A sample of Pt with mass of 42.5 g and a natural isotopic composition has been measured with a low background HP Ge detector (468 cm^3) during 1815 h. The alpha decay of 190-Pt to the first excited level of 186-Os (J^π= 2^+, E_{exc}=137.2 keV) has been observed for the first time, with the half-life determined as: T_{1/2} = 2.6_{-0.3}^{+0.4} (stat.) \pm 0.6 (syst.) \times 10^{14} yr. The T_{1/2} limits for the alpha decays of other Pt isotopes have been determined at level of T_{1/2} \simeq 10^{16}-10^{20} yr. These limits have been set for the first time or they are better than those known from earlier experiments.

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arXiv2010

Performance of ZnMoO4 crystal as cryogenic scintillating bolometer to search for double beta decay of molybdenum

Zinc molybdate (ZnMoO4) single crystals were grown for the first time by the Czochralski method and their luminescence was measured under X ray excitation in the temperature range 85-400 K. Properties of ZnMoO4 crystal as cryogenic low temperature scintillator were checked for the first time. Radioactive contamination of the ZnMoO4 crystal was estimated as <0.3 mBq/kg (228-Th) and 8 mBq/kg (226-Ra). Thanks to the simultaneous measurement of the scintillation light and the phonon signal, the alpha particles can be discriminated from the gamma/beta interactions, making this compound extremely promising for the search of neutrinoless Double Beta Decay of 100-Mo. We also report on the ability to discriminate the alpha-induced background without the light measurement, thanks to a different shape of the thermal signal that characterizes gamma/beta and alpha particle interactions.

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arXiv2010

Radioactive contamination of ZnWO4 crystal scintillators

The radioactive contamination of ZnWO4 crystal scintillators has been measured deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN in Italy with a total exposure 3197 kg x h. Monte Carlo simulation, time-amplitude and pulse-shape analyses of the data have been applied to estimate the radioactive contamination of the ZnWO4 samples. One of the ZnWO4 crystals has also been tested by ultra-low background gamma spectrometry. The radioactive contaminations of the ZnWO4 samples do not exceed 0.002 -- 0.8 mBq/kg (depending on the radionuclide), the total alpha activity is in the range: 0.2 - 2 mBq/kg. Particular radioactivity, beta active 65Zn and alpha active 180W, has been detected. The effect of the re-crystallization on the radiopurity of the ZnWO4 crystal has been studied. The radioactive contamination of samples of the ceramic details of the set-ups used in the crystals growth has been checked by low background gamma spectrometry. A project scheme on further improvement of the radiopurity level of the ZnWO4 crystal scintillators is briefly addressed.

nucl-ex↗

arXiv2009

Heat flow of the Earth and resonant capture of solar 57-Fe axions

In a very conservative approach, supposing that total heat flow of the Earth is exclusively due to resonant capture inside the Earth of axions, emitted by 57-Fe nuclei on Sun, we obtain limit on mass of hadronic axion: m_a<1.8 keV. Taking into account release of heat from decays of 40-K, 232-Th, 238-U inside the Earth, this estimation could be improved to the value: m_a<1.6 keV. Both the values are less restrictive than limits set in devoted experiments to search for 57-Fe axions (m_a<216-745 eV), but are much better than limits obtained in experiments with 83-Kr (m_a<5.5 keV) and 7-Li (m_a<13.9-32 keV).

nucl-ex↗

arXiv2009

Proceedings of the 1st International Workshop "Radiopure Scintillators for EURECA" (RPScint'2008)

Workshop RPSCINT'2008 was organized in Kyiv (Ukraine) on 9th and 10th September 2008. The idea was to bring together physicists, chemists, crystal scintillator experts and manufacturers to discuss the requirements of low-count rate experiments, in particular the required radiopurity and scintillation properties; selection and screening of input materials; purification of materials; raw compound preparation; crystal growing, annealing and handling; test of crystals; search for and development of new scintillating materials. Some contributions to the RPSCINT 2008 workshop are presented in these proceedings.

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arXiv2008

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.

nucl-ex↗

arXiv2007

Development of CaMoO4 crystal scintillators for double beta decay experiment with 100-Mo

Energy resolution, alpha/beta ratio, pulse-shape discrimination for gamma rays and alpha particles, temperature dependence of scintillation properties, and radioactive contamination were studied with CaMoO4 crystal scintillators. A high sensitivity experiment to search for neutrinoless double beta decay of 100-Mo by using CaMoO4 scintillators is discussed.

nucl-ex↗

arXiv2007

Pulse-shape discrimination with PbWO$_4$ crystal scintillators

The light output, $α/β$ ratio, and pulse shape have been investigated at $-25^\circ$ C with PbWO$_4$ crystal scintillators undoped, and doped by F, Eu, Mo, Gd and S. The fast $0.01-0.06 μ$s and middle $0.1-0.5 μ$s components of scintillation decay were observed for all the samples. Slow components of scintillation signal with the decay times $1-3 μ$s and $13-28 μ$s with the total intensity up to $\approx50%$ have been recognized for several samples doped by Molybdenum. We found some indications of a pulse-shape discrimination between $α$ particles and $γ$ quanta with PbWO$_4$ (Mo doped) crystal scintillators.

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arXiv2006

Further study of CdWO4 crystal scintillators as detectors for high sensitivity double beta experiments: scintillation properties and pulse-shape discrimination

Energy resolution, light yield, non-proportionality in the scintillation response, alpha/beta ratio, pulse shape for gamma rays and alpha particles were studied with CdWO4 crystal scintillators. Some indication for a difference in the emission spectra for gamma rays and alpha particles was observed. No dependence of CdWO4 pulse shape on emission spectrum wavelengths under laser, alpha particles and gamma ray excitation was observed. Dependence of scintillation pulse shape for gamma quanta and alpha particles and pulse-shape discrimination ability on temperature was measured in the range of 0-24 degrees.

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arXiv2004

Application of PbWO4 crystal scintillators in experiment to search for double beta decay of 116Cd

PbWO4 crystal scintillators are discussed as an active shield and light-guides in 116Cd double beta decay experiment with CdWO4 scintillators. Scintillation properties and radioactive contamination of PbWO4 scintillators were investigated. Energy resolution of CdWO4 detector, coupled to PbWO4 crystal as a light-guide, was tested. Efficiency of PbWO4-based active shield to suppress background from the internal contamination of PbWO4 crystals was calculated. Using of lead tungstate crystal scintillators as high efficiency 4-pi active shield could allow to build sensitive double beta experiment with 116CdWO4 crystal scintillators.

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