Search

A search for the β+β+, β+/EC, and EC/EC decays of 106Cd was performed at the Modane Underground Laboratory (France) located at a depth of 4800 m w.e. using a TGV-2 multidetector germanium spectrometer. A preliminary evaluation is performed of the experimental data accumulated during the measurements (12 900 h) of ∼13.6 g of 106Cd (with an enrichment of 75%) and the spectrometer background without samples and with samples of natural Cd. New limits (at a 90% confidence level) of half-lives are obtained: T 1/2 ⩾ 1.7 × 1020 yr and T 1/2 ⩾ 1.6 × 1020 yr for the 0νEC/EC resonant decay of 106Cd to the 2741 keV and 2718 keV excited states of the daughter nucleus 106Pd and T 1/2 ⩾ 4.2 × 1020 yr for the 2νEC/EC decay to the ground state of 106Pd (0+ → 0+, g.s.). The limits for other branches of the double beta decay of 106Cd with transitions to the ground and excited states of 106Pd are improved.

The half-life of $^{212}$Po was measured with the highest up-to-date accuracy as $T_{1/2}=295.1(4)$ ns by using thorium-loaded liquid scintillator., Comment: 28 pages, 13 figures, 4 tables

The CUPID-Mo experiment at the Laboratoire Souterrain de Modane (France) is a demonstrator for CUPID, the next-generation ton-scale bolometric 0νββ experiment. It consists of a 4.2 kg array of 20 enriched Li_{2}^{100}MoO_{4} scintillating bolometers to search for the lepton-number-violating process of 0νββ decay in ^{100}Mo. With more than one year of operation (^{100}Mo exposure of 1.17 kg×yr for physics data), no event in the region of interest and, hence, no evidence for 0νββ is observed. We report a new limit on the half-life of 0νββ decay in ^{100}Mo of T_{1/2}>1.5×10^{24} yr at 90% C.I. The limit corresponds to an effective Majorana neutrino mass ⟨m_{ββ}⟩

CUPID-Mo is a cryogenic detector array designed to search for neutrinoless double-beta decay (0νββ) of 100Mo. It uses 20 scintillating 100Mo-enriched Li2MoO4 bolometers instrumented with Ge light detectors to perform active suppression of α backgrounds, drastically reducing the expected background in the 0νββ signal region. As a result, pileup events and small detector instabilities that mimic normal signals become non-negligible potential backgrounds. These types of events can in principle be eliminated based on their signal shapes, which are different from those of regular bolometric pulses. We show that a purely data-driven principal component analysis based approach is able to filter out these anomalous events, without the aid of detector response simulations.

An experiment to measure the 2β – decay of 150Nd to excited levels of 150Sm using a highly purified 2.381 kg sample of Nd2O3 is in progress in the low-background set-up with 4 HPGe detectors (∼225 cm3 volume each). The detector is located deep underground (3600 m w.e.) at the STELLA facility of the Gran Sasso National Laboratory (LNGS) of the INFN (Italy). Two γ quanta with energies 334.0 keV and 406.5 keV emitted after deexcitation of the 01 + excited level of 150Sm have been observed in the experimental data accumulated over 39898 h. The preliminary half-life value for 2β – decay of 150Nd to the first 0+ excited level in 150Sm (after the exposure of 10.8 kg × yr) was estimated as T 1 / 2 = 9.7 − 1.9 + 2.9 stat . ± 1.5 syst . × 10 19 yr. The experiment is under data taking with the aim to improve the statistical uncertainties.

Studies on double beta decay processes in 106Cd were performed by using a cadmium tungstate scintillator enriched in 106Cd at 66% (106CdWO4) with two CdWO4 scintillation counters (with natural Cd composition). No effect was observed in the data that accumulated over 26,033 h. New improved half-life limits were set on the different channels and modes of the 106Cd double beta decay at level of limT1/2&sim, 1020&minus, 1022 yr. The limit for the two neutrino electron capture with positron emission in 106Cd to the ground state of 106Pd, T1/22&nu, EC&beta, +&ge, 2.1&times, 1021 yr, was set by the analysis of the 106CdWO4 data in coincidence with the energy release 511 keV in both CdWO4 counters. The sensitivity approaches the theoretical predictions for the decay half-life that are in the range T1/2&sim, 1021&minus, 1022 yr. The resonant neutrinoless double-electron capture to the 2718 keV excited state of 106Pd is restricted at the level of T1/20&nu, 2K&ge, 2.9&times, 1021 yr.

A search for $\ensuremath{\alpha}$ decay of naturally occurring osmium isotopes to the lowest excited levels of daughter nuclei has been performed by using an ultra-low-background broad-energy germanium $\ensuremath{\gamma}$ detector with a volume of 112 ${\mathrm{cm}}^{3}$ and an ultrapure osmium sample with a mass of 118 g at the Gran Sasso National Laboratory of the INFN (Italy). The isotopic composition of the osmium sample has been measured with high precision using negative thermal ionization mass spectrometry. After 15851 h of data taking with the $\ensuremath{\gamma}$ detector, no effect has been detected, and lower limits on the $\ensuremath{\alpha}$ decays were set at level of $lim{T}_{1/2}\ensuremath{\approx}{10}^{15}--{10}^{19}$ yr. The limits for the $\ensuremath{\alpha}$ decays of $^{184}\mathrm{Os}$ and $^{186}\mathrm{Os}$ to the first excited levels of daughter nuclei, ${T}_{1/2}(^{184}\mathrm{Os})\ensuremath{\ge}6.8\ifmmode\times\else\texttimes\fi{}{10}^{15}$ yr and ${T}_{1/2}(^{186}\mathrm{Os})\ensuremath{\ge}3.3\ifmmode\times\else\texttimes\fi{}{10}^{17}$ yr (at 90% C.L.), exceed the present theoretical estimates of the decays' half-lives. For $^{189}\mathrm{Os}$ and $^{192}\mathrm{Os}$ also decays to the ground states of the daughter nuclei were searched for due to the instability of the daughter nuclides relative to $\ensuremath{\beta}$ decay.

International audience; Many developments, researches on innovative materials and purification techniques have offered a wide set of inorganic scintillators to investigate many processes; further developments are still in progress. In particular, efforts to realize very low background detectors have opened their effective application to the search of rare processes deep underground. Several cases will be outlined offering—to some extent—a discussion of several inorganic crystal scintillators' performances and their potentiality for the future.

Precise measurement of half-life of $^{212}$Po (one of the daughter nuclides in radioactive chain of $^{232}$Th) was realized by means of liquid scintillator based on toluene doped by complex of thorium and trioctylphosphine oxide with concentration of Th $\sim0.1$ mass %. Fast photomultiplier tube and high frequency oscilloscope were used to acquire the scintillation signals waveforms. The algorithms were developed to find pairs of $^{212}$Bi beta-decays and subsequent $^{212}$Po alpha-decays, to calculate time differences between the events in the pair, and to build $^{212}$Bi beta-decay and $^{212}$Po alpha-decay energy spectra. Preliminary the $^{212}$Po half-life is $T_{1/2} = (294.8 \pm 1.9)$ ns. The experiment is in progress aiming at reduction of the statistical and systematic uncertainties., 7 pages, in Ukrainian, 7 figures

The double beta decay of 150Nd to the first excited 0+ level of 150Sm (Eexc = 740.5 keV) was investigated with the help of the ultra-low-background setup consisting of four HP Ge (high-purity germanium) detectors (≃225 cm3 volume each one) at the Gran Sasso underground laboratory of INFN (Italy). A highly purified 2.381-kg sample of neodymium oxide (Nd2O3) was used as a source of γ quanta expected in the decays. Gamma quanta with energies 334.0 keV and 406.5 keV emitted after deexcitation of the 01+ 740.5 keV excited level of 150Sm are observed in the coincidence spectra accumulated over 16375 h. The half-life relatively to the two neutrino double beta decay 150Nd → 150Sm(01+) is measured as T1/2 = [4.7+4.1-1.9(stat)±0.5(syst)]×1019 y, in agreement with results of previous experiments.

International audience; Cadmium-116 is one of the favorable candidates for neutrinoless double-beta decay ($0\nu \beta \beta $) searches from both theoretical and experimental points of view, in particular thanks to the high energy of the decay (2813.49 keV), the possibility of the industrial enrichment in $^{116}\mathrm{Cd}$ and its use in the well-established production of cadmium tungstate crystal scintillators. In this work, we present low-temperature tests of two $0.6\ \mathrm{kg} \ ^{116}\hbox {CdWO}_{{4}}$ crystals enriched in $^{116}\mathrm{Cd}$ to $82\%$ as scintillating bolometers. These detectors were operated underground, with one at the Laboratoire Souterrain de Modane (LSM) in France and the second at the Laboratorio Subterraneo de Canfranc (LSC) in Spain. The two crystals are coupled to bolometric Ge light detectors in order to register the scintillation light. The double readout of heat and scintillation enables reduction in the background in the region of interest by discriminating between different populations of particles. The main goal of these tests is the study of the crystals’ radiopurity and the detectors’ performance. The achieved results are extremely promising, in particular, the detectors demonstrate a high energy resolution (11–16 keV FWHM at 2615 keV) and a high-efficiency discrimination of the alpha background ($\sim 20 \sigma $). These results, achieved for the first time with large mass enriched $^{116}\hbox {CdWO}_{{4}}$ crystals, demonstrate prospects of the bolometric technology for high-sensitivity searches of $^{116}\mathrm{Cd}0\nu \beta \beta $ decay.

International audience; Final results of studies of 116Cd 2β decay with CdWO4 crystal scintillators, enriched in 116Cd to 82%, are presented. After few years (2011 – 2017) of measurements with radiopure 116CdWO4 scintillators (mass of 1.162 kg) at the Gran Sasso underground laboratory (Italy), the half-life of 116Cd relatively to 2ν2β decay to the ground state of 116Sn was measured with the highest up-to-date accuracy as T1/2=(2.63−0.12+0.11)×1019 yr. A new limit on 0ν2β decay of 116Cd was set as T1/2≥2.2×1023 yr at 90% C.L., which is the most stringent to-date restriction for this isotope. Limits for 0ν2β decay with majoron(s) emission, Lorentz-violating 2ν2β decay and 2β transitions to excited states of 116Sn were set at the level of T1/2≥1020−1022 yr.

International audience; The half-life of 100Mo relatively to the 2ν2β decay to the ground state of 100Ru was measured as T1/2 = (6.99±0.15) × 1018 yr with the help of enriched in 100Mo lithium molybdate scintillating bolometers in the EDELWEISS-III low background set-up at the Modane underground laboratory. This is the most accurate value of the 2ν2β half-life of 100Mo.

Two-neutrino 2β decay of 150Nd to the 01+ 740.5-keV excited level of 150Sm has been investigated by using a highly purified 2.381-kg Nd2O3 sample with the help of ultra-low-background gamma spectrometer with 4 HPGe detectors (≈ 255 cm3 each) at the Gran Sasso underground laboratory (INFN, Italy). Gamma quanta, expected in cascade after de-excitation of the 01+ (740.5 keV) excited level of 150Sm, have been observed in the coincidence spectra accumulated over 25947 h. The half-life value has been preliminary estimated as T1/2=[ 6.9−1.9+4.0(stat)±1.1(syst) ]×109y. The data taking is in progress to reduce the statistical error.Two-neutrino 2β decay of 150Nd to the 01+ 740.5-keV excited level of 150Sm has been investigated by using a highly purified 2.381-kg Nd2O3 sample with the help of ultra-low-background gamma spectrometer with 4 HPGe detectors (≈ 255 cm3 each) at the Gran Sasso underground laboratory (INFN, Italy). Gamma quanta, expected in cascade after de-excitation of the 01+ (740.5 keV) excited level of 150Sm, have been observed in the coincidence spectra accumulated over 25947 h. The half-life value has been preliminary estimated as T1/2=[ 6.9−1.9+4.0(stat)±1.1(syst) ]×109y. The data taking is in progress to reduce the statistical error.

An experiment to search for double beta processes in 106Cd is in progress with the help of 106CdWO4 crystal scintillator (enriched in 106Cd to 66%) in coincidence with two large volume CdWO4 crystal scintillators in close geometry at the Gran Sasso Underground Laboratory. The time resolution of the set-up was analyzed, and the methods of pulse-shape discrimination of α and γ(β) events was applied to estimate the radioactive contamination of the crystal and to reduce the background counting rate. The possible double beta decay processes and the background components have been simulated by a Monte Carlo method with GEANT4. The experimental sensitivity is approaching the theoretical predictions for the two-neutrino electron capture with positron emission in 106Cd: lim T1/2≥4×1021 yr at 90% C.L. (the best previous limit was established in the previous stage of the experiment as T1/2≥1.1× 1021 yr, while the theoretical predictions are in the region of T1/2∼1021−1022 yr).An experiment to search for double beta processes in 106Cd is in progress with the help of 106CdWO4 crystal scintillator (enriched in 106Cd to 66%) in coincidence with two large volume CdWO4 crystal scintillators in close geometry at the Gran Sasso Underground Laboratory. The time resolution of the set-up was analyzed, and the methods of pulse-shape discrimination of α and γ(β) events was applied to estimate the radioactive contamination of the crystal and to reduce the background counting rate. The possible double beta decay processes and the background components have been simulated by a Monte Carlo method with GEANT4. The experimental sensitivity is approaching the theoretical predictions for the two-neutrino electron capture with positron emission in 106Cd: lim T1/2≥4×1021 yr at 90% C.L. (the best previous limit was established in the previous stage of the experiment as T1/2≥1.1× 1021 yr, while the theoretical predictions are in the region of T1/2∼1021−1022 yr).

The double-beta decay of Cd116 has been investigated with the help of radiopure enriched Cd116WO4 crystal scintillators (mass of 1.162 kg) at the Gran Sasso underground laboratory. The half-life of Cd116 relative to the 2ν2β decay to the ground state of Sn116 was measured with the highest up-to-date accuracy as T1/2=(2.63-0.12+0.11)×1019 yr. A new improved limit on the 0ν2β decay of Cd116 to the ground state of Sn116 was set as T1/2≥2.2×1023 yr at 90% C.L., which is the most stringent known restriction for this isotope. It corresponds to the effective Majorana neutrino mass limit in the range ⟨mν⟩≤(1.0–1.7) eV, depending on the nuclear matrix elements used in the estimations. New improved half-life limits for the 0ν2β decay with majoron(s) emission, Lorentz-violating 2ν2β decay, and 2β transitions to excited states of Sn116 were set at the level of T1/2≥1020–1022 yr. New limits for the hypothetical lepton-number violating parameters (right-handed currents admixtures in weak interaction, the effective majoron-neutrino coupling constants, R-parity violating parameter, Lorentz-violating parameter, heavy neutrino mass) were set.

Double beta decay of $^{116}$Cd has been investigated with the help of radiopure enriched $^{116}$CdWO$_4$ crystal scintillators in the experiment Aurora. The half-life of $^{116}$Cd relatively to the 2$\nu$2$\beta$ decay of $^{116}$Cd to the ground level of $^{116}$Sn is measured with the highest up-to-date accuracy as $T_{1/2}$ = [2.69 $\pm$ 0.02 (stat.) $\pm$ 0.14 (syst.)] $\times$ 10$^{19}$ yr. A new improved limit on the 0$\nu$2$\beta$ decay of $^{116}$Cd to the ground state of $^{116}$Sn is set as $T_{1/2}\geq 2.4 \times 10^{23}$ yr at 90\% C.L., that corresponds to the effective Majorana neutrino mass limit in the range $\langle$$m_\nu$$\rangle$ $\le$ $(1.1-1.6)$ eV, depending on the nuclear matrix elements used in the estimations. New improved limits on other $2\beta$ processes in $^{116}$Cd (decays with majoron emission, transitions to excited levels of $^{116}$Sn) were set at the level of $T_{1/2}\geq 10^{21}-10^{22}$ yr., Comment: 4 pages, 2 figures

An experiment to search for double beta decay in 106Cd is running in the DAMA/CRYS set-up at the Gran Sasso National Laboratory of the INFN (Italy). In this experiment a 106CdWO4 crystal scintillator (215 g) enriched in 106Cd to 66%, used in previous measurements in different configurations, is now in measurement in coincidence with two large volume low background CdWO4 crystal scintillators in close geometry. This further measurement will allow us to reach a sensitivity at the level of the most sensitive double β+ experiments (T1/2 ≃ 1020 −1022 yr) and to explore the region of the theoretical expectations for some decay modes.An experiment to search for double beta decay in 106Cd is running in the DAMA/CRYS set-up at the Gran Sasso National Laboratory of the INFN (Italy). In this experiment a 106CdWO4 crystal scintillator (215 g) enriched in 106Cd to 66%, used in previous measurements in different configurations, is now in measurement in coincidence with two large volume low background CdWO4 crystal scintillators in close geometry. This further measurement will allow us to reach a sensitivity at the level of the most sensitive double β+ experiments (T1/2 ≃ 1020 −1022 yr) and to explore the region of the theoretical expectations for some decay modes.

A sample of 100MoO3 powder with molybdenum enriched in 100Mo to 99.5% and mass of 1199 g was measured for 18120 h in a low-background set-up with 4 HP Ge detectors ( ≃ 225 cm 3 volume each one) deep underground (3600 m w.e.) at the Laboratori Nazionali del Gran Sasso of the INFN (Italy). The two γ quanta of 540 keV and of 591 keV emitted in the deexcitation process after a 2 β 2 ν decay of 100Mo to the 0 1 + excited level of 100Ru ( E exc = 1131 keV ) are observed in the accumulated data both in coincidence and in the 1-dimensional sum spectrum. The measured half life is: T 1 / 2 = 6.9 − 0.8 + 1.0 ( stat. ) ± 0.7 ( syst. ) × 10 20 yr , well in agreement with positive results obtained in previous experiments. Moreover, the limit on charge non-conserving β decay of 100Mo is also set: τ CNC > 4.5 × 10 19 yr at 90% C.L.; it corresponds to the limit on CNC admixture in weak currents: ϵ ν 2 2.9 × 10 − 21 .

Search for neutrino-less double beta decay of 100Mo is proposed using active method with Ca 100MoO4 scintillation crystals which show the brightest scintillation light among variety of inorganic scintillation materials containing Mo. Study of X-ray luminescence and scintillation properties such as energy response, number of photoelectrons/keV, absolute light yield, decay time, pulse shape discrimination and radioactive contamination of CaMoO4 crystals grown by the Czochralski method with different conditions are presented. Further R&D of resolution optimization, crystal quality improvement and background reduction are underway. Significant improvement of sensitivity to neutrino-less double beta decay can be achieved by using 10 Mo enriched Ca 100MoO4 crystals with good energy resolution and low background. Further reduction of background induced by 48 Ca two neutrino double beta decay can be achieved by using 48Ca depletion. We are planning to install several kilograms of Ca 100MoO4 crystals depleted in 48Ca at underground laboratory for the neutrino-less double beta decay experiment in the near future.

A cadmium tungstate crystal scintillator enriched in 106 Cd was developed for an experiment to search for double beta processes in 106 Cd. With this aim samples of cadmium with natural isotopic composition and enriched in 106 Cd were purified by vacuum distillation. Cadmium tungstate compounds were synthesized from solutions. The absolute isotopic composition of the enriched cadmium was accurately determined as 66.4% by thermal ionisation mass-spectrometry. A 106 CdWO 4 crystal boule was grown by the low-thermal-gradient Czochralski technique. The total irrecoverable loss of the enriched cadmium in all the stages of the crystal scintillator production does not exceed 2.3%. The produced 106 CdWO 4 crystal scintillator with mass of 216 g exhibits good optical and scintillation properties.

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, 8 pages

We have studied the energy resolution, α / β ratio, temperature dependence of the scintillation properties, and the radioactive contamination of CaMoO4 crystal scintillators. We have also examined the use of pulse-shape discrimination to distinguish γ rays and α particles. A high sensitivity experiment to search for the 0 ν 2 β decay of Mo 100 using CaMoO4 scintillators is discussed.

A small Li 6 Eu ( BO 3 ) 3 crystal (2.72 g) was measured deep underground at the Gran Sasso National Laboratories with a HP Ge detector of 408 cm 3 during 1500 h. While the crystal is not polluted by usual radioactive contaminants (only limits on the activity of U/Th chains, 40 K, 60 Co, 137 Cs were set on the level of 0.01–1 Bq/kg), the presence of radioactive 152 Eu and 154 Eu is evident; these are created in capture of neutrons by naturally abundant 151 Eu and 153 Eu. The measured activities correspond to 0.95 and 0.21 Bq/kg for 152 Eu and 154 Eu, respectively, with a ratio far from the standard expectation. As by-products, limits on half lives for the α decays Eu 151 → Pm 147 ( E exc = 91.1 keV ) and Eu 153 → Pm 149 are determined as T 1 / 2 > 2.4 × 10 16 yr and T 1 / 2 > 1.1 × 10 16 yr , respectively.

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}(2\nu 2K) > 1.1 10^{19} yr, T_{1/2} (0\nu 2\epsilon) > 3.2 10^{20} yr, T_{1/2} (2\nu \epsilon \beta^+) > 9.4 10^{20} yr, and T_{1/2} (0\nu \epsilon \beta^+) > 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} (0\nu 2\epsilon) > 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., Comment: This is an author-created, un-copyedited version of an article published in J. Phys. G: Nucl. Part. Phys. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at doi: 10.1088/0954-3899/38/11/115107

Some recent results obtained in the search for double beta decay in vari- ous isotopes obtained in experiments carried out at LNGS with the DAMA/R&D, DAMA/Ge set-up and the STELLA facility will be summarized.

ISBN: 978-0-7354-1333-7; International audience; The LUMINEU program aims at performing a pilot experiment on 0ν2β decay of 100 Mo using radiopure ZnMoO4 crystals enriched in 100 Mo operated as cryogenic scintillating bolometers. Large volume ZnMoO4 crystal scintillators (∼ 0.3 kg) were developed and tested showing high performance in terms of radiopurity, energy resolution and α/β particle discrimination capability. Zinc molybdate crystal scintillators enriched in 100 Mo were grown for the first time by the low-thermal-gradient Czochralski technique with a high crystal yield and an acceptable level of enriched molybdenum irrecoverable losses. A background level of ∼ 0.5 counts/(yr keV ton) in the region of interest can be reached in a large detector array thanks to the excellent detectors radiopurity and particle discrimination capability, suppression of randomly coinciding events by pulse-shape analysis, and anticoincidence cut. These results pave the way to future sensitive searches based on the LUMINEU technology, capable of approaching and exploring the inverted hierarchy region of the neutrino mass pattern.

An experiment to search for 2β processes in 116Cd with the help of enriched (to 82%) cadmium tungstate crystal scintillators is in progress at the Gran Sasso National Laboratory of the INFN (LNGS, Italy). After 11074 h of data taking in the last configuration, the preliminary estimate for the half-life of 116Cd relatively to 2ν2β decay is T1/2 = [2.52 ± 0.02(stat.) ± 0.14(syst.)] × 1019 yr. By using the data of previous stages of the experiment with a similar level of background (≈ 0.1 counts/(keV kg yr) in the energy interval 2.7 – 2.9 MeV; the total time of measurements is 19770 h) we have obtained a new limit on the 0ν2β decay of 116Cd to the ground state of 116Sn: T1/2 ≥ 1.9 × 1023 yr at 90% C.L. New limits on different 2β processes in 116Cd (decays with majorons, transitions to the excited levels) are obtained on the level of T1/2 ≥ 1020 – 1022 yr.

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., Comment: 22 pages, 14 figures, submitted to NIMA

Energy resolution, α / β ratio, pulse-shape discrimination for γ -rays and α particles and radioactive contamination were studied with yttrium–aluminum garnet doped with neodymium (YAG:Nd). Applicability of YAG:Nd scintillators to search for 2 β decay and α activity of natural neodymium isotopes is discussed.

The CARVEL (CAlcium Research for VEry Low neutrino mass) experiment to search for the double β decay of 48 Ca with the help of enriched 48 CaWO 4 crystal scintillators has been considered. Scintillation properties (energy resolution, α/β ratio, pulse-shape discrimination ability) and radiopurity of CaWO 4 scintillators were studied. Despite rather high radioactive contaminations, the background rate of the CaWO 4 detector in the energy region 3.6–5.4 MeV (energy window of the 48 Ca neutrinoless 2β decay) was reduced down to 0.07 counts/(yr keV kg). With ≈100 kg array of the 48 CaWO 4 crystals the sensitivity of the CARVEL experiment (in terms of the half-life limit for the 0ν2β decay) is estimated as T 1 / 2 0 ν > 10 27 yr. This value corresponds to the neutrino mass constraint m ν

Final results of the 2 β decay experiment, performed in the Solotvina Underground Laboratory with the help of low-background 116 CdWO 4 crystal scintillators, are presented. The revised half-life value of the two-neutrino 2 β decay of 116 Cd has been measured as T 1 / 2 2 ν = 2.9 −0.3 +0.4 × 10 19 yr, and the new half-life limit on the neutrinoless 2 β decay of 116 Cd has been established as T 1 / 2 0 ν ⩾ 1.7 (2.6)×10 23 yr at 90% (68%) C.L. The latter corresponds to a restriction on the Majorana neutrino mass: m ν ⩽ 1.7 (1.4) eV at 90% (68%) C.L. The CAMEO project could further advance sensitivity of the 116 Cd experiment to m ν ⩽ 0.05 eV.

Cadmium tungstate crystal scintillators enriched in 106Cd up to 66% (106CdWO4) and in 116Cd up to 82% (116CdWO4) have been developed. The low radioactive contamination of the crystals measured on the level of ≤ 1.5 mBq/kg (40K), ≤ 0.005 - 0.012 mBq/kg (226Ra), 0.04 - 0.07 mBq/kg (228Th) allows to carry out high sensitivity experiments to search for double beta processes in 106Cd and 116Cd.

The Aurora experiment to investigate double beta decay of $^{116}$Cd with the help of 1.162 kg cadmium tungstate crystal scintillators enriched in $^{116}$Cd to 82\% is in progress at the Gran Sasso Underground Laboratory. The half-life of $^{116}$Cd relatively to the two neutrino double beta decay is measured with the highest up-to-date accuracy $T_{1/2}=(2.62\pm0.14)\times10^{19}$ yr. The sensitivity of the experiment to the neutrinoless double beta decay of $^{116}$Cd to the ground state of $^{116}$Sn is estimated as $T_{1/2} \geq 1.9\times10^{23}$ yr at 90\% CL, which corresponds to the effective Majorana neutrino mass limit $\langle m_{\nu}\rangle \leq (1.2-1.8)$ eV. New limits are obtained for the double beta decay of $^{116}$Cd to the excited levels of $^{116}$Sn, and for the neutrinoless double beta decay with emission of majorons., Comment: 5 pages, 3 figures, 1 table, submitted as proceedings of the TAUP 2015 conference

Cadmium tungstate crystal scintillators enriched in 106Cd (106CdWO 4 ) and 116Cd (116CdWO 4 ) have been developed to search for 2β-decay of 106Cd and 116Cd.

A search for double $\ensuremath{\beta}$ processes in ${}^{106}$Cd was carried out at the Gran Sasso National Laboratories of the INFN (Italy) with the help of a ${}^{106}$CdWO${}_{4}$ crystal scintillator (215 g) enriched in ${}^{106}$Cd up to 66$%$. After 6590 h of data taking, new improved half-life limits on the double $\ensuremath{\beta}$ decay processes in ${}^{106}$Cd were established at the level of ${10}^{19}$--${10}^{21}$ yr; in particular, ${T}_{1/2}^{2\ensuremath{\nu}\ensuremath{\varepsilon}{\ensuremath{\beta}}^{+}}\ensuremath{\geqslant}2.1\ifmmode\times\else\texttimes\fi{}{10}^{20}$ yr, ${T}_{1/2}^{2\ensuremath{\nu}2{\ensuremath{\beta}}^{+}}\ensuremath{\geqslant}4.3\ifmmode\times\else\texttimes\fi{}{10}^{20}$ yr, and ${T}_{1/2}^{0\ensuremath{\nu}2\ensuremath{\varepsilon}}\ensuremath{\geqslant}1.0\ifmmode\times\else\texttimes\fi{}{10}^{21}$ yr. The resonant neutrinoless double-electron captures to the 2718-, 2741-, and 2748-keV excited states of ${}^{106}$Pd are restricted to ${T}_{1/2}^{0\ensuremath{\nu}2K}\ensuremath{\geqslant}4.3\ifmmode\times\else\texttimes\fi{}{10}^{20}$ yr, ${T}_{1/2}^{0\ensuremath{\nu}K{L}_{1}}\ensuremath{\geqslant}9.5\ifmmode\times\else\texttimes\fi{}{10}^{20}$ yr, and ${T}_{1/2}^{0\ensuremath{\nu}K{L}_{3}}\ensuremath{\geqslant}4.3\ifmmode\times\else\texttimes\fi{}{10}^{20}$ yr, respectively (all limits at 90$%$ confidence level). A possible resonant enhancement of the $0\ensuremath{\nu}2\ensuremath{\varepsilon}$ processes is estimated in the framework of the quasiparticle random phase approximation (QRPA) approach. Radioactive contamination of the ${}^{106}$CdWO${}_{4}$ crystal scintillator is reported.

The measurements with 0.33 kg low background 116CdWO4 scintillators are in progress in the Solotvina Underground Laboratory. After 13254 h of data taking the new half-life limits for different modes of neutrinoless 2β decay of 116Cd are presented, in particular for 0ν2β decay of 116Cd to the ground state of 116Sn: T1/2;(0ν2β) ≥ 1.3(1.8) × 1023 yr at 90%(68%) C.L.

Borexino, at the I.N.F.N. Gran Sasso Underground Laboratory in Italy, is an experiment designed to detect, in real-time, low energy solar neutrinos. After a brief presentation of the Borexino physics and detector, we illustrate some recent results and their physics implications. Borexino perspectives are also discussed.

beta decay of (113)Cd was studied with the help of a low background CdWO(4) crystal scintillator (mass of 434 g) in an experiment at the Gran Sasso National Laboratories of the INFN for a period of 2758 h. The shape of the spectrum of the non-unique fourth-forbidden decay of (113)Cd was measured, and the half-life of (113)Cd was determined as T(1/2)=(8.04 +/- 0.05)x10(15) yr.

The data collected with a radioactively pure ZnWO$_4$ crystal scintillator (699 g) in low background measurements during 2130 h at the underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (INFN, Italy) were used to set a limit on possible concentration of superheavy eka-W (seaborgium Sg, Z = 106) in the crystal. Assuming that one of the daughters in a chain of decays of the initial Sg nucleus decays with emission of high energy $\alpha$ particle ($Q_\alpha > 8$ MeV) and analyzing the high energy part of the measured $\alpha$ spectrum, the limit N(Sg)/N(W) < 5.5 $\times$ 10$^{-14}$ atoms/atom at 90% C.L. was obtained (for Sg half-life of 10$^9$ yr). In addition, a limit on the concentration of eka-Bi was set by analysing the data collected with a large BGO scintillation bolometer in an experiment performed by another group [L. Cardani et al., JINST 7 (2012) P10022]: N(eka-Bi)/N(Bi) < 1.1 $\times$ 10$^{-13}$ atoms/atom with 90% C.L. Both the limits are comparable with those obtained in recent experiments which instead look for spontaneous fission of superheavy elements or use the accelerator mass spectrometry., Comment: 9 pages, 2 figures; in press on Physica Scripta

Radioactive contaminations of CaWO4, ZnWO4, CdWO4, and Gd2SiO5:Ce crystal scintillators were measured in the Solotvina Underground Laboratory. The Monte Carlo simulation of contributing radioactive sources, the time‐amplitude and pulse‐shape analyses of the experimental data were applied. CaWO4 and GSO scintillators are considerably polluted by uranium and thorium, while the total α activity in ZnWO4 and CdWO4 scintillators does not exceed the level of a few mBq/kg. Particular radioactivity was observed in CaWO4 (α active 180W), CdWO4 (β active 113Cd, 2v2β decay of 116Cd, 180W), and GSO (α active 152Gd) detectors. The radioactive contamination of the studied scintillation crystals is compared with that of commonly used detectors.

The experiment with a large (≈95 cm3) Gd2SiO5:Ce crystal scintillator has been performed in the Solotvina Underground Laboratory to search for neutrinoless double beta decay of 160Gd. The background rate was reduced to a level of 0.045 counts/h/keV/kg in the vicinity of ββ decay energy of 160Gd (1730 keV). The half-life limits have been set for 0vββ decay of 160Gd: T1/2ov(g.s. → g.s.) ≥ 8.2·1020 y (90% CL); T1/2ov (0+ → 2+) ≥ 8.2·1020 y (90% CL).

The experiment was performed at the Solotvina Underground Laboratory with CdWO 4 crystal scintillators enriched in 116 Cd to 83%. For the total data collection time about 12000 hours the limit of half-life T 1/2 ov ≥ 3.2·10 22 y (90% CL) was obtained for 0vββ decay of 116 Cd which corresponds to the restriction of the neutrino mass less than 3.9 eV.

The LUMINEU program aims at performing a pilot experiment on neutrinoless double beta decay of 100Mo using radiopure ZnMoO4 crystals operated as cryogenic scintillating bolometers. Growth of high quality radiopure crystals is a complex task, since there are no commercial molybdenum compounds available with the required level of purity and radioactive contamination. This paper discusses approaches to purify molybdenum and synthesize compounds for high quality radiopure ZnMoO4 crystal growth. A combination of a double sublimation (with addition of zinc molybdate) with subsequent recrystallization in aqueous solutions (using zinc molybdate as a collector) was used. Zinc molybdate crystals up to 1.5 kg were grown by the low-thermal-gradient Czochralski technique; their optical, luminescent, diamagnetic, thermal and bolometric properties were tested.

Cadmium tungstate crystal scintillators enriched in $^{116}$Cd to 82% ($^{116}$CdWO$_4$, total mass of $\approx$1.2 kg) are used to search for 2$\beta$ decay of $^{116}$Cd deep underground at the Gran Sasso National Laboratory of the INFN (Italy). The radioactive contamination of the $^{116}$CdWO$_4$ crystals has been studied carefully to reconstruct the background of the detector. The measured half-life of $^{116}$Cd relatively to 2$\nu$2$\beta$ decay is $T^{2\nu2\beta}_{1/2}$ = [2.8 $\pm$ 0.05(stat.) $\pm$ 0.4(syst.)] $\times$ 10$^{19}$ yr, in agreement with the results of previous experiments. The obtained limit on the 0$\nu$2$\beta$ decay of $^{116}$Cd (considering the data of the last 8696 h run with an advanced background 0.12(2) counts/yr/kg/keV in the energy interval 2.7-2.9 MeV) is $T_{1/2} \ge 1.0 \times 10^{23}$ yr at 90% C.L. The sensitivity of the experiment to the $0\nu2\beta$ process is $\lim T_{1/2} = 3 \times 10^{23}$ yr at 90% C.L. over 5 years of the measurements and it can be advanced (by further reduction of the background by a factor 3-30) to the level of $\lim T_{1/2} = (0.5-1.5) \times 10^{24}$ yr for the same period of the data taking., Comment: Contribution to Proc. of Int. Workshop on Radiopure Scintillators RPSCINT 2013, 17-20.09.2013, Kyiv, Ukraine; to be published in EPJ Web of Conferences; 4 pages, 1 figure and 3 tables

A new phase of a ${}^{116}\mathrm{Cd}$ double \ensuremath{\beta} decay experiment is in progress in the Solotvina Underground Laboratory. Four enriched ${}^{116}{\mathrm{CdWO}}_{4}$ scintillators with total mass of 339 g are used in a setup, whose active shield is made of 15 natural ${\mathrm{CdWO}}_{4}$ crystals (20.6 kg). The background rate in the energy interval 2.5--3.2 MeV is 0.03 counts/yr kg keV. The half-life for 2\ensuremath{\nu}2\ensuremath{\beta} decay of ${}^{116}\mathrm{Cd}$ is measured as ${T}_{1/2}(2\ensuremath{\nu})=2.6\ifmmode\pm\else\textpm\fi{}0.1(\mathrm{stat}{)}_{\ensuremath{-}0.4}^{+0.7}(\mathrm{syst})\ifmmode\times\else\texttimes\fi{}{10}^{19}$ yr. The ${T}_{1/2}$ limits for neutrinoless 2\ensuremath{\beta} decay of ${}^{116}\mathrm{Cd}$ are set at ${T}_{1/2}g~0.7(2.5)\ifmmode\times\else\texttimes\fi{}{10}^{23}$ yr at 90%(68%) C.L. for transition to ground state of ${}^{116}\mathrm{Sn},$ while for decays to the first ${2}_{1}^{+}$ and second ${0}_{1}^{+}$ excited levels of ${}^{116}\mathrm{Sn}$ at ${T}_{1/2}g~1.3(4.8)\ifmmode\times\else\texttimes\fi{}{10}^{22}$ yr and $g~0.7(2.4)\ifmmode\times\else\texttimes\fi{}{10}^{22}$ yr with 90%(68%) C.L., respectively. For 0\ensuremath{\nu}2\ensuremath{\beta} decay with emission of one or two Majorons, the limits are ${T}_{1/2}(0\ensuremath{\nu}M1)g~3.7(5.8)\ifmmode\times\else\texttimes\fi{}{10}^{21}$ yr and ${T}_{1/2}(0\ensuremath{\nu}M2)g~5.9(9.4)\ifmmode\times\else\texttimes\fi{}{10}^{20}$ yr at 90%(68%) C.L. Restrictions on the value of the neutrino mass, right-handed admixtures in the weak interaction, and the neutrino-Majoron coupling constant are derived as ${m}_{\ensuremath{\nu}}l~2.6(1.4)$ eV, $\ensuremath{\eta}l~3.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8},$ $\ensuremath{\lambda}l~3.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6},$ and ${g}_{M}l~12(9.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ at 90%(68%) C.L., respectively.