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A first search for rare decays of gadolinium isotopes was performed with an ultra-low background high-purity germanium detector at Gran Sasso Underground Laboratory (Italy). A 198 g Gd 2 O 3 powder sample was measured for 63.8 d with a total Gd exposure of 12.6 kg × d. 152 Gd is the most promising isotope for resonant enhanced neutrinoless double electron capture which could significantly increase the decay rate over other neutrinoless double beta decay processes. The half-life for this decay was constrained to > 4.2 × 10 12 year (90% credibility). This limit is still orders of magnitude away from theoretical predictions but it is the first established limit on the transition paving the way for future experiments. In addition, other rare alpha and double beta decay modes were investigated in 152 Gd, 154 Gd, and 160 Gd with half-life limits in the range of 10 17 - 20 year. [ABSTRACT FROM AUTHOR]

180 m Ta is the longest-lived metastable state presently known. Its decay has not been observed yet. In this work, we report a new result on the decay of 180 m Ta obtained with a 2015.12-g tantalum sample measured for 527.7 d with an ultra-low background HPGe detector in the STELLA laboratory of the Laboratori Nazionali del Gran Sasso (LNGS), in Italy. Before the measurement, the sample has been stored deep-underground for ten years, resulting in subdominant background contributions from cosmogenically activated 182 Ta . We observe no signal in the regions of interest and set half-life limits on the process for the two channels EC and β - : T 1 / 2 , EC > 1.6 × 10 18 year and T 1 / 2 , β - > 1.1 × 10 18 year (90% C. I.), respectively. We also set the limit on the γ de-excitation / IC channel: T 1 / 2 , IC > 4.1 × 10 15 year (90% C. I.). These are, as of now, the most stringent bounds on the decay of 180 m Ta worldwide. Finally, we test the hypothetical scenarios of de-excitation of 180 m Ta by cosmological Dark Matter and constrain new parameter space for strongly-interacting dark-matter particle with mass up to 10 5 GeV. [ABSTRACT FROM AUTHOR]

In this work, we present the first complex study of Cs 2 ZrCl 6 (CZC) scintillating crystals in terms of their chemical purity, crystal radiopurity, scintillating performance and pulse-shape discrimination ability. An ICP-MS measurement exhibits a high purity of the CZC material (overall impurity level less than 10 μ g/g). The CZC crystals show a very low content of radionuclides from U/Th natural decay chains. For 40 K and 137 Cs only limits at the level few mBq/kg were set after more than 650 h of measurement with a high purity germanium (HPGe) detector. Nevertheless, they contained cosmogenic 134 Cs with an activity of about 50 mBq/kg. The measurements with two CZC crystals (11 and 24 g) as scintillating detectors over 456.5 d in the low-background DAMA/CRYS facility, deep underground at LNGS, supported a substantial radiopurity of these crystals leading to a counting rate of 0.17 - 0.11 + 0.13 (kg · keV · yr) - 1 at the Q 2 β of 96 Zr (3.35 MeV). These detectors show a high particle-discrimination ability for β (γ) and α particles. Limits on the half-lives of the double beta decays (DBD) of 96 Zr and of 94 Zr with and without neutrinos emission were also set at the level T 1 / 2 ∼ 10 17 – 10 20 yr (90 % C.L.). The detailed analyses of the internal background components will also be useful for further developments of Cs 2 ZrCl 6 low-background scintillating detectors and for the optimization of the experimental conditions. [ABSTRACT FROM AUTHOR]

A new study of double beta decay processes in natural Zr isotopes using Zr metal samples and an ultra-low-background high-purity germanium detectors was performed at Laboratori Nazionali del Gran Sasso of INFN (Italy). Two data sets were collected with a 736.35 g and a 129.94 g Zr metal over 59.7 days and 37.3 days, respectively, and were used for a detailed analysis. A new limit on the double beta decay of 94 Zr to the 1st excited level of 94 Mo was set as T 1 / 2 β β > 2.1 × 10 20 year , which is a factor of three better than the previous result. It is shown that the current radiopurity of Zr metal (tens of Bq/kg), produced via two methods, do not comply with the radiopurity requirements for low-background experiments. Hence, we propose to use a purified ZrCl 4 powder in an optimized geometry as a new approach for future experiments with extended sensitivity focused on studies of rare nuclear processes in Zr isotopes. [ABSTRACT FROM AUTHOR]

A 510 day long-term measurement of a 45.3 g platinum foil acting as the sample and high voltage contact in an ultra-low-background high purity germanium detector was performed at Laboratori Nazionali del Gran Sasso (Italy). The data was used for a detailed study of double beta decay modes in natural platinum isotopes. Limits are set in the range O (10 14 - 10 19) years (90% C.L.) for several double beta decay transitions to excited states confirming, and partially extending existing limits. The highest sensitivity of the measurement, greater than 10 19 years, was achieved for the two neutrino and neutrinoless double beta decay modes of the isotope 198 Pt. Additionally, novel limits for inelastic dark matter scattering on 195 Pt are placed up to mass splittings of approximately 500 keV. We analyze several techniques to extend the sensitivity and propose a few approaches for future medium-scale experiments with platinum-group elements. [ABSTRACT FROM AUTHOR]

Recently, efforts on the building of Hf-based crystal scintillators have been performed. The so-called "source = detector" approach has been implemented to study rare nuclear processes in Hf isotopes with higher efficiency with respect to the HP-Ge spectrometry. In this work, a review of recent studies concerning rare nuclear processes in Hf isotopes are presented. [ABSTRACT FROM AUTHOR]

Lead isotope compositions were determined for 18 metal objects from the archaeological site of Sant’Imbenia, NW Sardinia, dating to the end of the ninth century BCE onwards. The provenance of some objects is unambiguously traced to SW Sardinia; other objects could derive either from central Sardinia or the Iberian coastal ranges. The variety of the provenances attests to a wide trade network that spanned the entire island of Sardinia and extended to the Iberian sites. [ABSTRACT FROM AUTHOR]

A search for resonant absorption of solar axions by 169 Tm nuclei was carried out. A newly developed approach involving low-background cryogenic bolometer based on Tm 3 Al 5 O 12 crystal was used that allowed for significant improvement of sensitivity in comparison with previous 169 Tm based experiments. The measurements performed with 8.18 g crystal during 6.6 days exposure yielded the following limits on axion couplings: | g A γ (g AN 0 + g AN 3) ≤ 1.44 × 10 - 14 GeV - 1 and | g Ae (g AN 0 + g AN 3) ≤ 2.81 × 10 - 16 . [ABSTRACT FROM AUTHOR]

We operated a PbMoO 4 scintillating cryogenic detector of 570 g, produced with archaeological lead. This compound features excellent low temperature characteristics in terms of light yield, 12 keV/MeV for β / γ interactions, and FWHM energy resolution, 11.7 keV at 2.6 MeV. Furthermore, the detector allows for an effective particle identification by means of pulse shape analysis on the heat read-out channel. The implementation of innovative techniques and procedures for the purification of raw materials used for the crystal growth, and the highly-pure archaeological Pb, allowed for the production of large volume high-quality crystal. The overall characteristics of the detector operated at cryogenic temperatures makes PbMoO 4 an excellent compound for neutrino physics applications, especially neutrinoless double-beta studies. [ABSTRACT FROM AUTHOR]

The first direct search for the double electron capture ( 2 ε ) and the electron capture with positron emission ( ε β + ) in 144Sm to the ground state and to the excited levels of 144Nd was realized by measuring --over 1899h-- a 342g sample of highly purified samarium oxide (Sm2O3) with the ultra-low background HP-Ge γ spectrometer GeCris (465cm3) at the STELLA facility of the Gran Sasso National Laboratory (LNGS). No effect was observed and half-life limits were estimated at the level of T 1 / 2 ∼ (0. 1 - 1. 3) × 10 20 yr (90% C.L.). Moreover, for the first time half-life limits of the double beta ( 2 β - ) decay of 154Sm to several excited levels of 154Gd have been set; they are at the level of T 1 / 2 ∼ (0. 06 - 8) × 10 20 yr (90% C.L.). [ABSTRACT FROM AUTHOR]

Assessment of radioactive contamination of construction materials used in deep underground experiments has been carried out using ultra-sensitive analytical methods such as radiometrics, inductively coupled plasma mass spectrometry (ICPMS), accelerator mass spectrometry (AMS), and neutron activation analysis. The lowest detection limits, < 1 nBq g−1, has been obtained with ICPMS and AMS techniques. [ABSTRACT FROM AUTHOR]

This paper describes the production and chemical separation of the 163Ho isotope that will be used in several nuclear physics experiments aiming at measuring the neutrino mass as well as the neutron cross section of the 163Ho isotope. For this purpose, several batches of enriched 162Er have been irradiated at the Institut Laue-Langevin high flux reactor to finally produce 6 mg or 100 MBq of the desired 163Ho isotope. A portion of the Er/Ho mixture is then subjected to a sophisticated chemical separation involving ion exchange chromatography to isolate the Ho product from the Er target material. Before irradiation, a thorough analysis of the impurity content was performed and its implication on the produced nuclide inventory will be discussed. [ABSTRACT FROM AUTHOR]

Rare events search experiments, like those dedicated to the direct evidence of dark matter or neutrinoless double beta decay, are among the most exciting challenges of modern physics. The sensitivity of such experiments is driven by the background, which depends substantially on the radiopurity of the materials used for the experimental apparatus. Cutting edge measurement techniques are needed for a fast, sensitive and efficient screening of these materials and the certification of their production. Trace element measurements of high sensitivity and quick execution are mandatory also in other fields like tracing the geographical origin of food, temporal and geographical assignment of cultural heritage or monitoring environmental radioactivity. This work is an overview of the inorganic mass spectrometry facility available at Gran Sasso National Laboratory (LNGS) for radiopure material screening and is especially focused on its ICP-MS instrumentation. Analytical methods developed to achieve lowest detection limits in different types of matrix, like metals, polymers, crystals and composite materials, are also indicated. Detection limits of for , for U and Th and for K are attained through dedicated operation conditions of the instrumentation. Details are given on the results obtained for different experiments ongoing or under construction at LNGS. [ABSTRACT FROM AUTHOR]

In the view of exploring the inverted hierarchy region future experiments investigating the neutrinoless double beta decay have to demand for detectors with excellent energy resolution and zero background in the energy region of interest. Cryogenic scintillating bolometers are very suitable detectors for this task since they provide particle discrimination: the simultaneous detection of the phonon and light signal allows us to identify the interacting type of particle and thus guarantees a suppression of $$\alpha $$ -induced backgrounds, the key-issue for next-generation tonne-scale bolometric experiments. The LUCIFER project aims at running the first array of enriched scintillating Zn $$^{\text {82}}$$ Se bolometers (total mass of about 8kg of $$^{\text {82}}$$ Se) with a background level as low as 10 $$^{\text {--3}}$$ counts/(keV kg y) in the energy region of interest. The main effort is currently focused on the finalization of the crystal growth procedure in order to achieve high quality Zn $$^{\text {82}}$$ Se crystals both in terms of radiopurity and bolometric properties. We present results from tests of such crystals operated at mK temperatures which demonstrate the excellent background rejection capabilities of this detection approach towards a background-free demonstrator experiment. Besides, the high purity of the enriched $$^{\text {82}}$$ Se material allows us to establish the most stringent limits on the half-life of the double beta decay of $$^{\text {82}}$$ Se on excited levels. [ABSTRACT FROM AUTHOR]

The detection of $$^{148}$$ Sm alpha decay with a precise measured half-life of $$\left( {6.4_{-1.3}^{+1.2} }\right) \times 10^{15}y$$ and a Q-value of 1987.3 $$\pm $$ 0.5 keV was achieved by a new experimental approach, where a conventional ZnWO $$_{4}$$ scintillating crystal doped with enriched $$^{148}$$ Sm isotope is operated as a cryogenic scintillating bolometer (phonon and light channel) at mK-temperatures. [ABSTRACT FROM AUTHOR]

In the field of fundamental particle physics, the neutrino has become more and more important in the last few years, since the discovery of its mass. In particular, the ultimate nature of the neutrino (if it is a Dirac or a Majorana particle) plays a crucial role not only in neutrino physics, but also in the overall framework of fundamental particle interactions and in cosmology. The only way to disentangle its ultimate nature is to search for the neutrinoless double beta decay. The idea of LUCIFER is to combine the bolometric technique proposed for the CUORE experiment with the bolometric light detection technique used in cryogenic dark matter experiments. The bolometric technique allows an extremely good energy resolution while its combination with the scintillation detection offers an ultimate tool for background rejection. The goal of LUCIFER is not only to build a background-free small-scale experiment but also to directly prove the potentiality of this technique. Preliminary tests on several detectors containing different interesting DBD emitters have clearly demonstrated the excellent background rejection capabilities that arise from the simultaneous, independent, double readout of heat and scintillation light. [ABSTRACT FROM AUTHOR]

A new Nd-loaded liquid organic scintillator based on pseudocumene (PC) solvent was developed for the experiment aimed at searching for 0νββ decay of a Nd nucleus. The optical characteristics of the scintillator were measured for several Nd concentrations. The measurements taken using two modules 1 and 2 m in length have made it possible to determine the effective attenuation length of the PC scintillator containing Nd (6.5 g/L). It was demonstrated that the scintillator characteristics remained unaltered over 1 year. The content of radioactive contaminants was analyzed, and the sensitivity of the experiment to effective Majorana neutrino mass 〈 m〉 ∼ 0.05-0.10 eV was estimated for a detector containing a 12-ton scintillator. [ABSTRACT FROM AUTHOR]

The Th content in commercially available NdO samples with the main substance content of 99.0-99.998% was found to be 2-8, and that of U, 3-230 ppb. Therefore, to obtain Nd meeting the requirements of the experiment on studying neutrinoless double β-decay, it should be purified to reduce the content of Th and U impurities by a factor of 10-10. To this end, the extraction of Nd, Th, and U from hydrochloric acid media with solutions of trioctylphosphine oxide (TOPO) in toluene was studied. The distribution ratios of Th increase with a decrease in the HCl concentration in the initial aqueous solution. With an increase in the Cl concentration in the aqueous phase, the U distribution ratios decrease, probably because of a decrease in the concentration of the free extractant due to the extraction of Nd and HCl. On the contrary, the distribution ratios of Th increase with an increase in the Cl concentration in the aqueous phase, with the slope of the straight line in the coordinates log D-log[Cl] close to 7, which may be due to coextraction of Th with Nd in the form of the complex ThNdCl. The enthalpies of formation of the extractable complexes of Th and U were determined from the temperature dependence of the extraction of Nd, Th, and U chlorides with a 0.1 M solution of TOPO in toluene. The optimal extraction system was chosen for Nd purification to remove traces of Th and U: organic phase, 0.1 M solution of TOPO in toluene; aqueous phase, 2.4 M NdCl + 0.1 M HCl. From the initial aqueous solution contaning 574 ppt Th and 2837 ppt U, by single extraction with an equal volume of 0.1 M TOPO in toluene, an aqueous solution containing <10 ppt Th and 31 ppt U (detection limit 10 ppt) was obtained. By semicountercurrent extraction, from the initial aqueous NdCl3 solution containing 200 ppb Th, the raffinate containing <10 ppt Th was obtained in one extraction step. The results obtained confirm the possibility of exhaustive removal of Th and U impurities (to the level of ≤1 ppt) from Nd by extraction with TOPO solutions from chloride solutions. [ABSTRACT FROM AUTHOR]

Based on purification efficiency calculations for lead distillation, we developed a combined process for the ultrapurification of archaeological lead. We obtained pilot amounts of high-purity archaeological lead and PbO with the following contents of detrimental impurities: U, <2 ppb; Th, <1 ppb; Ni, Cu, Fe, Si, Ti, Mg, Al, Mn, Cr, V, Co, < 0.1 ppm; K, Ca, Zn, Cd, Ag, Sb, < 1 ppm. Lead of such purity can be used in low-background experiments as a protective shield material and in the growth of low-background PbWO and PbMoO scintillator crystals. From an isotope ratio, we were able to identify the origin of the archaeological lead. [ABSTRACT FROM AUTHOR]

The ability to predict earthquakes is one of the greatest challenges for Earth Sciences. Radon has been suggested as one possible precursor, and its groundwater anomalies associated with earthquakes and water-rock interactions were proposed in several seismogenic areas worldwide as due to possible transport of radon through microfractures, or due to crustal gas fluxes along active faults. However, the use of radon as a possible earthquake's precursor is not clearly linked to crustal deformation. It is shown in this paper that uranium groundwater anomalies, which were observed in cataclastic rocks crossing the underground Gran Sasso National Laboratory, can be used as a possible strain meter in domains where continental lithosphere is subducted. Measurements evidence clear, sharp anomalies from July, 2008 to the end of March, 2009, related to a preparation phase of the seismic swarm, which occurred near L'Aquila, Italy, from October, 2008 to April, 2009. On April 6th, 2009 an earthquake (M = 6.3) occurred at 01:33 UT in the same area, with normal faulting on a NW-SE oriented structure about 15 km long, dipping toward SW. In the framework of the geophysical and geochemical models of the area, these measurements indicate that uranium may be used as a possible strain meter in extensional tectonic settings similar to those where the L'Aquila earthquake occurred. [ABSTRACT FROM AUTHOR]

Recently ZnWO4 was proposed as perspective material for low-counting experiments to search for rare processes. Such experiments demand high radiopurity of ZnWO4 crystal scintillators. With this aim radioactive contamination of large volume (0.1-0.7 kg) ZnWO4 crystal scintillators were measured in the underground Laboratori Nazionali del Gran Sasso of the INFN at the depth of ≈ 3600 m water equivalent. [ABSTRACT FROM AUTHOR]

The main purpose of the Cryogenic Underground Observatory for Rare Events (CUORE) experiment is the search for the Neutrinoless Double Beta Decay (0νDBD) of 130Te reaching a sensitivity on Majorana mass better than 50 meV. Cuoricino represents not only the first stage of CUORE, but also the most massive 0νDBD experiment presently running. Present results and future planning of these experiments will be described in the paper. [ABSTRACT FROM AUTHOR]

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 YVO4 crystal aiming at the investigation of the 4-fold forbidden non-unique β- decay of 50V. 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, 235/238U and 232Th 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 50V β- decay. [ABSTRACT FROM AUTHOR]

We report on the first compelling observation of α decay of 151Eu to the ground state of 147Pm. The measurement was performed using a 6.15 g Li6Eu(BO3)3 crystal operated as a scintillating bolometer. The Q-value and half-life measured are: Q = 1948.9±6.9(stat.) ± 5.1(syst.) keV, and T1/2 = (4.62 ± 0.95(stat.) ± 0.68(syst.)) × 1018 y. The half-life prediction of nuclear theory using the Coulomb and proximity potential model are in good agreement with this experimental result. [ABSTRACT FROM AUTHOR]