The Na2W2O7 crystal: a crystal scintillator for dark matter search experiment

A single crystal of Na 2W 2O 7?(NWO) was grown by a low-thermal-gradient Czochralski technique (LTG-CZ). The scintillation properties of the crystal were evaluated for the first time as a potential material for dark matter search experiments. The luminescence and scintillation characteristics of the crystal were studied at room temperature and low temperatures by using a light-emitting diode (LED) and a 90Sr beta source. The luminescence and scintillation light yield at 10?K were significantly higher than those at room temperature. The crystal showed higher light yield at 10?K than a CaMoO4?(CMO) crystal. The decay time of the crystal was investigated at temperatures between 10 and 300?K. The sensitivity to spin-independent weakly interacting massive particle-nucleon interactions based on 10?kg (2?months) and 50?kg (12?months) data for the NWO crystal detectors was estimated by a simulated experiment using the standard halo model. The luminescence, scintillation, and sensitivity results revealed that the NWO crystal is a promising candidate for a dark matter search experiment in the near future. (c) 2018, The Author(s)11Nsciescopu

Recent progress in oxide scintillation crystals development by low-thermal gradient Czochralski technique for particle physics experiments

International audienceModern particle physics experiments call for high performance scintillation detectors with unique properties: radiation-resistant in high energy and astrophysics, highly radiopure, containing certain elements or enriched isotopes in astroparticle physics. The low-thermal gradient Czochralski (LTG CZ) crystal growth technique provides excellent quality large volume radiopure crystal scintillators. Absence of thermoelastic stress in the crystal and overheating of the melt in the LTG CZ method is particularly significant in production of crystalline materials with strong thermal anisotropic properties and low mechanical strength, with a very high yield of crystalline boules and low losses of initial charge, crucially important in production of crystal scintillators from enriched isotopes for double beta decay experiments. Here we discuss progress in development of the well known scintillators (Bi(4)Ge(3)O(12) (BGO), CdWO(4), ZnWO(4), CaMoO(4), PbMoO(4)), as well as R{&}D of new materials (ZnMoO(4), Li(2)MoO(4), Na(2)Mo(2)O(7)) for the next generation experiments in particle physics

Effects of short-wave therapy in patients with chronic pyelonephritis

One hundred and twenty patients (64 men and 56 women, aged 19 to 63) with chronic pyelonephritis were subdivided into two groups: a control group of 30 subjects and an experimental one of 90 subjects. Experimental subjects underwent short wave therapy (460 MHz, 50-60 W, for 8-20 minutes) in the lumbar area. Lumbosacral pain disappeared in 87 out of 90, subjects, intercostal pain in 20 out of 28, headache mitigated in 40 out of 53, asthenia was markedly reduced in 49 out of 50. Systolic and diastolic hypertension was reduced, as well as the Kakorski-Addis count in urine. Diurnal diuresis and lysozyme increased, while IgG, IgA and IgM were reduced

Preparation of Extra-pure Na2CO3 Powder with Crystallization Techniques for Low-Background Scintillation Crystal Growth

© 2020, Pleiades Publishing, Ltd. A method for the preparation of extra-pure Na2CO3 powder has been developed. The method is based on a fractional crystallization of Na2CO3 from its saturated solutions and its conversion into sodium formate, followed by a melt crystallization. To obtain the final product Na2CO3, the recrystallized sodium formate was thermally decomposed. The contents of Th and U in the purified powder were below 10 ppt, the concentrations of Mn, Co, Ba, and Pb were not above 3 ppb, the concentrations of Cu and Sr were on the level of tens of ppb, and the K concentration was about 200 ppb. The ICP-MS analysis showed that the purity of the obtained powder significantly surpasses that for commercial products in 99.997 and 99.999% purity grades. The sodium carbonate powder thus obtained is going to be used as initial material for growing scintillation single crystals in experiments searching for the neutrinoless double beta decay (0 nu beta beta) or dark matter11Nsciescopu

An MMC-based cryogenic calorimeter with a massive sodium molybdate crystal absorber for neutrinoless double beta decay searches

Sodium molybdate crystals are excellent scintillating target material that can be used to investigate the neutrinoless double beta decay of 100Mo. Because this material contains Na nuclei, it could also be used to clarify the contribution of Na in the controversial claim of dark matter observation by the DAMA/LIBRA experiment. Recent developments have allowed the growth of sodium molybdate crystals of several hundred grams, which makes it possible to build large scale experiments. Therefore, a cryogenic calorimeter with a crystal of significant mass, which can exploit the excellent energy resolution from thermal signals and particle identification using the scintillation signals, is highly desired. We have developed a cryogenic calorimeter with a cylindrical sodium molybdate crystal of 178 g with dimensions of 4 cm (height) × 4 cm (diameter) coupled to a metallic magnetic calorimeter (MMC). The detector was also equipped with a light detector with a thin Ge absorber to detect scintillation signals. The detector test measurements showed excellent energy resolution and particle discrimination using dual detection of heat and light signals, and thus demonstrate that the crystal is a promising tool for searching for rare phenomena events. Details of the detector development with the massive sodium molybdate crystal are discussed in this paper along with the performance results from test measurements.11Nsciescopu

Li2_2100depl^{100\textrm{depl}}MoO4_4 Scintillating Bolometers for Rare-Event Search Experiments

International audienceWe report on the development of scintillating bolometers based on lithium molybdate crystals containing molybdenum depleted in the double-$\beta$ active isotope $^{100}$Mo (Li$_2$$^{100\textrm{depl}}$MoO$_4$). We used two Li$_2$$^{100\textrm{depl}}$MoO$_4$ cubic samples, 45 mm side and 0.28 kg each, produced following purification and crystallization protocols developed for double-$\beta$ search experiments with $^{100}$Mo-enriched Li$_2$MoO$_4$ crystals. Bolometric Ge detectors were utilized to register scintillation photons emitted by the Li$_2$$^{100\textrm{depl}}$MoO$_4$ crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc underground laboratory (Spain). We observed that the Li$_2$$^{100\textrm{depl}}$MoO$_4$ scintillating bolometers are characterized by excellent spectrometric performance ($\sim$3--6 keV FWHM at 0.24--2.6 MeV $\gamma$'s), moderate scintillation signal ($\sim$0.3--0.6 keV/MeV depending on light collection conditions) and high radiopurity ($^{228}$Th and $^{226}$Ra activities are below a few $\mu$Bq/kg), comparable to the best reported results of low-temperature detectors based on Li$_2$MoO$_4$ with natural or $^{100}$Mo-enriched molybdenum content. Prospects of Li$_2$$^{100\textrm{depl}}$MoO$_4$ bolometers for use in rare-event search experiments are briefly discussed

Li2_2100depl^{100\textrm{depl}}MoO4_4 Scintillating Bolometers for Rare-Event Search Experiments

International audienceWe report on the development of scintillating bolometers based on lithium molybdate crystals containing molybdenum depleted in the double-$\beta$ active isotope $^{100}$Mo (Li$_2$$^{100\textrm{depl}}$MoO$_4$). We used two Li$_2$$^{100\textrm{depl}}$MoO$_4$ cubic samples, 45 mm side and 0.28 kg each, produced following purification and crystallization protocols developed for double-$\beta$ search experiments with $^{100}$Mo-enriched Li$_2$MoO$_4$ crystals. Bolometric Ge detectors were utilized to register scintillation photons emitted by the Li$_2$$^{100\textrm{depl}}$MoO$_4$ crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc underground laboratory (Spain). We observed that the Li$_2$$^{100\textrm{depl}}$MoO$_4$ scintillating bolometers are characterized by excellent spectrometric performance ($\sim$3--6 keV FWHM at 0.24--2.6 MeV $\gamma$'s), moderate scintillation signal ($\sim$0.3--0.6 keV/MeV depending on light collection conditions) and high radiopurity ($^{228}$Th and $^{226}$Ra activities are below a few $\mu$Bq/kg), comparable to the best reported results of low-temperature detectors based on Li$_2$MoO$_4$ with natural or $^{100}$Mo-enriched molybdenum content. Prospects of Li$_2$$^{100\textrm{depl}}$MoO$_4$ bolometers for use in rare-event search experiments are briefly discussed

Aboveground test of an advanced Li2_2MoO4_4 scintillating bolometer to search for neutrinoless double beta decay of 100^{100}Mo

Large lithium molybdate (Li2MoO4) crystal boules were produced by using the low thermal gradient Czochralski growth technique from deeply purified molybdenum. A small sample from one of the boules was preliminary characterized in terms of X-ray-induced and thermally-excited luminescence. A large cylindrical crystalline element (with a size of circle divide 40 x 40 mm) was used to fabricate a scintillating bolometer, which was operated aboveground at similar to 15 mK by using a pulse-tube cryostat housing a high-power dilution refrigerator. The excellent detector performance in terms of energy resolution and alpha background suppression along with preliminary positive indications on the radiopurity of this material show the potentiality of Li2MoO4 scintillating bolometers for low-counting experiment to search for neutrinoless double beta decay of Mo-100. (C) 2015 Elsevier B.V. All rights reserved

New measurement of double beta decays of 100^{100}Mo to excited states of 100^{100}Ru with the CUPID-Mo experiment

The CUPID-Mo experiment, located at Laboratoire Souterrain de Modane (France), was a demonstrator experiment for CUPID. It consisted of an array of 20 Li$_2^{100}$MoO$_4$ (LMO) calorimeters each equipped with a Ge light detector (LD) for particle identification. In this work, we present the result of a search for two-neutrino and neutrinoless double beta decays of $^{100}$Mo to the first 0$^+$ and $2^+$ excited states of $^{100}$Ru using the full CUPID-Mo exposure (2.71 kg$\times$yr of LMO). We measure the half-life of $2\nu\beta\beta$ decay to the $0^{+}_1$ state as $T_{1/2}^{2\nu \rightarrow 0_1^+}=7.5\pm 0.8 \ \text{(stat.)} \ ^{+ 0.4}_{-0.3} \ \text{(syst.)} )\times 10^{20} \ \mathrm{yr}$. The bolometric technique enables measurement of the electron energies as well as the gamma rays from nuclear de-excitation and this allows us to set new limits on the two-neutrino decay to the $2_1^+$ state of T^{2\nu \rightarrow 2_1^+}_{1/2}>4.4\times 10^{21} \ \mathrm{yr} \ \text{(90 % c.i.)} and on the neutrinoless modes of T_{1/2}^{0\nu\rightarrow 2_1^+}>2.1\times10^{23} \ \mathrm{yr}\ \text{(90 % c.i.)}, T_{1/2}^{0\nu\rightarrow 0_1^+}>1.2\times10^{23} \ \mathrm{yr}\ \text{(90 % c.i.)}. Information on the electrons spectral shape is obtained which allows us to make the first comparison of the single state (SSD) and higher state (HSD) $2\nu\beta\beta$ decay models for the $0_1^+$ excited state of $^{100}$Ru