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CUPID-Mo is a bolometric experiment to search for neutrinoless double-beta decay ( 0 ν β β ) of 100 Mo . In this article, we detail the CUPID-Mo detector concept, assembly and installation in the Modane underground laboratory, providing results from the first datasets. The CUPID-Mo detector consists of an array of 20 100 Mo -enriched 0.2 kg Li 2 MoO 4 crystals operated as scintillating bolometers at ∼ 20 mK . The Li 2 MoO 4 crystals are complemented by 20 thin Ge optical bolometers to reject α events by the simultaneous detection of heat and scintillation light. We observe a good detector uniformity and an excellent energy resolution of 5.3 keV (6.5 keV) FWHM at 2615 keV, in calibration (physics) data. Light collection ensures the rejection of α particles at a level much higher than 99.9% – with equally high acceptance for γ / β events – in the region of interest for 100 Mo 0 ν β β . We present limits on the crystals’ radiopurity: ≤ 3 μ Bq/kg of 226 Ra and ≤ 2 μ Bq/kg of 232 Th . We discuss the science reach of CUPID-Mo, which can set the most stringent half-life limit on the 100 Mo 0 ν β β decay in half-a-year’s livetime. The achieved results show that CUPID-Mo is a successful demonstrator of the technology developed by the LUMINEU project and subsequently selected for the CUPID experiment, a proposed follow-up of CUORE, the currently running first tonne-scale bolometric 0 ν β β experiment.

We report on the development of scintillating bolometers based on lithium molybdate crystals that contain molybdenum that has depleted into the double-β active isotope 100Mo (Li2100deplMoO4). We used two Li2100deplMoO4 cubic samples, each of which consisted of 45-millimeter sides and had a mass of 0.28 kg; these samples were produced following the purification and crystallization protocols developed for double-β search experiments with 100Mo-enriched Li2MoO4 crystals. Bolometric Ge detectors were utilized to register the scintillation photons that were emitted by the Li2100deplMoO4 crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc Underground Laboratory (Spain). We observed that the Li2100deplMoO4 scintillating bolometers were characterized by an excellent spectrometric performance (∼3–6 keV of FWHM at 0.24–2.6 MeV γs), moderate scintillation signal (∼0.3–0.6 keV/MeV scintillation-to-heat energy ratio, depending on the light collection conditions), and high radiopurity (228Th and 226Ra activities are below a few µBq/kg), which is comparable with the best reported results of low-temperature detectors that are based on Li2MoO4 using natural or 100Mo-enriched molybdenum content. The prospects of Li2100deplMoO4 bolometers for use in rare-event search experiments are briefly discussed.

The AMoRE collaboration conducts experiments to search for the neutrinoless double beta decay of 100 Mo using massive Li 2 MoO 4 (LMO) crystals in a cryogenic calorimetric detection with metallic magnetic calorimeters (MMCs). The detector module incorporates a light detector with Si or Ge wafers, enabling the simultaneous detection of scintillation light. The forthcoming phase (AMoRE-II) of the experiment will include 6 cm (diameter) × 6 cm (height) LMO cylindrical crystals, and this has been chosen to reduce the number of crystals and sensors. Additionally, these crystals will have diffusive surfaces rather than polished ones, which helps to reduce the crystal preparation time. The phonon signal of crystals with diffusive surfaces is slower than that of polished crystals. However, due to the mitigated position dependence, diffusive crystals exhibit better discrimination between α and β / γ signals by pulse shape analysis. We also found that muon events show two bands in the rise time of the large LMO crystal with polished surface, indicating the muon passage at the edge of the crystal, and the band structure is significantly mitigated in the crystals with the diffusive surfaces. To study the position dependence in the crystal absorber further, we irradiated some R&D detectors with localized α sources. This paper discusses the particle identification and position dependence of γ , α , and muon events for the large AMoRE-II type detectors based on the pulse shape analysis.

The AMoRE collaboration is preparing for the AMoRE-II experiment that will probe neutrinoless double beta decay with 100 kg of 100 Mo isotope. The 100 Mo nuclide will be mainly in the form of lithium molybdate crystals that are instrumented with metallic magnetic calorimeters (MMC), which detect the phonon excitations produced by electrons from neutrinoless double beta decay in the crystals. The energy resolution at a Q -value = 3.034 MeV is around 10 keV within a temperature ranging between 10 and 20 mK. Increasing the crystal mass of individual detector modules will reduce the number of detector channels and allow a few practical advantages associated with crystal growing, detector preparation, and operation of the experiment. To this end, we carried out an experiment with a 6 cm (diameter (D)) × 6 cm (height (H)) cylindrical lithium molybdate crystal of 516 g mass, which is 73% more massive than the 5 cm (D) × 5 cm (H) crystals that are currently being used in the AMoRE-I setup. We found that the larger crystal detector shows good performance characteristics in terms of energy resolution, signal time constant and particle identification capability, which makes it a suitable option for the AMoRE-II experiment.

The bulk of the LiNa5Mo9O30 (LNM) crystals were successfully grown in the [010] and [001] directions without internal inclusions and cracks, using the Czochralski method with a low temperature gradient. The crystal grown in the [010] direction showed a tendency to twinning. The crystal grown in the [001] direction demonstrated high structural perfection (FWHM = 13″) for the (001) plane and high optical quality Δn ≈ 2 × 10−5. The laser-induced damage threshold was measured along a, b and c axes and was 12.2, 27.0 and 27.5 J/cm2, respectively. The thermo-optical coefficient dn/dT was measured for the main crystallographic axes, which was −5.75 × 10−6, −20.2 × 10−6 and 3.65 × 10−6 K−1 along the a, b and c axes, respectively. The second harmonic generation (SHG) was conducted in the crystalline LNM sample. The maximum efficiency value of 3.5% at a pump power of 12 W was achieved.

Heteroatom doping is one of the most promising strategies toward regulating intrinsically sluggish electronic conductivity and kinetic reaction of transition metal oxides for enhancing their lithium storage. Herein, we designed phosphorus-doped NiMoO 4 nanorods (P-NiMoO 4 ) by using a facile hydrothermal method and subsequent low-temperature phosphorization treatment. Phosphorus doping played an indispensable role in significantly improving electronic conductivity and the Li + diffusion kinetics of NiMoO 4 materials. Experimental investigation and density functional theory calculation demonstrated that phosphorus doping can expand the interplanar spacing and alter electronic structures of NiMoO 4 nanorods. Meanwhile, the introduced phosphorus dopant can generate some oxygen vacancies on the surface of NiMoO 4 , which can accelerate Li + diffusion kinetics and provide more active site for lithium storage. As excepted, P-NiMoO 4 electrode delivered a high specific capacity (1,130 mAh·g −1 at 100 mA·g −1 after 100 cycles), outstanding cycling durability (945 mAh·g −1 at 500 mA·g −1 over 200 cycles), and impressive rate performance (640 mAh·g −1 at 2,000 mA·g −1 ) for lithium ion batteries (LIBs). This work could provide a potential strategy for improving intrinsic conductivity of transition metal oxides as high-performance anodes for LIBs.

Lithium-rich transition metal oxide (Li 1+ X M 1− X O 2 ) cathodes have high energy density above 900 Wh kg −1 due to hybrid anion- and cation-redox (HACR) contributions, but critical issues such as oxygen release and voltage decay during cycling have prevented their application for years. Here we show that a molten molybdate-assisted LiO extraction at 700 °C creates lattice-coherent but depth ( r )-dependent Li 1+ X ( r ) M 1− X ( r ) O 2 particles with a Li-rich ( X  ≈ 0.2) interior, a Li-poor ( X  ≈ −0.05) surface and a continuous gradient in between. The gradient Li-rich single crystals eliminate the oxygen release to the electrolyte and, importantly, still allow stable oxygen redox contributions within. Both the metal valence states and the crystal structure are well maintained during cycling. The gradient HACR cathode displays a specific density of 843 Wh kg −1 after 200 cycles at 0.2C and 808 Wh kg −1 after 100 cycles at 1C, with very little oxygen release and consumption of electrolyte. This high-temperature immunization treatment can be generalized to leach other elements to avoid unexpected surface reactions in batteries. Critical issues such as oxygen release during battery cycling plague the development of high-energy Li-rich oxide cathodes. Here the authors report a Li-gradient structure of the oxides, obtained by a selective LiO leaching process via a molten salt treatment, displaying virtually zero oxygen loss.

Mo-doped V2O5 hierarchical nanorod/nanoparticle core/shell porous microspheres (MVHPMs) were prepared via a simple hydrothermal approach using ammonium metavanadate and ammonium molybdate as precursors followed by a thermal annealing process. The samples were characterized by XRD, SEM, TEM, EDS, and XPS carefully; it confirmed that porous microspheres with uniform Mo doping in the V2O5 matrix were obtained, and it contains an inner core self-assembled with 1D nanorods and outer shell consisting of nanoparticles. A plausible growth mechanism of Mo-doped V2O5 (Mo-V2O5) porous microspheres is suggested. The unique microstructure made the Mo-V2O5 hierarchical microspheres a good cathode material for Li-ion battery. The results indicate the synthesized Mo-V2O5 hierarchical microspheres exhibit well-improved electrochemical performance compared to the undoped samples. It delivers a high initial reversible capacity of 282 mAh g−1 at 0.2 C, 208 mAh g−1 at 2 C, and 111 mAh g−1 at 10 C, and it also exhibits good cycling stabilities; a capacity of 144 mAh g−1 is obtained after 200 cycles at 6 C with a capacity retention of > 82%, which is much high than that of pure V2O5 (95 mAh g−1 with a capacity retention of 72%).

Highly efficient fluorescent and biocompatible europium doped sodium zinc molybdate (NZMOE) nanoprobes were successfully synthesized via Polyol method. Non-radiative defect centres get reduced with Li + co-doping in NZMOE nanoprobes. XRD spectra and Rietveld refinement confirmed successful incorporation of lithium ion and crystallinity was also improved with Li + co-doping. The shape of phosphor is rod shaped, as determined by TEM. Significant enhancement in photoluminescence intensity was observed with 266, 395 and 465 nm excitations. Profound red emission was recorded for 5 at% Li + co-doped NZMOE nanoprobes with 266 nm excitation. It shows high asymmetry ratio (~15), color purity (94.90%) and good quantum efficiency (~70%). Judd Ofelt parameters have been calculated to measure intensity parameters and radiative transition rates. In order to measure biocompatibility of the nanoprobes, cytotoxicity assays were performed with HePG2 cells. The fluorescence emitted from phosphor material treated HePG2 cells was also measured by Laser Scanning Confocal Microscopy. The bright red fluorescence in HePG2 cells treated with very low concentration (20 μg/ml) of phosphor material indicates that it could be a promising phosphor for biological detection or bio-imaging.