Development of thermal neutron shield with low radioactivity

The second phase of the Advanced Mo-based Rare process Experiment (AMoRE-II) searches for a neutrino-less double-beta decay of 100Mo. A background level in the region of interest of 3034 & PLUSMN; 10 keV is required to be lower than 10-4 count/(keV kg year). Neutrons can generate background signals by gamma-ray emitting reactions with AMoRE-II detector materials. Thermal neutron shields will be installed inside and outside the lead shield to reduce the neutron flux in the shielding system. The background radioactivity of the inner thermal neutron shield must be low because AMoRE-II requires a low background level. A thermal neutron shield with a high shielding efficiency and low radioactivity was produced by using boric acid powder and silicone rubber. The shielding efficiency was tested to be {99.2 +/- 0.25(stat)?0.47 -0.53(syst)}%, and the radioactivities of 40K, Ra-226, Ac-228, and Th-228 were measured to be < 9.2 at 90% C.L., 14.2 +/- 1.5, < 1.6 at 90% C.L., and 2.83 +/- 0.80 mBq/kg, respectively.11Nsciescopu

Compositional engineering of perovskite materials for high-performance solar cells

Of the many materials and methodologies aimed at producing low-cost, efficient photovoltaic cells, inorganic&#8211;organic lead halide perovskite materials appear particularly promising for next-generation solar devices owing to their high power conversion efficiency. The highest efficiencies reported for perovskite solar cells so far have been obtained mainly with methylammonium lead halide. Here we combine the promising&#8212;owing to its comparatively narrow bandgap&#8212;but relatively unstable formamidinium lead iodide (FAPbI3) with methylammonium lead bromide (MAPbBr3) as the light-harvesting unit in a bilayer solar-cell architecture13. We investigated phase stability, morphology of the perovskite layer, hysteresis in current&#8211;voltage characteristics, and overall performance as a function of chemical composition. Our results show that incorporation of MAPbBr3 into FAPbI3 stabilizes the perovskite phase of FAPbI3 and improves the power conversion efficiency of the solar cell to more than 18 per cent under a standard illumination of 100 milliwatts per square centimetre. These findings further emphasize the versatility and performance potential of inorganic&#8211;organic lead halide perovskite materials for photovoltaic applications.clos

Status of the AMoRE Experiment Searching for Neutrinoless Double Beta Decay Using Low-Temperature Detectors

The goal of the Advanced Mo-based Rare process Experiment (AMoRE) is to search for the neutrinoless double beta decay of Mo-100 using low-temperature detectors consisting of Mo-based scintillating crystals read out via metallic magnetic calorimeters. Heat and light signals are measured simultaneously at millikelvin temperatures, which are reached using a cryogen-free dilution refrigerator. The AMoRE-Pilot experiment, using six Mo-100-enriched, Ca-48-depleted calcium molybdate crystals with a total mass of about 1.9 kg, has been running in the 700-m-deep Yangyang underground laboratory as the pilot phase of the AMoRE project. Several setup improvements through different runs allowed us to achieve a high energy resolution and an efficient particle discrimination. This article briefly presents the status of the AMoRE-Pilot experiment, as well as the plans for the next, larger-scale, experimental stages. © Springer Science+Business Media, LLC, part of Springer Nature 201811sci

Vertically Ordered Hematite Nanotube Array as an Ultrasensitive and Rapid Response Acetone Sensor

Vertically ordered nanotube array is a desirable configuration to improve gas sensing properties of the hematite which is the most abundant and cheapest metal oxide semiconductor on earth but has low and sluggish chemiresistive responses. We have synthesized a vertically aligned, highly ordered hematite nanotube array directly on a patterned SiO2/Si substrate and then it used as a gas sensor without additional processing. The nanotube array sensor shows unprecedentedly ultrahigh and selective responses to acetone with detection limits down to a few parts per billion and response time shorter than 3 s.close