Phase Transitions in Terbium Oxide Nanopowders Synthesized by Laser Ablation under Various Buffer Gases

Synthesis of nanosized particles of terbium oxide by laser ablation under various buffer gases is reported. Influence of the gas composition (air, Ar, Ar+H2) on the morphology, average particle size and phase evolution during heating up was investigated.The reported study was carried out with the use of grant № 22-23-00658 of the Russian Science Foundation, https://rscf.ru/en/project/22-23-00658

Formation of "Lightnings" in a Neutron Star Magnetosphere and the Nature of RRATs

The connection between the radio emission from "lightnings" produced by the absorption of high-energy photons from the cosmic gamma-ray background in a neutron star magnetosphere and radio bursts from rotating radio transients (RRATs) is investigated. The lightning length reaches 1000 km; the lightning radius is 100 m and is comparable to the polar cap radius. If a closed magnetosphere is filled with a dense plasma, then lightnings are efficiently formed only in the region of open magnetic field lines. For the radio emission from a separate lightning to be observed, the polar cap of the neutron star must be directed toward the observer and, at the same time, the lightning must be formed. The maximum burst rate is related to the time of the plasma outflow from the polar cap region. The typical interval between two consecutive bursts is ~100 s. The width of a single radio burst can be determined both by the width of the emission cone formed by the lightning emitting regions at some height above the neutron star surface and by a finite lightning lifetime. The width of the phase distribution for radio bursts from RRATs, along with the integrated pulse width, is determined by the width of the bundle of open magnetic field lines at the formation height of the radio emission. The results obtained are consistent with the currently available data and are indicative of a close connection between RRATs, intermittent pulsars, and extreme nullers.Comment: 24 pages, no figures, references update

Synthesis and investigation of highly transparent ceramics

A short review of research works carried out in the Institute of Electrophysics UrB RAS on the development of synthesis technology for laser ceramics and the analysis of their characteristics is presented. These ceramics are widely used as active media of solid-state lasers, transparent armor, envelopes of high intensity discharge lamps, heat-resistant and mechanically strong windows etc. © 2019 IOP Publishing Ltd. All rights reserved.Russian Foundation for Basic Research, RFBR: 17-08-00064 A.The reported study was funded by RFBR according to the research project No. 17-08-00064 A

Synthesis of Tb2 O3 nanoparticles by laser ablation in Ar gas flow

In this paper, we report on the synthesis of terbium sesquioxide (Tb2 O3 ) nanopowder by laser ablation of a solid target material in Ar gas flow using an ytterbium fiber laser with an average power of 300 W. The as-synthesized nanoparticles featured spherical morphology, an average size of 13 nm and a substantially monoclinic crystal structure, whose symmetry was converted into cubic by heat treatment at 850°C under vacuum. Pressureless densification of powder compact at 1450°C yields 95.6 % of the relative density indicating excellent sinterability of the produced nanoparticles. XPS analysis was used to estimate the ratio between O and Tb concentrations as [O] / [Tb] =1.51, which is close to the Tb2 O3 stoichiometry indicating a very low content of detrimental Tb4+ ions. The obtained results suggest that laser ablation in Ar gas flow is a promising technique for synthesizing Tb2 O3 nanoparticles suitable for further fabrication of advanced magnetooptical ceramics. © 2022, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.Russian Science Foundation, RSFAcknowledgements. The reported study was carried out with the use of grant № 22‑23‑00658 of the Russian Science Foundation, https://rscf.ru/en/project/22‑23‑00658

Laser Ablation Synthesis and Characteristics of Tm-Doped Gd2O3 Nanoparticles

Synthesis of nano-sized particles of thulium-doped gadolinium sesquioxide is reported. The nanopowder was obtained by laser ablation of solid target composed of a mixture of Tm2O3 and Gd2O3 powders using radiation of pulse-periodical CO2 laser. Morphological features, structural characteristics of nanoparticles and their densification behavior were investigated. It was shown that the as-synthesized nanopowder consists of loosely agglomerated particles with spherical shape and a diameter from 10 to 40 nm. It was revealed that the obtained sample is in the form of solid solution of Tm2O3 in Gd2O3 with monoclinic crystalline phase exhibiting the following lattice parameters: a = 14.095 Å; b = 3.571 Å c = 8.758 Å β = 100.182 °. Using X-ray diffraction analysis it was determined that, as opposed to other rare-earth sesquioxides (for instance, Y2O3 and Lu2O3), the phase transformation of monoclinic modification into cubic modification was not observed under thermal treatment at a temperature up to 1200 °C. This was also confirmed by an absence of stepwise variation in density of Tm:Gd2O3 compact which was evident for Gd2O3 sample prepared from powder with cubic phase and micro-sized particles. © Published under licence by IOP Publishing Ltd.The reported study was funded by RFBR and Sverdlovsk region, project number 20-48-660039

Search for sterile neutrinos at the DANSS experiment

DANSS is a highly segmented 1~m${}^3$ plastic scintillator detector. Its 2500 one meter long scintillator strips have a Gd-loaded reflective cover. The DANSS detector is placed under an industrial 3.1~$\mathrm{GW_{th}}$ reactor of the Kalinin Nuclear Power Plant 350~km NW from Moscow. The distance to the core is varied on-line from 10.7~m to 12.7~m. The reactor building provides about 50~m water-equivalent shielding against the cosmic background. DANSS detects almost 5000 $\widetilde\nu_e$ per day at the closest position with the cosmic background less than 3$\%$. The inverse beta decay process is used to detect $\widetilde\nu_e$. Sterile neutrinos are searched for assuming the $4\nu$ model (3 active and 1 sterile $\nu$). The exclusion area in the $\Delta m_{14}^2,\sin^22\theta_{14}$ plane is obtained using a ratio of positron energy spectra collected at different distances. Therefore results do not depend on the shape and normalization of the reactor $\widetilde\nu_e$ spectrum, as well as on the detector efficiency. Results are based on 966 thousand antineutrino events collected at 3 distances from the reactor core. The excluded area covers a wide range of the sterile neutrino parameters up to $\sin^22\theta_{14}<0.01$ in the most sensitive region.Comment: 10 pages, 13 figures, version accepted for publicatio