Vol 7, No 3 (2023)
139-147 530

Today one of the important problems of elementary particle and high energy physics is the study of strongly interacting matter under extreme conditions. In experiments with relativistic heavy ion reactions, a new phase of matter: quark-gluon plasma is being studied. It make possible to shed the light on the first seconds of the Universe existence, as well as to quantitatively describe the processes of neutron star merger. Ultra-high density nuclear matter states could be investigated in the collisions of heavy nuclei at energy range 4 - 11 GeV by studying of the particles yields which contained charm quarks in the Multi Purpose Detector experiment at the NICA collider. In this work, the concept of tracking detector was proposed together with the corresponding modeling of such detector whose inner layers consist of new generation large area thin (40 μm ) monolithic active pixel sensors, and whose outer layers are built of pixel sensors (50 μm ) currently used in high-energy physics experiments. The identification capability of a vertex detector that uses 40 μm and 50 μm thick pixel sensors was obtained. These data give the possibility to reconstruct the decays of D+ mesons produced in gold-gold collisions in the NICA complex.

148-154 538

This article presents the development of a cost-effective and efficient electronic module for silicon photodetectors (SiPM). The electronic module combines essential functionalities, such as a high voltage power supply, a preamplifier, and a signal comparator, into a compact circuit. A high voltage power supply with a range of 30 to 140 V provides a stable bias voltage with 0.01 V accuracy, while a preamplifier with 40 gain and 250 MHz bandwidth enables signal amplification necessary to extract weak signals. The comparator converts an analogue signal (higher than 8 mV) into TTL (transistor-transistor logic), which makes it easy to process and analyze with digital devices such as microcontrollers or make it possible to send signals over long distances by a cable. The module has been tested using an LYSO scintillator and a silicon photomultiplier (SiPM) called a micropixel avalanche photodiode (MAPD). It provides a more effective and efficient solution for reading out signals from SiPMs in a variety of applications, delivering reliable and accurate results in real-time.

155-165 440

We investigate the Coulomb breakup of the 11Be halo nuclei on a light (carbon) target within nonperturbative
time-dependent approach including the low-lying resonance 5/2+ of 11Be (E= 1.232 MeV). We had found considerable contribution of the low-lying resonances ( 5/2+ , 3/2 and 3/2+ ) to the breakup cross section of 11Be on a heavy (208Pb) target at our previous calculations. The developed computational scheme is extended to study the breakup of 11Be on a light target. This work is the initial step, where the convergence and accuracy of the computational scheme is tested.

166-174 486

This paper presents the results of model calculations of the structure of the Cu-Te system at low temperatures, as well as the results of a study of the structure and phase transitions of synthesized non-stoichiometric compounds of copper tellurides. For the first time, using the USPEX evolutionary algorithm, model computer calculations of the search for stable phases of copper tellurides Cu n Te m (n,m = 1÷10) were carried out. At temperature T = 0 K and pressure p = 1 atm. As stable structures, the compositions Cu5Te4, Cu3Te2, and Cu7Te4 were identified, which are indicated in the triclinic and monoclinic syngonies. Based on the study of the phase diagram, calorimetric measurements and X-ray diffraction studies of experimentally synthesized samples of copper telluride, it was found that the non-stoichiometric compositions Cu1.96Te, Cu1.85Te, Cu1.80Te and Cu1.75Te at room temperature are single-phase. The Cu1.85Te, Cu1.80Te, and Cu1.75Te compounds are described by hexagonal crystalline superstructures obtained on the basis of the Novotny phase for Cu2Te with different degrees of unit cell parameter multiplicity. Cu1.96Te at room temperature is indicated in an orthorhombic phase with lattice parameters that are also multiples of the unit cell parameters of the Novotny phase. At high temperatures, all compositions of Cu2−x Te (x=0.04, 0.15, 0.20, 0.25) transform into high-temperature disordered FCC structures that exist up to their melting point. It is shown that in these compounds the transition of a low-temperature hexagonal and orthorhombic structure to a high-temperature FCC phase occurs through a series of polymorphic phase transformations.

175-184 373

The paper presents experimental studies on the choice of an internal standard in order to correction the matrix effect that occurs when determining uranium in human urine by inductively coupled plasma mass spectrometry. Monoelemental standard solutions of Sc-45, Rh-103, In-115, Ir-193, Th-232 were used as internal standards. The levels of the decrease in the sensitivity of analytical signals of internal standards and uranium spikes under the influence of the matrix effect were determined. The ratio of the measured concentration of internal standards in the background solution of 5% nitric acid and in the matrix of the urine simulator was found compared to uranium. Based on this, empirical coefficients were calculated that characterize the difference in the matrix influence on analytical signals of the internal standard and uranium signals. Adjustment applied was verified according to the internal standard using calculated empirical coefficients and measured values of analytical signals of the internal standard in samples and in the background solution. Iridium was identified as the most suitable of the elements listed as an internal standard according to various criteria. Based on experimental results, a procedure was developed for measuring uranium in urine using iridium as an internal standard.

185-196 404

Radiative relaxations of electronic excitations - self-trapped excitons (STE) in regular lattice sites (intrinsic luminescence) and exciton-like formations (ELF) in the field of homologous cations (exciton-like luminescence). It has been found that the maximum effect of luminescence enhancement occurs upon uniaxial deformation along the <110> crystallographic direction (compared to <100>), which coincides with the direction of the self-trapped anion exciton (<110>) in the KBr crystal matrix. The exciton mechanism was estimated from the increase in the intensity of the intrinsic s(4, 42eV) - and p(2, 3eV) - luminescences of STE, and the enhancement of luminescence intensity of near-single Na+ (2.85 eV), pair ions Na+ , Na+ (3.1 eV) and Na+ Pb++ (3.4 eV)- centers - recombination mechanism of radiative relaxation of electronic excitations.

197-206 495

In this work, we investigated the effect of nanostructuring on the thermoelectric and thermal properties of nonstoichiometric solid splavs doped with copper sulfides with potassium. The synthesized alloys K0.01Cu1.96S, K0.02Cu1.95S, K0.03Cu1.94S, K0.04Cu1.93S, K0.05Cu1.94S are nanocomposite. The crystallite sizes of the synthesized powder, as estimated from the half-width of X-ray diffraction lines, range from 7 to 180 nm. Sample K0.01Cu1.96S is a mixture of phases consisting of chalcocite Cu2S (82%), jarleite Cu1.96S (12%), anilite Cu1.75S (6%). The composition of samples K0.02Cu1.95S and K0.03Cu1.94S includes the most common phases of copper sulfides - chalcocite Cu2S , jarleite Cu1.96S, digenite Cu1.80S. Samples K0.04Cu1.93S and K0.05Cu1.94S consist of jarleite Cu1.96S, digenite Cu1.80S and potassium copper sulfide KCu4S3 phases. In a practical sense, the extremely low thermal conductivity values (from 0.16 to 0.80 W/m · K) found in the range of 300–700 K for nanocomposite samples K0.02Cu1.95S and K0.03Cu1.94S are very favorable for achieving high thermoelectric figure of merit ZT material.

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ISSN 2522-9869 (Print)
ISSN 2616-8537 (Online)