BULLETIN OF THE L.N. GUMILYOV EURASIAN NATIONAL UNIVERSITY. PHYSICS. ASTRONOMY SERIES

Thermal annealing of radiation-induced optical absorption of BaF2 and CaF2 crystals irradiated with fast xenon ions

2024-09-02T13:11:51+00:00

BaF₂ and CaF₂ crystals possessing high radiation resistance and as high-time resolution scintillators are used in high energy physics. In the present work, radiation defects in BaF₂ and CaF₂ crystals are investigated upon irradiation with 220 and 230 MeV ¹³²Xe ions to fluences of 10¹¹-10¹⁴ ions/cm². Optical absorption spectra were measured in the range from 10 to 1.5 eV. To study thermal annealing of the coloration centers created in BaF₂ and CaF₂ single crystals, step-by-step annealing of radiation defects was carried out. Multiple heating-cooling-measurement cycles were performed under identical conditions with increasing annealing temperature (T_ann) by 20-30 K. All spectra were measured at RT. It is assumed that the radiation-induced absorption band at 9.7 eV in CaF2 is made up of a combined contribution of anion clusters created in the ion track region and complex hole aggregates. The center responsible for the 8.15 eV band also has a hole nature and a structure close to the 6.5 eV center. In the UV region of the BaF₂ spectrum, a slight increase of the 9.18 eV band is observed in the temperature range 450-575K, which is accompanied by a decrease of the bands with maxima of 6.5 and 8.2 eV, i.e., the latter is also of hole nature. The bands 7.4 eV, 2.24 eV and 3.04 eV practically do not change in the whole annealing temperature range. By analogy with CaF2, in Xe-irradiated BaF2 single crystals, the high-energy bands below the fundamental absorption can also be of anion cluster nature.

AB-INITIO CALCULATIONS FOR THE SEARCH FOR STABLE STRUCTURES FOR IRON-PHOSPHORUS AND NICKEL-PHOSPHORUS SYSTEMS

2024-08-28T05:43:39+00:00

The study of the internal structure of our planet is one of the most relevant topics in fundamental research. In particular, the analysis of the phase ratios of iron compounds with light elements at high pressures is an important task for determining the composition and structure of the core of our planet. Due to the complexity of conducting experiments at such high pressures (in the Earth's core ~365 GPa), ab-initio calculations become a useful method for conducting such studies.

With the advent of new algorithms for searching for crystal structures, such as USPEX, AIRS and CALYPSO, the number of studies and available data on compounds of iron-nickel-containing systems with light elements has increased significantly. These tools have significantly expanded our capabilities in studying the internal processes in planets, creating broader prospects for further research and understanding the evolution of planetary bodies. The integration of these advanced computational methods makes it possible to accurately predict stable and metastable phases of iron compounds under extreme conditions, providing invaluable data on the behavior of materials in the conditions of the Earth's core.

Evaluation of uranium content in biological samples taken from residents of the village of Aksu, located near a radioactive waste storage facility

2024-09-05T08:12:39+00:00

The level of potential danger arising from radioactive waste storage facilities can be different. Studies are needed that allow us to draw conclusions about the impact of uranium discharged from waste storage facilities for local residents. The purpose of the work is to study the content of uranium in biological samples (urine, hair) taken from residents of the settlement of Aksu, located near the radioactive waste reservoir. During the study, the content of uranium was determined in biological samples taken from local residents living in the settlement of Aksu, located near the radioactive waste storage facility, with an average duration of 30 years. It was found that hair samples had a higher uranium content than urine samples. The data obtained can be used to determine the standard amount of uranium in the urine. At the same time, the detected uranium content in biological samples can be a bioindicator indicator in radiation safety measures.

DISTRIBUTION OF ALPHA PARTICLE TRACKS ON CR-39 DETECTOR IN RADON DIFFUSION CHAMBER

2024-09-02T04:32:23+00:00

The purpose of this study was to study the spatial distribution of traces of alpha particles formed by radon and its descendants in the diffusion chambers of radon. Three cylindrical chambers equipped with CR-39 detectors were used, the radon concentration was estimated using the RAD7 device. Registration revealed an uneven distribution of traces of alpha particles on the surface of the detector, the density of traces near the camera walls was 30% lower than in the center. These results were the opposite of analytical predictions based on the same camera dimensions. The critical angle of detection relative to the particle incidence energy was determined using the Track_vision software, which showed a significant effect of camera size and critical angle on the distribution of track density. In addition, the study examined the sources of changes in track density by analyzing partial contributions of volumetric and sedimentary fractions of radon and its descendants. There was an increase in the sidewall share, and with an increase in the radial distance from the detector Center, the volume and platform share decreased. Changing the dimensions of the camera affected the relative effects of these partial contributions, resulting in different distributions of visible traces on the detector's surface. The experimental results were compared with the values obtained using previously developed software based on the Monte Carlo method. Five different expressions of the detector response function were used, two of which greatly underestimated the results of the experiment. This comprehensive study sheds light on the complex dynamics of alpha particle propagation paths in radon diffusion chambers and highlights the importance of accurate modeling for reliable estimation of radon concentrations.

Study of the structural degradation kinetics of the near-surface layer of ZrO2 ceramics exposed to low-energy Не2+ ion irradiation

2024-09-05T03:02:22+00:00

The effects of radiation damage accumulation in the near-surface layer of ZrO₂ ceramics arising under high-dose irradiation with low-energy Не²⁺ ions alongside the determination of the influence of irradiation temperature on the thickness of the damaged layer in ceramics, the change of which is caused by the effects of ion diffusion into the depth of the material, are considered in this work. To determine the effects of radiation damage, and to determine the kinetics of changes depending on the variation of external factors, the method of Raman piezospectroscopy of lateral chips of ceramics was used, which made it possible to obtain data on changes in the values of residual stresses and FWHM along the trajectory of ion movement in the material, as well as at a depth exceeding the depth of ion penetration into the material. According to the conducted studies, it was established that the main type of deformation distortions arising as a result of irradiation and, as a consequence, the accumulation of structural changes caused by irradiation, is associated with the formation of residual mechanical tensile stresses in the structure. Moreover, a change in the irradiation conditions, in particular, an increase in the irradiation temperature, leads to an increase in the values of residual mechanical stresses in the structure of the damaged layer, and an increase in the thickness of the damaged layer is also observed, the change of which is due to the effects of ion diffusion deep into the target material. Analysis of alterations in the FWHM value indicates that at low irradiation fluences (below 10¹⁷ ion/cm²), the main changes in the structural features of the damaged layer are due to the effects of accumulation of structural distortions as a result of deformation stresses, while at high-dose irradiation, the formation of amorphous-like inclusions, the presence of which is associated with helium agglomeration, as well as the formation of gas-filled inclusions in the damaged layer, contribute to the destructive disordering of the damaged layer.

Multichannel coincidence analyzer for light charged particle identification

2024-09-02T18:14:43+00:00

Nuclear physics experiments use specially designed modular units that process signals from radiation detectors and provide information on the nature of these processes. These units, called nuclear electronics, form the basis of nuclear spectrometry systems in medicine, dosimetry, cosmic ray research, and other sources of ionizing radiation.

Rapid development in microelectronics over the past decade has had a significant impact on the development of nuclear electronics. Instead of many bulky modules, it is possible to implement compact integrated circuits for special purposes with digital signal processing or microcontroller systems with a built-in ADC in conjunction with a peak detector.

The article describes the creation of an electrical measurement circuit for the ΔE-E method of recording and identifying lightly charged particles using the MultiSim program. Using this program, a spectrometric amplifier, a single-channel analyzer, and a coincidence circuit were simulated using modern microelectronic components. Based on the simulated circuit, a prototype of a spectrometric amplifier was created. The signal obtained from the created prototype coincides with the simulated one. The obtained data indicate that the simulated scheme can be used for experiments in nuclear physics for the identification of lightly charged particles, as well as in other areas where there is a need for nuclear spectroscopy.

Surface modification of (DS) coatings based on Ni-Cr-Al by pulsed plasma treatment (PPT) method

2024-08-28T18:17:56+00:00

To safeguard materials against abrasive corrosion, various thermal spraying techniques can be employed, including powder spraying with a gas flame, plasma spraying, deposition and melting, high-speed oxygen-gas spraying, and detonation spraying. Thermal spraying is highly effective for protecting materials from wear and corrosion, thus extending their service life. This article discusses the changes in the surface of Ni-Cr-Al coatings subjected to pulsed plasma treatment using a plasma generator. The coatings were initially applied via detonation spraying (DS) and then underwent pulsed plasma treatment (PPT). The study investigates alterations in the structural and phase states of the coatings under plasma exposure. A comprehensive analysis of the detonation Ni-Cr-Al coatings' characteristics was conducted using scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDX), X-ray diffraction (XRD), surface roughness measurements, hardness tests, and tribological assessments. The findings indicate that pulsed plasma treatment enhances the wear resistance of the coatings' surface layer by reducing the coefficient of friction and increasing microhardness. X-ray phase analysis reveals that the improved tribomechanical properties of the treated surfaces are linked to an increased presence of CrNi₃, NiAl, and NiCr phases in the coatings.

Reanalysis of 20Ne + 24Mg elastic scattering angular distributions within various interaction potentials

2024-08-29T19:05:18+00:00

The angular distributions (ADs) for ²⁰Ne elastically scattered from a ²⁴Mg target were measured experimentally many years ago at E_lab = 50–100 MeV. Unfortunately, these data received little attention and were analyzed only from a phenomenological perspective at that time. This work is essentially devoted to investigating these data from a microscopic point of view, with a special interest given to the probable α + ¹⁶O cluster structure of the ²⁰Ne nucleus. The considered data are fairly well reproduced by the various implemented potentials. The study demonstrated the success of the proposed α + ¹⁶O cluster model of the ²⁰Ne nucleus in reproducing the considered ²⁰Ne + ²⁴Mg ADs over a wide range of energies.