Pub Date : 2022-04-24DOI: 10.3952/physics.v62i1.4697
L. Kazakevičiūtė-Jakučiūnienė, N. Tarasiuk, E. Maceika, R. Druteikienė, M. Konstantinova, Z. Žukauskaitė, R. Gvozdaitė, Š. Buivydas
Vertical distributions of 239,240Pu and 137Cs activity concentrations in the waterlogged and non-boggy soil cores sampled in the vicinity of Vilnius City and in the Varėna District were analyzed. The radionuclides appeared in the soils mainly as a result of the fallout after the nuclear weapon testing in atmosphere in 1960s and due to the Chernobyl NPP accident in 1986. The deposited radionuclides on the surface of waterlogged soils on the shores of lakes experienced processes of translocation and accumulation, therefore their total activity in the column differs from the activity in non-boggy soils. The mobility of plutonium is the highest in waterlogged organic-rich soils. Clay in the waterlogged soil significantly limits the migration of radiocesium and does not affect noticeably the mobility of plutonium. Compared with radiocesium, the mobility of plutonium in non-boggy soils is somewhat limited. So, in waterlogged and non-boggy soils, the radionuclide mobilizing factors act in the opposite directions for radiocesium and plutonium. A clear correlation between the radionuclide activity and soil organic matter content was not observed. The investigation showed that radionuclide mobility can be determined by studying radionuclide physicochemical forms in the soil, vertical profiles of radiocesium to plutonium ratios, soil composition as well as its oxidation regime.
{"title":"137Cs and 239,240Pu activity concentrations distribution in waterlogged and non-boggy soils of Lithuania","authors":"L. Kazakevičiūtė-Jakučiūnienė, N. Tarasiuk, E. Maceika, R. Druteikienė, M. Konstantinova, Z. Žukauskaitė, R. Gvozdaitė, Š. Buivydas","doi":"10.3952/physics.v62i1.4697","DOIUrl":"https://doi.org/10.3952/physics.v62i1.4697","url":null,"abstract":"Vertical distributions of 239,240Pu and 137Cs activity concentrations in the waterlogged and non-boggy soil cores sampled in the vicinity of Vilnius City and in the Varėna District were analyzed. The radionuclides appeared in the soils mainly as a result of the fallout after the nuclear weapon testing in atmosphere in 1960s and due to the Chernobyl NPP accident in 1986. The deposited radionuclides on the surface of waterlogged soils on the shores of lakes experienced processes of translocation and accumulation, therefore their total activity in the column differs from the activity in non-boggy soils. The mobility of plutonium is the highest in waterlogged organic-rich soils. Clay in the waterlogged soil significantly limits the migration of radiocesium and does not affect noticeably the mobility of plutonium. Compared with radiocesium, the mobility of plutonium in non-boggy soils is somewhat limited. So, in waterlogged and non-boggy soils, the radionuclide mobilizing factors act in the opposite directions for radiocesium and plutonium. A clear correlation between the radionuclide activity and soil organic matter content was not observed. The investigation showed that radionuclide mobility can be determined by studying radionuclide physicochemical forms in the soil, vertical profiles of radiocesium to plutonium ratios, soil composition as well as its oxidation regime.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48436368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-24DOI: 10.3952/physics.v62i1.4695
G. Stanionytė, V. Tamulienė, R. Grigonis, J. Vengelis
We report an experimental realization of a subnanosecond optical parametric amplifier (OPA) system in a beta barium borate (BBO) crystal pumped by the third harmonic of a passively Q-switched Nd:YAG microlaser system and seeded by the continuum generated in a photonic crystal fibre (PCF). It yields broadband continuous signal wavelength tunability in the visible spectrum range from 470 to 660 nm and the idler wavelength from 768 to 1450 nm. Besides the experimental data, the numerical simulation results of the BBO optical parametric amplifier are presented. The maximum output power of the subnanosecond BBO OPA is limited by laser induced damage in the BBO crystal by the pump radiation and seed radiation spectral power density. We also notice and discuss the effect of seed radiation on BBO OPA output radiation characteristics. The numerical simulations qualitatively agree with the experimental data.
{"title":"Investigation of a widely-tunable subnanosecond BBO-based optical parametric amplifier","authors":"G. Stanionytė, V. Tamulienė, R. Grigonis, J. Vengelis","doi":"10.3952/physics.v62i1.4695","DOIUrl":"https://doi.org/10.3952/physics.v62i1.4695","url":null,"abstract":"We report an experimental realization of a subnanosecond optical parametric amplifier (OPA) system in a beta barium borate (BBO) crystal pumped by the third harmonic of a passively Q-switched Nd:YAG microlaser system and seeded by the continuum generated in a photonic crystal fibre (PCF). It yields broadband continuous signal wavelength tunability in the visible spectrum range from 470 to 660 nm and the idler wavelength from 768 to 1450 nm. Besides the experimental data, the numerical simulation results of the BBO optical parametric amplifier are presented. The maximum output power of the subnanosecond BBO OPA is limited by laser induced damage in the BBO crystal by the pump radiation and seed radiation spectral power density. We also notice and discuss the effect of seed radiation on BBO OPA output radiation characteristics. The numerical simulations qualitatively agree with the experimental data.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45132062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-24DOI: 10.3952/physics.v62i1.4694
M. Berrehail, N. Benchiheub, S. Menouar, J. Choi
An approach to exact quantum solutions of the time-dependent two energy level Jaynes–Cummings model with an imaginary photon process is represented in this work. The Lewis–Riesenfeld invariant treatment and the unitary transformation method are used for this purpose. The original Schrödinger equation is reduced to an equivalent solvable one through unitary transformations by using suitable unitary operators. The reduced equation corresponds to a simpler Hamiltonian which is written as a linear combination of the generators of the reduced-dimensional SU(2) algebra. A Hermitian invariant operator is constructed based on the same algebraic formulation and its instantaneous eigenfunctions are obtained. By utilizing such eigenfunctions, the complete quantum wave functions of the system are evaluated. Such wave functions are necessary when we analyze the quantum characteristics of the system.
{"title":"Quantum Jaynes–Cummings model for a two-level system with effects of parametric time- dependences","authors":"M. Berrehail, N. Benchiheub, S. Menouar, J. Choi","doi":"10.3952/physics.v62i1.4694","DOIUrl":"https://doi.org/10.3952/physics.v62i1.4694","url":null,"abstract":"An approach to exact quantum solutions of the time-dependent two energy level Jaynes–Cummings model with an imaginary photon process is represented in this work. The Lewis–Riesenfeld invariant treatment and the unitary transformation method are used for this purpose. The original Schrödinger equation is reduced to an equivalent solvable one through unitary transformations by using suitable unitary operators. The reduced equation corresponds to a simpler Hamiltonian which is written as a linear combination of the generators of the reduced-dimensional SU(2) algebra. A Hermitian invariant operator is constructed based on the same algebraic formulation and its instantaneous eigenfunctions are obtained. By utilizing such eigenfunctions, the complete quantum wave functions of the system are evaluated. Such wave functions are necessary when we analyze the quantum characteristics of the system.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45249128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-04-24DOI: 10.3952/physics.v62i1.4698
A. Marsalka, A. Kalnaityte, T. Biekša, S. Bagdonas
There is a constant interest to increase the efficacy of photosensitized therapy by combining it with other modalities in order to boost the oxidative stress in tumour tissues, and L-ascorbic acid (AscA) could serve as a potential candidate. The photoinduced transformations of a hematoporphyrin-type photosensitizer (HpDiA) were chosen as a model system to monitor the effects of AscA on oxygen-dependent photoreactions in aqueous model solutions of different pH. Additional data on the role of the ascorbate radical in photoreactions initiated by HpDiA, as well as on the mutual activity in samples containing bovine serum albumin (BSA), including participation in Type I reactions, were obtained performing electron paramagnetic resonance (EPR) spectroscopy measurements, done on the mixed aqueous solutions poured into capillary tubes of a carefully selected diameter, both in the dark and under illumination with a laser beam in the absence of additional trapping molecules. A strong interaction between BSA and porphyrins was determined as a main factor in the observed photoreactions, not only boosting the photooxidation and photoreduction pathways, but also leading to the enhanced photoactivity in combination with AscA, especially, in the acidic medium.
{"title":"The combined effects of ascorbic acid and bovine serum albumin on phototransformations of hematoporphyrin derivative in aquaeous medium: Absorption and EPR spectroscopy study","authors":"A. Marsalka, A. Kalnaityte, T. Biekša, S. Bagdonas","doi":"10.3952/physics.v62i1.4698","DOIUrl":"https://doi.org/10.3952/physics.v62i1.4698","url":null,"abstract":"There is a constant interest to increase the efficacy of photosensitized therapy by combining it with other modalities in order to boost the oxidative stress in tumour tissues, and L-ascorbic acid (AscA) could serve as a potential candidate. The photoinduced transformations of a hematoporphyrin-type photosensitizer (HpDiA) were chosen as a model system to monitor the effects of AscA on oxygen-dependent photoreactions in aqueous model solutions of different pH. Additional data on the role of the ascorbate radical in photoreactions initiated by HpDiA, as well as on the mutual activity in samples containing bovine serum albumin (BSA), including participation in Type I reactions, were obtained performing electron paramagnetic resonance (EPR) spectroscopy measurements, done on the mixed aqueous solutions poured into capillary tubes of a carefully selected diameter, both in the dark and under illumination with a laser beam in the absence of additional trapping molecules. A strong interaction between BSA and porphyrins was determined as a main factor in the observed photoreactions, not only boosting the photooxidation and photoreduction pathways, but also leading to the enhanced photoactivity in combination with AscA, especially, in the acidic medium.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44674810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-17DOI: 10.3952/physics.v62i1.4645
R. Mokrik, V. Samalavičius
The anomalous isotope-hydrogeochemistry phenomena in the groundwater of Estonian Cambrian-Vendian (Ediacaran) and Ordovician-Cambrian aquifer systems were formed in the Late-Middle Pleistocene. In the periglacial environment, in northern and northwestern Estonia, these aquifer systems with fracture porose crystalline basement are connected to hydraulically joint unit characterized by high radioactivity groundwater. A significant alteration of groundwater occurred by series of isotope and chemistry facies fractionation. In this study, uranium isotopes activity ratio (234U/238U), 4He content, isotope-hydrogeochemistry and adjusted 14C ages are coupled for a new prospect of the estimation of northern Baltic Basin groundwater evolution. Analyzing radiocarbon and 4He groundwater residence time results and uranium isotope activity ratio distribution suggests a prolonged periglacial environment in which groundwater evolved. Stable isotope ratios of δ18O and δ2H correlation and hydrochemical composition changes support the cryogenic origin of groundwater. Pleistocene glaciations cyclically affect groundwater in multiple ways: permafrost isotope-geochemistry partitioning; periodically changing reversed flow directions of recharge and discharge areas; oscillations of the sea, river system, and periglacial lakes level, surface and sub-permafrost water mixing via taliks and fractured basement rocks. These processes lead to forming the sequence of isotope-hydrogeochemistry types and specific zoning; in general, two separate groundwater fractions – brackish in the lower part and freshened above. An extensive groundwater exploitation on the northern coast sites influenced a sharp dysfunction in the groundwater body, destabilizing the natural equilibrium state formed in the Holocene and Pleistocene.
{"title":"Interpretation of the anomalous groundwater chemistry and 234u/238u activity ratio disequilibrium in the northern part of the baltic region","authors":"R. Mokrik, V. Samalavičius","doi":"10.3952/physics.v62i1.4645","DOIUrl":"https://doi.org/10.3952/physics.v62i1.4645","url":null,"abstract":"The anomalous isotope-hydrogeochemistry phenomena in the groundwater of Estonian Cambrian-Vendian (Ediacaran) and Ordovician-Cambrian aquifer systems were formed in the Late-Middle Pleistocene. In the periglacial environment, in northern and northwestern Estonia, these aquifer systems with fracture porose crystalline basement are connected to hydraulically joint unit characterized by high radioactivity groundwater. A significant alteration of groundwater occurred by series of isotope and chemistry facies fractionation. In this study, uranium isotopes activity ratio (234U/238U), 4He content, isotope-hydrogeochemistry and adjusted 14C ages are coupled for a new prospect of the estimation of northern Baltic Basin groundwater evolution. Analyzing radiocarbon and 4He groundwater residence time results and uranium isotope activity ratio distribution suggests a prolonged periglacial environment in which groundwater evolved. Stable isotope ratios of δ18O and δ2H correlation and hydrochemical composition changes support the cryogenic origin of groundwater. Pleistocene glaciations cyclically affect groundwater in multiple ways: permafrost isotope-geochemistry partitioning; periodically changing reversed flow directions of recharge and discharge areas; oscillations of the sea, river system, and periglacial lakes level, surface and sub-permafrost water mixing via taliks and fractured basement rocks. These processes lead to forming the sequence of isotope-hydrogeochemistry types and specific zoning; in general, two separate groundwater fractions – brackish in the lower part and freshened above. An extensive groundwater exploitation on the northern coast sites influenced a sharp dysfunction in the groundwater body, destabilizing the natural equilibrium state formed in the Holocene and Pleistocene.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":"1 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70032707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-03DOI: 10.3952/physics.v61i4.4639
G. Žlabys, M. Račiūnas, E. Anisimovas
Keywords: feedforward autoencoder, low-dimensional Hilbert spaces, numerical ground-state estimation We study the applicability of feedforward autoencoders in determining the ground state of a quantum system from a noisy signal provided in a form of random superpositions sampled from a low-dimensional subspace of the system’s Hilbert space. The proposed scheme relies on a minimum set of assumptions: the presence of a finite number of orthogonal states in the samples and a weak statistical dominance of the targeted ground state. The provided data is compressed into a two-dimensional feature space and subsequently analyzed to determine the optimal approximation to the true ground state. The scheme is applicable to single- and many-particle quantum systems as well as in the presence of magnetic frustration.
{"title":"Autoencoder-aided analysis of low-dimensional Hilbert spaces","authors":"G. Žlabys, M. Račiūnas, E. Anisimovas","doi":"10.3952/physics.v61i4.4639","DOIUrl":"https://doi.org/10.3952/physics.v61i4.4639","url":null,"abstract":"Keywords: feedforward autoencoder, low-dimensional Hilbert spaces, numerical ground-state estimation \u0000We study the applicability of feedforward autoencoders in determining the ground state of a quantum system from a noisy signal provided in a form of random superpositions sampled from a low-dimensional subspace of the system’s Hilbert space. The proposed scheme relies on a minimum set of assumptions: the presence of a finite number of orthogonal states in the samples and a weak statistical dominance of the targeted ground state. The provided data is compressed into a two-dimensional feature space and subsequently analyzed to determine the optimal approximation to the true ground state. The scheme is applicable to single- and many-particle quantum systems as well as in the presence of magnetic frustration.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47163877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-03DOI: 10.3952/physics.v61i4.4641
L. Veselis, R. Burokas, A. Michailovas
Keywords: solid-state amplifier, thermal effects, depolarization In this work, a double-pass end-pumped Yb:YAG amplifier system was investigated experimentally and numerically. The amplifier was seeded by a fibre-CPA based seed laser FemtoLux 30 (Ekspla). The presented laser system produced 129 W average power and 129 μJ energy pulses at 1 MHz pulse repetition rate, with optical-to-optical efficiency of 32% at room temperature (T = 20°C). The resulting beam quality was M2 ∼ 2.1 and the measured depolarization losses were to 17.9%. After the compression, 441 fs pulse duration was achieved. During the work, comprehensive amplifier modelling was performed using the code written in Matlab. The modelling results matched well the experimental data, providing the tool to predict the performance of laser systems based on ytterbium-doped isotropic crystalline, ceramic and glass laser materials prior to designing and manufacturing.
{"title":"Numerical model of end-pumped Yb:YAG double-pass laser amplifier experimentally validated at 129 W output power","authors":"L. Veselis, R. Burokas, A. Michailovas","doi":"10.3952/physics.v61i4.4641","DOIUrl":"https://doi.org/10.3952/physics.v61i4.4641","url":null,"abstract":"Keywords: solid-state amplifier, thermal effects, depolarization \u0000In this work, a double-pass end-pumped Yb:YAG amplifier system was investigated experimentally and numerically. The amplifier was seeded by a fibre-CPA based seed laser FemtoLux 30 (Ekspla). The presented laser system produced 129 W average power and 129 μJ energy pulses at 1 MHz pulse repetition rate, with optical-to-optical efficiency of 32% at room temperature (T = 20°C). The resulting beam quality was M2 ∼ 2.1 and the measured depolarization losses were to 17.9%. After the compression, 441 fs pulse duration was achieved. During the work, comprehensive amplifier modelling was performed using the code written in Matlab. The modelling results matched well the experimental data, providing the tool to predict the performance of laser systems based on ytterbium-doped isotropic crystalline, ceramic and glass laser materials prior to designing and manufacturing.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46332329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-03DOI: 10.3952/physics.v61i4.4643
E. Jakubovskij, A. Selskis, I. Ignatjev, G. Stalnionis, V. Šablinskas
Keywords: multi-walled carbon nanotubes (MWCNT), iridium-doped, nanohybrid composite, Raman spectrum, energy-dispersive X-ray spectroscopy Multi-walled carbon nanotubes have been prepared by chemical vapour deposition pyrolysis of ethyl alcohol at 665°C. The addition of atoms other than carbon to the nanostructure, in our case the iridium component, leads to the formation of defects that contribute to changes in the electrical and optoelectrical properties. The formation and structural changes of multi-walled nanotubes were studied using an electron microscope, Raman and energydisperse spectrometry. Using the Raman and X-ray spectrum, a clear difference between the synthesis without and with the addition of iridium impurities was found.
{"title":"Synthesis and characterization of iridium-doped multi-walled carbon nanotubes","authors":"E. Jakubovskij, A. Selskis, I. Ignatjev, G. Stalnionis, V. Šablinskas","doi":"10.3952/physics.v61i4.4643","DOIUrl":"https://doi.org/10.3952/physics.v61i4.4643","url":null,"abstract":"Keywords: multi-walled carbon nanotubes (MWCNT), iridium-doped, nanohybrid composite, Raman spectrum, energy-dispersive X-ray spectroscopy \u0000Multi-walled carbon nanotubes have been prepared by chemical vapour deposition pyrolysis of ethyl alcohol at 665°C. The addition of atoms other than carbon to the nanostructure, in our case the iridium component, leads to the formation of defects that contribute to changes in the electrical and optoelectrical properties. The formation and structural changes of multi-walled nanotubes were studied using an electron microscope, Raman and energydisperse spectrometry. Using the Raman and X-ray spectrum, a clear difference between the synthesis without and with the addition of iridium impurities was found.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2022-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43022946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-10-11DOI: 10.3952/physics.v61i3.4516
T. Akopdzhanyan, A. A. Kondakov, S. Rupasov, A. Kozlova, V. Pankratov
The synthesis method of aluminium oxynitride (AlON) powders by nitriding of Al/Al2O3 mixture under highpressure nitrogen is proposed. The novelty of this method consists in adding KClO4 or Mg(ClO4)2 and extra Al into the starting mixture (Al+Al2O3) to cause the exothermal aluminium oxidation reaction, which therefore initiates the aluminium nitriding reaction. The microstructure and phase composition of the AlON powders obtained by self-propagating high-temperature synthesis are demonstrated by means of SEM and XRD analysis. Diffuse reflection spectra of AlON powders have been measured and the values of band-gap energy have been calculated. Optical transmission and reflection characteristics of the AlON ceramic samples sintered from AlON powders at 1930°C have been studied. The influence of the technological parameters of ceramics production on their transparency is revealed – the most transparent sample is obtained from the powders synthesized with the Mg(ClO4)2 additive and sintered for 6 h.
{"title":"Optical properties of powder and ceramics of aluminium oxynitride obtained by self-propagating high-temperature synthesis","authors":"T. Akopdzhanyan, A. A. Kondakov, S. Rupasov, A. Kozlova, V. Pankratov","doi":"10.3952/physics.v61i3.4516","DOIUrl":"https://doi.org/10.3952/physics.v61i3.4516","url":null,"abstract":"The synthesis method of aluminium oxynitride (AlON) powders by nitriding of Al/Al2O3 mixture under highpressure nitrogen is proposed. The novelty of this method consists in adding KClO4 or Mg(ClO4)2 and extra Al into the starting mixture (Al+Al2O3) to cause the exothermal aluminium oxidation reaction, which therefore initiates the aluminium nitriding reaction. The microstructure and phase composition of the AlON powders obtained by self-propagating high-temperature synthesis are demonstrated by means of SEM and XRD analysis. Diffuse reflection spectra of AlON powders have been measured and the values of band-gap energy have been calculated. Optical transmission and reflection characteristics of the AlON ceramic samples sintered from AlON powders at 1930°C have been studied. The influence of the technological parameters of ceramics production on their transparency is revealed – the most transparent sample is obtained from the powders synthesized with the Mg(ClO4)2 additive and sintered for 6 h.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":"1 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2021-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46234626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-12DOI: 10.3952/PHYSICS.V61I1.4408
M. Konstantinova, D. Germanas, A. Gudelis, A. Plukis
The gamma-ray spectrometry by the instrumentality of Ge detectors is used for the detection of low activity environmental samples of different geometry (soil samples, air filters with aerosols, milk powder, etc.). Such measurements require separate calibration of the detector. The high purity germanium (HPGe) gamma-ray spectrometer of GC2520 series was used for experiments. For the efficiency calibration, three cylindrical containers filled with different 60Co water solution levels were used, and the gamma-ray coincidence summing was modelled using MCNP6. The dimensions of the pure germanium crystal, provided by Canberra, were used for the simulations. The true coincidence summing takes place when two or more gamma quanta, which are emitted in a cascade from an excited nucleus, are detected within the resolving time of the detector. However, there is often a mismatch between the simulated and experimental efficiencies. The experimentally obtained and modelled spectra were compared: a good consistency of experimental and modelled results allows investigating the volume sources. During the simulation it was found that the factors affecting the accuracy of modelling are the thickness of the dead layer, crystal dimensions and the thickness of the Al detector cap. The analysis allows measuring the radionuclides activity concentration of samples placed in the containers with different filling heights having only standard shape calibration sources. The obtained accuracy is sufficient to fulfil criteria of 5–10% for such type of simulation to be applied for measurements of real samples in standard BURK-60 containers of various sample filling heights.
{"title":"Efficiency calibration of high-purity germanium detector using Monte Carlo simulations including coincidence-summing corrections: volume source case","authors":"M. Konstantinova, D. Germanas, A. Gudelis, A. Plukis","doi":"10.3952/PHYSICS.V61I1.4408","DOIUrl":"https://doi.org/10.3952/PHYSICS.V61I1.4408","url":null,"abstract":"The gamma-ray spectrometry by the instrumentality of Ge detectors is used for the detection of low activity environmental samples of different geometry (soil samples, air filters with aerosols, milk powder, etc.). Such measurements require separate calibration of the detector. The high purity germanium (HPGe) gamma-ray spectrometer of GC2520 series was used for experiments. For the efficiency calibration, three cylindrical containers filled with different 60Co water solution levels were used, and the gamma-ray coincidence summing was modelled using MCNP6. The dimensions of the pure germanium crystal, provided by Canberra, were used for the simulations. The true coincidence summing takes place when two or more gamma quanta, which are emitted in a cascade from an excited nucleus, are detected within the resolving time of the detector. However, there is often a mismatch between the simulated and experimental efficiencies. The experimentally obtained and modelled spectra were compared: a good consistency of experimental and modelled results allows investigating the volume sources. During the simulation it was found that the factors affecting the accuracy of modelling are the thickness of the dead layer, crystal dimensions and the thickness of the Al detector cap. The analysis allows measuring the radionuclides activity concentration of samples placed in the containers with different filling heights having only standard shape calibration sources. The obtained accuracy is sufficient to fulfil criteria of 5–10% for such type of simulation to be applied for measurements of real samples in standard BURK-60 containers of various sample filling heights.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2021-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49458663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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