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Mirzayev, M.N. ,
Nasri nasrabadi, M. ,
Tiep n.v., N. ,
Samedov o.a., O. ,
Moslemi-mehni, E. ,
Samadov s.f., S. Vacuum (0042207X) 238
This research investigates the microstructure and surface morphology of ZrC nanocrystals irradiated with gamma quanta at energy levels of 1.17 MeV and 1.33 MeV, with absorption doses of 1500 and 3000 kGy. A 60Co isotope served as the gamma radiation source, and experiments were conducted under normal atmospheric conditions at room temperature. Analysis techniques included Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM—ZEISS, ΣIGMA VP), and transmission electron microscopy (TEM—Talos F200i). Gamma radiation induced the formation of new functional groups, transformed chemical bonds, and created active oxide centers on ZrC crystal surfaces. SEM results indicated nanoparticle mobilization with increased radiation absorption doses, while TEM analyses revealed amorphous oxide layers and a particle size increase to 23.46 nm at 3000 kGy. © 2025 Elsevier Ltd
Physics of Particles and Nuclei Letters (15318567) 22(2)pp. 255-259
Abstract: The photofission which is very important for various nuclear applications involves the excitation and subsequent fission of a nucleus by photon absorption. This study explores the complexities of 237Np photofission, highlighting the critical roles of nuclear level density at saddle points and fission barrier parameters. Using advanced theoretical models and nuclear reaction codes, the research investigates the interplay between these factors and the photofission cross sections of 237Np. Theoretical results are compared with experimental data to deepen our understanding of photofission dynamics. © Pleiades Publishing, Ltd. 2025.
Samadov s.f., S. ,
Ismayilova n.a., ,
Tuyen l.a., ,
Nasri nasrabadi, M. ,
Trung n.v.m., ,
Tiep n.v., N. ,
Samedov o.a., O. ,
Mustafayev i.i., ,
Jabarov s.h., ,
Donkov a.a., Journal of the European Ceramic Society (1873619X) 45(13)
In this work, the evolution of defects in zirconium carbide (ZrC) nanocrystals under gamma irradiation was studied using both experimental and computational approaches. Positron Annihilation Spectroscopy (PAS) and Raman spectroscopy were used to characterize radiation-induced defects, structural changes, and vibrational modes in ZrC samples. Density Functional Theory (DFT) calculations revealed that the displacement damage in the ZrC lattice increased with irradiation dose, and the increase in defects led to a significant decrease in Young's modulus and to lower hardness. Irradiation at 3000 kGy enhances defect evolution by creating carbon vacancies that potentially combine with existing defects to form larger vacancy clusters. In the Raman spectra, a new peak due to Sp2 C-C was detected at 1795 cm−1 at an absorption dose of 3000 kGy. The intensity ratio of the ID/IG band decreased from 1.133 (initial) to 1.09 (3000 kGy), reflecting amorphization and the formation of an oxide layer. These findings provide a foundation for future investigations aimed at optimizing the radiation tolerance of ZrC-based materials for advanced nuclear applications. © 2025 Elsevier Ltd
Physics of Plasmas (1070664X) 32(5)
Inertial electrostatic confinement (IEC) is a method utilized to confine particles in fusion reactions. In an IEC device, ions are accelerated toward the center by an electric field created through the application of a potential difference between the anode and the cathode. This issue increases in ion density at the center and enhances the probability of collisions, thereby facilitating fusion reactions. Neutron production rate and the confinement time (CT) are the key parameters in an IEC device. Previous studies simulated the effects of various parameters, such as pressure, the number of cathode rings, and the dielectric thickness of the feed-stalk, on CT, comparing the results with experimental data. Results indicated that at low pressures, CT decreased due to asymmetry in the electric field caused by the feed-stalk. This study simulated the effect of an ion gun on CT and proposed adding a second feed-stalk opposite the first to reduce field asymmetry and improve CT at lower pressures. Simulations conducted at a pressure of 1 × 10 − 7 Torr and a voltage of −250 kV resulted in a CT of 14 570 μs, notably higher than previous findings, underscoring the beneficial influence of the second feed-stalk on the CT. © 2025 Author(s).
Radiation Physics and Chemistry (18790895) 229
In this work, the IECF device using the MCNPX code was simulated and parameters such as lethargy as well as cross-sections, changes in neutron flux and dosimetry and suitable multi-layer shields were studied. To secure the device from radiation hazards at different work intensities and in addition to the role of shielding, the role of producing materials such as lithium, the required simulations were done and the necessary shield thicknesses were determined. From the intensity of 106s−1 which is used for nuclear laboratories in universities up to neutron production 1012s−1 which is used for the BNCT method, an optimal shield thickness is required. For the first layer, a material with an average mass number was chosen to absorb the highest amount of energy and produce the lowest amount of gamma in inelastic scattering with fast neutrons. The produced gammas are also absorbed by concrete. For the thickness changes of different layers, in addition to measuring the remaining energies in the neutron flux, the cross-sections corresponding to those energies were also measured in order to calculate the required shield thicknesses for different powers of the device in different working conditions. After determining the type of different materials suitable for shielding, dosimetry was performed according to the ICRP60 standard and by making the necessary changes in the thickness of the layers, the neutron and gamma doses were reduced to the standard level. Also, the fluxes of thermal, epithermal and fast neutrons were measured in different shielding layers. Finally, for all calculated neutron production intensities, the necessary shielding thickness was determined for safe operation of the device. As a result of this study, by modifying and improving the method of determining the required thickness of the shield for different intensities, the smaller and more suitable thickness for the intensity of 109 s−1 was determined. This improvement and reduction in the thickness of the shield caused a reduction in the weight of the total shield and a reduction in the cost of shield construction while maintaining radiation safety according to ICRP60 standards. The idea of lithium production by IECF device using the materials of this shielding was simulated by MCNPX code. Boric acid was investigated and studied as a suitable material for lithium production. After performing the simulation and calculations, the amount of 1 Kg of lithium per month of device working for 8 h per day was obtained which is a valuable amount and it is possible to increase its production. © 2024
Waves in Random and Complex Media (discontinued) (17455049) 34(4)pp. 2555-2566
In this article, the test particle method is used in order to calculate the Cherenkov radiation of runaway electrons. We have applied the dielectric tensor for hot magnetized plasma to derive the wave frequency of Cherenkov radiation due to particle resonance with the warm electrostatic waves. The electric field from the Cherenkov radiation is numerically calculated to model the radiation reaction force as a correction to the Coulomb logarithm in the collisional drag force. Then, the behavior of the correction term in strongly and weakly magnetized regimes is investigated. It is shown that both magnetic field strength and the speed of runaway electrons significantly modify the correction term. © 2021 Informa UK Limited, trading as Taylor & Francis Group.
Physica Scripta (00318949) 99(1)
The nuclear level density parameter (NLDP) plays an important and crucial role in the most widely used phenomenological models that calculate the nuclear level density (NLD) based on the Fermi gas model (FGM). NLDP can be affected by various effects that have been ignored during the FGM calculations. The dependence of NLDP on excitation energy has been predicted by various references and using various relationships that are mainly tested and normalized at low energies by experimental data of low levels. In this research, using nuclear reaction codes and experimental data of the evaporation spectrum of heavy ion 32S + 74Ge reaction leading to 106Cd compound nucleus (CN) at high excitation energies, high energy behaviour of NLDP is investigated and compared with different relationship predictions. By calculating and reducing the contribution of non-equilibrium mechanisms, it is suggested that NLDP behaves increasing and then decreasing at high energies (almost Gaussian-like behavior), contrary to the predictions of all conventional energy-dependent NLDP relations. © 2023 IOP Publishing Ltd.
Nuclear Engineering and Technology (2234358X) 56(1)pp. 292-300
Kinetic simulations have been performed on an Inertial Electrostatic Confinement Fusion (IECF) device. These simulations were performed using the particle-in-cell (PIC) method to analyze the behavior of ions in an IEC device and the effects of some parameters on the Confinement Time (CT). CT is an essential factor that significantly contributes to the IEC's performance as a nuclear fusion device. Using the PIC method, the geometry of a two-grided device with variable grid radius, the number of cathode grid rings, variable pressure and different dielectric thickness for the feed stalk was simulated. In this research, with the development of previous works, the interaction of particles was simulated and compared with previous results. The simulation results are in good agreement with the previous results. In these simulations, it was found that with the increase of the dielectric thickness of the feed stalk, the electric field was weakened and as a result, the confinement time was reduced. On the other hand, with the increase of the cathode radius, the confinement time increased. Using the results, an IEC device can be designed with higher efficiency and more optimal CT for ions. © 2023 Korean Nuclear Society
International Journal of Modern Physics E (17936608) 33(11)
Accurate simulation of radiative capture reactions (RCRs) requires precise modeling of γ-ray strength functions (GSF). Various GSF models exist but need normalization based on experimental total radiative width (TRW) data. This study found that current normalization methods fail for neutron-induced RCRs in 238U and 233Th nuclei. In this regard, re-normalization values are proposed in order to improve model consistency at low energies. The standard Lorentzian (SLO) model fits experimental data best with minimal normalization. © 2024 World Scientific Publishing Company.
Journal of Physics G: Nuclear and Particle Physics (13616471) 50(5)
Nuclear level density (NLD) is calculated using the statistical partition function method for 58Ni. The microscopic recursive approach based on the realistic single particle levels schemes obtained from various nuclear potentials is used to remove various simplifying approximations and accurately determine the NLD. The effect of these approximations is determined by comparing the results of this method with the usual and common calculations of the Fermi gas model. It is shown that such a fully microscopic approach represents the NLD behavior according to the available experimental data. © 2023 IOP Publishing Ltd.
Radiation Physics And Engineering (26456397) 4(3)pp. 29-41
In this work, neutron and gamma shielding were simulated using MCNPX code for an inertial electrostatic confinement Fusion (IECF) device. In this regard, various properties of shields were investigated. Portland reinforced concrete was considered as the first layer. In addition to being effective in reducing the dosage of fast neutrons, concrete layer was also considerably effective in reducing the dose of gamma rays. As for the second and third layers, we opted for paraffin and boric acid based. These layers were chosen based on parameters such as lethargy, macroscopic slowing down power (MSDP), etc. in order to reduce the speed of epithermal neutrons and then absorb the thermal neutrons, thus reducing the transmitted neutron dosage as much as possible. A layer lead was used after these three layers of shielding to attenuate the gamma ray reaching this layer. In this study, a fusion source based on D-T fuel with homogeneous and isotropic radiation of neutrons was used and then dosimetry was performed for different parts. Afterwards, the thickness of the shielding layers was optimized in such a way that the neutron and gamma doses were reduced according to the standards. We found that it is possible to achieve safe neutron and gamma fluxes and doses by applying about 5 layers of 50 cm thickness. We compared the results of our study with the those of another study done on shielding for the IECF device, which were in good agreement. © 2023 by the journal.
Journal Of Medical Signals And Sensors (22287477) 12(2)pp. 171-175
The purpose of this study is to assess a rare case of fetal radiation absorbed dose here through 18 F-Fludeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in early pregnancy (5-week-old fetus). The fetal absorbed dose due to the radiation emitted from the mother's body, the fetus self-dose, and the dose received from CT were computed. The 35-year-old patient, weighing 85 kg, was injected with 370 MBq of 18 F-FDG. Imaging started at 1 h with CT acquisition followed by PET imaging. The photon and positron self-dose was calculated by applying the Monte Carlo (MC) GATE (GEANT 4 Application for Tomographic Emission) code. The volume of absorbed dose from the mother's body organs and the absorbed dose from the CT were added to the self-dose to obtain the final dose. The volume of self-dose obtained through MC simulation for the fetus was 3.3 × 10-2 mGy/MBq, of which 2.97 × 10-2 mGy/MBq was associated with positrons and 0.33 × 10-2 mGy/MBq was associated with photons. Biologically, the absorbed dose from CT, 7.3 mGy, had to be added to the total dose. The absorbed dose by the fetus during early pregnancy was higher than the standard value of 2.2 × 10-2 mGy/MBq (MIRD DER) because, during the examinations, the mother's bladder was full. This issue was a concern during updating standards. © 2022 Isfahan University of Medical Sciences(IUMS). All rights reserved.
International Journal of Environmental Health Engineering (22779183) 11(1)
Aim: Protection against nuclear radiation is one of the most important issues in nuclear technology and industries that use this technology. Among the types of radiation emitted from radioactive sources, neutron and gamma rays are among the most dangerous radiations due to lack of electrical charge and serious damage to living tissues. The principal challenge in radiation protection is the proper design of a shield against neutron and gamma radiations. Hence, this study has investigated the improvement of the protection against these radiations. Materials and Methods: This study is of applied-developmental and quantitative type. Calculations have been performed using the MCNPX code in this study, which is one of the strongest nuclear calculation codes. The data were analyzed using quantitative statistics and ORIGIN software (OriginLab company, 1992, Northampton, Massachusetts, USA). Results: Based on the results, utilizing the spherical geometry had a better performance to increase the neutron fluxes in comparison with the cylindrical and cubic geometries. Moreover, polyethylene with high density was selected as the best moderator. Ultimately, it was dealt with the comparison and selection of the best protection to minimize the produced gamma rays due to the absorption of neutrons in different materials used by the source and neutrons that run away from the outer surface of the source configuration. Conclusion: Using the composite sphere of paraffin and polyethylene with high density up to a radius of 12 cm and tungsten with a thickness of 1 cm was suggested as the final configuration for the aim of this study. In comparison to the no-protection mode, this protection is effective to 74% in reducing the neuron dosage and 55% in reducing the primary gamma-ray, while the mentioned protection is about 72%–73% effective in reducing the general dose. © 2022 International Journal of Environmental Health Engineering.
European Physical Journal A (1434601X) 58(7)
The possible existence of quasi-bound state in KK¯ NN with quantum numbers J= 0 and I= 0 on the basis of four-body Alt-Grassberger-Sandhas equations in the momentum representation was investigated. We constructed a separable representation for the subamplitudes in the [3+1] and [2+2] partitions. The separable expansion for the integral kernels in the three- and four-body equations was obtained by using the method of the energy-dependent pole expansion (EDPE). Different separable phenomenological and chiral SU(3) based potentials having the one- and two-pole structure of the Λ(1405) resonance were used to study the dependence of the results on K¯ N- πΣ interaction. It was shown that the four-body KK¯ NN system is bound with a binding energy of BKK¯NN∼ 38–78 MeV and width of ΓKK¯NN= 46 - 118 MeV. © 2022, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Materials Chemistry and Physics (02540584) 271
In this work, molecular dynamics (MD) approach was performed in order to study the vacancy defect and temperature effects of GaN under Ar atomic bombardment (AB). In our computational study, the interatomic forces of nanostructures are based on Lennard-Jones and Tersoff force-fields. The results show that the vacancy defect of atomic structures is an important factor in AB procedure and the ideal matrix shows the maximum mechanical strength after Ar AB. In this structure, the final number of Ga and N atoms missing is smaller than defected matrix at T = 300 K. Furthermore, the effects of matrix temperature on dynamical manner of samples were investigated. MD calculations show that by temperature increasing from T = 300 K to T = 350 K, the GaN structure atom missing increases and so the atomic mechanical stability decreases in this procedure. Numerically, by a 50 K increase in the temperature of GaN atoms, the number of atoms missing in this structure increases by 54. © 2021 Elsevier B.V.
One of the most important characteristics of the IEC device is performing of advanced fusion reactions without radioactive products. In this work, the IEC device is simulated based on the primary conditions similar to the UW-IEC device with 3He as working gas using Particle in Cell (PIC) method for 7, 5, and 1.4 mA Ion Injection Currents (IICs). Once the different 3He plasma species have stabilized, the results show that on average, the number of ions inside the device and cathode increases by 67.5% and 57.3%, respectively, whereas the number of electrons increases just by 3%. The results show that nearly all the electrons in the device accumulate inside the cathode and the ions oscillate around the center of device. The obtained results show that the cathodic current for 1.4 mA IIC is comparable with that of measured by the UW-IEC device with 8% difference. The simulations also show 500 s−1 fusion reaction rates, which is very close to the measured value of 482 s−1. These results approve the validity of simulation. By calculating the electric field and potential, the number and exact location of nested virtual anodes and cathodes which are of important parameters for confinement quality are obtained. Also, this validated simulation could be used in future works in order to optimize the IEC device and its fusion reaction rate without any more experiments. © 2021
Physical Review C (24699985) 103(5)
Three-body calculations of the KK̄N system with quantum numbers I=1/2, Jπ=(12)+ were performed. Using separable potentials for two-body interactions, we calculated the πς mass spectra for the (K̄N)I=0+K+→(πς)0K+ reaction on the basis of the three-body Alt-Grassberger-Sandhas equations in the momentum representation. In this regard, different types of K̄N-πς potentials based on a phenomenological and chiral SU(3) approach were used. The possibility to observe the trace of the Λ(1405) resonance in the (πς)0 mass spectrum was studied. Using the χ2 fitting, it was shown that the mass of the Λ(1405) resonance is about 1417MeV/c2. © 2021 American Physical Society.
Journal of Materials Science (15734803) 55(10)pp. 4311-4320
Carbon nanotubes are one of the candidates for the reinforcement of metals for numerous applications. In this study, the effect of CNT on the primary radiation damage of CNT-Cu nanocomposite was investigated using molecular dynamics simulations. The simulations were performed by considering primary knock-on atom with 3 and 6 keV kinetic energies in the radial velocity direction (perpendicular to the cylinder axis) at various distances from the armchair CNT with (28, 28) chirality. Equivalent simulations in the single copper crystal and crystal containing cylindrical nanovoid (“CNV”) were performed for comparison. The results represent an improvement in radiation tolerance of copper composed with CNT nanofiller. In this material, CNT not only plays a sink role for point defects, but also it acts as a barrier to extend the displacement cascade. Some fluctuations in the number of the bulk vacancy around CNT-Cu interface were observed. The reason for this behavior was discussed. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
Iranian Journal of Physics Research (16826957) 20(3 Serial Number 81)pp. 57-63
At the present time, Magnetic Confinement Fusion (MCF) is considered as a way to produce energy. In this work, one of the Magnetohydrodynamic (MHD) limitations has been discussed. As closed magnetic surfaces, the Magnetic Islands (MIs) which are generated due to pressure effects, need to be surrounded by a separatrix which separate them from the other parts. External Magnetic Fields (EMFs), the safety factor (q) and the pressure profiles would be used to take the MIs under control. This could be achieved through an exterior medium, exclusively the Electron Cyclotron Heating (ECH) as well as the Current Drive (ECCD). Study of the magnetic flux surfaces and the effect of magnetic perturbation on tokamak plasmas, inform us about the formation of the MIs and their locations. In this work, together with the comprehensive review of the MIs and their importance, the conventional methods for improving the magnetic confinement has been introduced and discussed. In this regards, the Hot Limiter Biasing (HLB) method and the Resonant Helical Field (RHF) which is produced by external Helical Coils (HCs) were introduced and used. Then, the plasma current ( ), the Loop voltage, and the MO were obtained for different states. Finally, the Magnetic Islands Width (W) I p and their Growth Rate (GR) were calculated and compared with the experimental results. © 2020, Isfahan University of Technology. All rights reserved.
Physica A: Statistical Mechanics and its Applications (03784371) 558
In this paper, a kinetic method based on particle velocity distribution function in the context of the nonextensive Tsallis statistics is presented for ordinary and extraordinary waves in a collisionless magnetized hot plasma. The components of the generalized dielectric tensor for perpendicular propagation in hot nonextensive plasma are derived in terms of generalized hypergeometric functions. The components are expressed as functions of different values of the nonextensive parameter q, which quantifies the degree of nonextensivity of the system. The dispersion relations of ordinary and extraordinary waves in hot plasma are obtained in the context of the nonextensive statistics. It is shown that in hot nonextensive plasma the generalized dispersion relations of these waves depend on q parameter, which means that the initial distribution function alters the properties of ordinary and extraordinary waves. For the hot nonextensive plasma, the ordinary and extraordinary wave experience resonances at cyclotron harmonics, whilst the upper hybrid resonance is eliminated due to thermal effects. However, cutoff frequencies shift to higher values as q parameter increases. © 2020 Elsevier B.V.
Iranian Journal of Physics Research (16826957) 20(2)pp. 195-205
In this paper, by using the quantum input-output relations for an anisotropic slab, we investigate the quadrature squeezing and Mandel parameters of the transmitted squeezed coherent state through a metamaterial slab with negative refractive index and also a hyperbolic metamaterial slab. It will be shown that the nonclassical properties of the aforementioned state decrease sharply in passing through the negative refractive index slab. While, the hyperbolic metamaterial slab with a small absorption coefficient can somewhat retain the nonclassical properties of the incident squeezed light. © 2020, Isfahan University of Technology. All rights reserved.
International Journal Of Radiation Research (23223243) 17(4)pp. 651-657
Background: Clinical application of PET imaging for diagnosis, staging, re-staging treatment planning and treatment response assessment have become a major focus of studies in the past decades. Fetus is more sensitive to ionizing radiation, consequently, radiation absorption risks need to be assessed carefully. The objective of this article is to accurately estimate the absorbed dose during pregnancy in PET examinations. The method adopted in this article is simulative-analytic. Materials and Methods: The absorbed dose from administrating 18F-FDG during pregnancy is estimated through the BodyBuilder anthropomorphic mathematical phantom (inexpensive) together with Monte Carlo simulations in order to obtain a reliable and feasible methodology. In this simulation, the Specific Absorbed Fractions (SAF) is estimated for organs of 3, 6 and 9-months fetal. Results: The obtained results indicate that the absorbed dose of 18F-FDG PET imaging the fetal is 2.50×10-2 mGy/MBq early; 2.04×10-2 mGy/MBq first three months of pregnancy, 1.80 ×10-2 mGy/MBq second three months, and 1.50 ×10-2 mGy/MBq in the third three months of pregnancy. Maternal absorbed dose estimation here is (R2=0.965) which perfectly corresponds to ICRP publication. Conclusion: The results from Monte Carlo code with BodyBuilder anthropomorphic phantoms and ICRP recommendation are of acceptable correlation. Applying the pure BodyBuilder anthropomorphic phantoms in this simulation, which yields agreeable results in addition to its low time consumption, corresponds to the available finding by other researchers while reducing calculation times. Moreover, the fetal & maternal absorbed doses remain however well below the threshold for any deterministic effects. © 2019 Novin Medical Radiation Institute. All rights reserved.
Iranian Journal of Physics Research (16826957) 19(2)pp. 341-347
Nuclear level density is one of the most important concepts in nuclear physics; basically, it is the key in dealing with nuclear statistical problems. This quantity plays an essential role in the statistical calculation of reactor physics, astrophysics, researches in the average energy of heavy- ion collision and calculations related to neutron evaporation and other applications. This quantity can be calculated analytically by the partition function method and saddle point conditions. Nuclear level density parameter is an important parameter in the calculation of nuclear level density. In this study, this parameter was calculated according to the way in which the limited size of nucleus, continuous states, layer effects, temperature dependence of effective mass related to frequency and momentum and the change of these effects with temperature were considered. To this end, improved Thomas - Fermi approximation as a function of temperature was used. Also, by using this approximation, for continuous effects in the zero temperature, the nuclear level density parameter was calculated as a function of the mass number. . © 2019, Isfahan University of Technology. All rights reserved.
Journal of Instrumentation (17480221) 14(3)
The present work is related to the method for designing a driver for low pressure plasma sources using the AMPICP model. Particularly, it is related to equipment for producing plasma, which can be used for driver of the simulator project (ISTAPHM) of the interactions between ICRF antenna and plasma on Tokamak Nuclear Fusion Reactors. Here, two important aspects of this modeling are discussed: firstly, optimization of geometrical parameters for driver of source plasma in ISTAPHM and secondly, Simulation and computation of the EM fields adjusted for a planar antenna (PA) of driver. The work is focused on the characterization of low pressure Inductively Coupled Plasma (ICP) source and the features of a helicon chamber. Numerical simulations of ICP with PA were presented to optimize the plasma characteristics. The results of the AMPICP model for designing of ICP reactor as the driver in ISTAPHM were also evaluated using the power balance model. This paper also presents a two dimensional simulation for the EM field inside the ICP reactor for homogeneous plasma and compares the optimized and laboratory results with each other. From the measurements of the magnetic field inside the reactor using a magnetic probe, the electron number density and effective collision frequency can be estimated. The form of magnetic field lines inside the vessel was investigated and theoretical field lines were presented in the paper. The results of analyses as a function of operating parameters were presented to be measured with fixed and movable Langmuir probes. Optical Emission Spectra were recorded for different gas flow rates and filling pressures at constant power level by spectrometer. The variation in the intensity ratio of the selected emission lines, electron temperature and density was studied as a function of gas flow rate and filling pressure. © 2019 IOP Publishing Ltd and Sissa Medialab.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms (0168583X) 439pp. 43-50
In this research, in order to investigate primary radiation damage in iron nanofoam, simulation of displacement cascade near cylindrical nanovoids is performed using molecular dynamics. A primary knocked-on atom with 3, 6 and 9 keV energies and velocity parallel to the cylinder axis at 300 K is considered. 1–4 nanovoids are used as the model structure for free surfaces. It is identified that interaction between the displacement cascades and free surfaces is very sensitive to PKA energy and the distance of free surfaces. Near-surface cascade mechanism is observed when the displacement cascade interacts with a single cylindrical free surface, where clusters of bulk vacancies and a rim of adatoms are formed. In this case, based on the location of these defects rather free surface, two sub-mechanisms are identified. It is recognized that the degree of the penetration of the cascade into the cylindrical surfaces, plays an important role in forming vacancies and vacancy clusters in the ligament after the cooling of the cascade. Results show that when the PKA energy is 9 keV, enhancement of number of nanovoids increases the number of vacancies in the bulk. In this case, formation of vacancy planes is observed between the cylindrical nanovoids. The absorption of bulk vacancy clusters by the free surfaces is observed when displacement cascade is generated by a 6 keV PKA in close vicinity of four cylindrical surfaces. © 2018 Elsevier B.V.
Intermetallics (09669795) 104pp. 59-65
In this research, by employing DFT calculation and quasi-harmonic Debye model, the effect of composing element of CuNiCoFeV high entropy alloy on physical and thermal-elastic properties is investigated. In this regard, for an equimolar amount of CuNi, CuNiFe, CuNiCo, CuNiCoFe and CuNiCoFeV alloys with the face center cubic structure, parameters such as Wigner-Seitz radius, Curie temperature, volumetric thermal expansion coefficient, specific heat capacity, elastic constant and polycrystalline elastic moduli is calculated as a function of temperature. The effect of magnetic state of the mentioned equimolar alloys on these parameters is discussed. The results of thermal-elastic calculations show decreasing of elastic constants and polycrystalline elastic moduli such as the bulk modulus, shear modulus, Young's modulus and Poisson's ratio with increasing temperature from 0 K up to 600 K. These results predict the larger value of elastic constants, the bulk modulus, shear modulus and Young's modulus for equimolar alloys contain cobalt rather other present equimolar alloys. © 2018
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry (03645916) 66
In this research, the interaction between the composing elements of CuNiCoFe high entropy alloy with vacancies was investigated employing EMTO-LSGF and EMTO-CPA codes based on DFT calculations. In this regard, for the equimolar CuNiCo and CuNiCoFe alloys with the face center cubic structure, variation of vacancy formation energy was calculated as a function of the number of the nearest neighbors of composing elements. The results reveal that copper atoms have the strongest interaction with vacancy among all elements in both CuNiCo and CuNiCoFe equimolar alloys. The mean local vacancy formation energy () was calculated based on its distribution function for both alloys. Since the differences between the interaction energy of Cu-vacancy and other metal-vacancies in these two equimolar alloys was significant, to calculate the distribution function of vacancy formation energy and its dependence to temperature, equimolar CuNiCo and CuNiCoFe were estimated by a quasi-binary alloy. In this quasi-binary alloy copper is one of the components and other elements could be other components. The results show that of equimolar CuNiCoFe is 0.176 eV greater than that for CuNiCo equimolar alloy. The dependence of effective vacancy formation energy (E¯f) and renormalized vacancy formation energy (E˜f) to temperature is estimated using the single-site mean field approximations with energy parameters obtained in ab initio calculations. In these calculations, the alloy configurational entropy was used. The results indicate higher E¯f and E˜f values with increasing temperature from 400 to 2500K in both alloys. The values of E¯f and E˜f for CuNiCoFe are greater than those in CuNiCo within this range of temperature. © 2019 Elsevier Ltd
Radiation Physics and Chemistry (18790895) 152pp. 1-5
In the present research, polyvinyl butyral film was prepared and irradiated by gamma-ray at various doses up to 250 kGy. Then, the effects of irradiation on the PVB were studied through the tensile test, FTIR, 1H-NMR and AFM techniques. The results of tensile tests show the existence of ‘necking’ up to 100 kGy and an increase in the toughness up to 70 kGy. Structural study by spectroscopic techniques show the formation of new groups as a result of increased conjugated double bonds. At higher doses, however, the polymer began to decompose due to degradation of the main chains, which led to reduced mechanical strength. Finally, AFM examination of the samples revealed less rough surface by irradiation. © 2018 Elsevier Ltd
Journal of Environmental Radioactivity (18791700) 190pp. 66-72
The dynamic adsorption of xenon on molecular sieve packed columns was investigated. The modified Wheeler-Jonas equation was used to describe adsorption parameters such as adsorption capacity and adsorption rate coefficient. Different experimental conditions were accomplished to study their effects and to touch appropriate adsorbing circumstances. Respectable consistency was reached between experimental and modeled values. A purification and analysis setup was developed for radioactive xenon gas determination. Standard sample analysis results approved acceptable quantification accuracy. © 2018
Journal of Environmental Radioactivity (18791700) 182pp. 95-100
A xenon dynamic adsorption setup based on granular activated carbon packed column was developed. The adsorption behavior of xenon under different experimental conditions was studied and the results used to design an appropriate adsorber column for specific conditions. The resulting radioxenon gas extraction and quantification setup was evaluated based on an inter-comparison exercise and standard sample analysis results. The results showed that the quantification setup achieves experimental rules with uncertainty of ±3%. © 2017 Elsevier Ltd
International Journal Of Radiation Research (23223243) 15(4)pp. 383-390
Background: In CT systems, the machine utilizes a bowtie filter to shape the X -ray beam and remove lower energy photons. The shape of this bowtie filter is complicated and its geometry is o!en not available in detail. These renders the CT dose index (CTDI) to have different values in measurement versus Monte Carlo simulation studies and other analytical calculations especially in dosimetry of internal organs. In existing literature, the bowtie filter shape is extracted by using expensive sensors Materials and Methods: In the present work, the shape of the bowtie filter of the Biograph 6 PET/CT was derived by using Thermolumenecence dosimeters (TLDs). Subsequently, to evaluate the accuracy of the body bowtie filter shape as generated by TLDs, Monte Carlo simulation of CT was performed. 16 X-ray sources in various angles were used within the Monte Carlo code (MCNP-4C) to simulate the CT section of the PET -CT Biograph 6 system and to calculate dose. Results: The relative difference between simulated and measured CTDI value for the PET/CT Siemens Biograph 6 at 80, 110 and 130 kVp were 4.2, 2.9 and 2.3%, respectively. Conclusion: In this study, we demonstrate that it is possible to calculate the bowtie filter shape by using an inexpensive TLD method. The results showed that it is possible to determine the shape of the bowtie filter in PET/CT using TLDs with acceptable accuracy.
Journal of Instrumentation (17480221) 12(11)
This research aims to design and build a planar inductive coupled RF plasma source device which is the driver of the simulator project (ISTAPHM) of the interactions between ICRF Antenna and Plasma on tokamak by using the AMPICP model. For this purpose, a theoretical derivation of the distribution of the RF magnetic field in the plasma-filled reactor chamber is presented. An experimental investigation of the field distributions is described and Langmuir measurements are developed numerically. A comparison of theory and experiment provides an evaluation of plasma parameters in the planar ICP reactor. The objective of this study is to characterize the plasma produced by the source alone. We present the results of the first analysis of the plasma characteristics (plasma density, electron temperature, electron-ion collision frequency, particle fluxes and their velocities, stochastic frequency, skin depth and electron energy distribution functions) as function of the operating parameters (injected power, neutral pressure and magnetic field) as measured with fixed and movable Langmuir probes. The plasma is currently produced only by the planar ICP. The exact goal of these experiments is that the produced plasma by external source can exist as a plasma representative of the edge of tokamaks. © 2017 IOP Publishing Ltd and Sissa Medialab.
Radiation Measurements (13504487) 89pp. 14-22
In this study, lithium-tetraborate (LTB) was synthesized by three methods of high-temperature solid state, wet and combustion reactions. Copper was added to pure LTB by solution assisted method, to improve the thermoluminescence (TL) properties. The pellets of LTB were produced using pressing and sintering operations at 850 °C. The synthesized LTB pellets, exposed to the gamma radiation of 60Co source in the dose range of 5-20Gy and glow curves as well as dose-response diagrams were obtained. Ultimately, the effects of different factors on TL behaviors like dopant, crystallite size and particle morphologies were studied. The results show that between pure samples, LTB which synthesized by combustion method has higher TL sensitivity than those of other methods. However, it was seen a weak glow peak for 5Gy, due to the nanocrystalline structure of LTB. This property led to decrease TL intensity at low-doses and postponed saturation at high-doses. Fading of this sample was also less than others and has relatively better reproducibility. Among LTB:Cu pellets which synthesized by the wet reaction showed the higher TL response than others due to the creation of more traps and luminescence centers and had promising properties in the case of dose response linearity and fading. © 2016 Elsevier Ltd. All rights reserved.
Nuclear Engineering and Design (00295493) 296pp. 1-8
In this paper, a nonlinear controller using sliding mode method which is a robust nonlinear controller is designed to control a fast nuclear reactor. The reactor core is simulated based on the point kinetics equations and one delayed neutron group. Considering the limitations of the delayed neutron precursor density measurement, a sliding mode observer is designed to estimate it and finally a sliding mode control based on the sliding mode observer is presented. The stability analysis is given by means Lyapunov approach, thus the control system is guaranteed to be stable within a large range. Sliding Mode Control (SMC) is one of the robust and nonlinear methods which have several advantages such as robustness against matched external disturbances and parameter uncertainties. The employed method is easy to implement in practical applications and moreover, the sliding mode control exhibits the desired dynamic properties during the entire output-tracking process independent of perturbations. Simulation results are presented to demonstrate the effectiveness of the proposed controller in terms of performance, robustness and stability. © 2015 Elsevier B.V. All rights reserved.
Particulate Science and Technology (15480046) 34(5)pp. 533-539
In this paper the effects of flow rate, slurry solid content, and feed size distribution on the rod mill efficiency have been investigated. It is difficult to achieve highest grinding efficiency without sufficient information on operating parameters and their effects on the system. Several experiments were performed on a continuous rod milling circuit. Two flowsheets arrangements were considered to produce the particles with size <500 µm: an open circuit and a closed one. The flow rate selected at range of 11.5–17 t/h, slurry solid content at range of 27–61%, and feed size distribution at range of 12–30 mm. Results showed that the lowest grinding efficiency was occurred at solid content of 44 wt% and deviation from this optimum amount had positive implications on mill efficiency. Results also revealed an inverse relationship between flow rate and reduction ratio. The results of both open and closed circuits showed that the feed size had no effect on the mill product size (80% passing product size or d80). However, the reduction ratio was found to be sensitive to the feed size. Mathematical models were also developed to predict d80 and reduction ratio as a function of flow rate, solid content, and 80% passing feed size (f80). © 2016, Copyright © Taylor & Francis Group, LLC.
Journal of Process Control (09591524) 46pp. 84-91
Power control of the nuclear reactor is one of the most important subjects in each nuclear power plant. In this paper, a nonlinear controller using sliding mode method which is a robust nonlinear controller is designed to control a Traveling Wave Nuclear Reactor (TWR) power. The reactor core is simulated based on the point kinetics equations and six delayed neutron groups. Considering the limitations of the delayed neutron precursors densities measurement, a sliding mode observer is designed to estimate their values and finally a sliding mode control based on the sliding mode observer is presented to control the reactor core power. The stability analysis is given by means Lyapunov approach, thus the control system is guaranteed to be stable within a large range. Sliding Mode Control (SMC) is one of the robust and nonlinear methods which have several advantages such as robustness against matched external disturbances and parameter uncertainties. Since it has systematic design procedure, it is one of the most powerful solutions to design many practical control systems. The designed control system is evaluated in the presence of disturbances and uncertainties. The results show the robustness and performance of the used control system. © 2016 Elsevier Ltd
AIP Conference Proceedings (0094243X) 1653
Production of medical radioisotopes is one of the most important tasks in the field of nuclear technology. These radioactive isotopes are mainly produced through variety nuclear process. In this research, excitation functions and nuclear reaction mechanisms are studied for simulation of production of these radioisotopes in the TALYS, EMPIRE & LISE++ reaction codes, then parameters and different models of nuclear level density as one of the most important components in statistical reaction models are adjusted for optimum production of desired radioactive yields. © 2015 AIP Publishing LLC.
Acta Physica Polonica A (05874246) 127(4)pp. 961-964
Increased use of radiation in medicine, industry, and laboratories, requires safe conditions to be provided for its optimal use. One of the cases in which people are exposed to radiation, is during the detection of explosive materials by PGNAA method. Therefore, external dosimetry is necessary for workplaces where the method is used. In this study, Monte Carlo simulation program, MCNPX has been used to simulate gamma dose in the environment during the detection of explosive materials by PGNAA method. The simulated results were validated practically. The results indicate a good agreement between the simulated and measured data. The study demonstrated that MCNPX code can be used effectively for simulating gamma dose in various environments.
Physica Scripta (00318949) 90(12)
Phenomenological models that calculate the nuclear level densities (NLDs) based on the famous Fermi gas model are the most widely used models for practical applications, especially in nuclear reaction and evaporation codes. However, results of the most recent microscopic methods for calculation of NLDs indicate that the high-energy behavior of NLDs beyond approximately 30-50 MeV cannot be well described by these phenomenological models. In this research, using the results of microscopic spectral distribution method at high energies, a new relation for energy dependent NLD parameter is presented and using this new relation, these high-energy microscopic results and low energy experimental data can be well reproduced by Fermi gas phenomenological models. © 2015 The Royal Swedish Academy of Sciences.
Pramana - Journal of Physics (03044289) 85(1)pp. 149-159
In the present study, X-ray emission dose characteristics from a small Mather-type PF device in various pressures of argon as the operating gas were studied. The PF device was powered by a 12 μF capacitor at 25 kV charging voltage. Time-integrated hard X-ray (HXR) emission was investigated using thermoluminescence dosimeters (TLDs). These detectors were calibrated with 60Co and 131Cs sources. Twenty-four dosimeters were placed at four different radial distances from the axis of the electrodes at the top of the anode to measure the dose spatial distribution at the top of the anode for different pressures (0.5-1.3 mbar). At each radius, six dosimeters were placed circularly with equal angular intervals on the inner surface of the device chamber. It was found that the optimum pressure for the highest yield of X-ray is 0.9 mbar. The maximum measured dose was 17 mGy per shot at the top of the anode and about 0.5 mGy per shot at 90? with respect to the anode axis. Furthermore, these results showed that the dose at each radius is symmetrical at 360? around the top of the anode, but X-ray distribution follows an anisotropical behaviour. A fast plastic scintillator was also used for time-resolved HXR detection, and a linear relation was observed between the amplitude of the scintillator-PMT signals and TLD responses.
Annals of Nuclear Energy (03064549) 73pp. 496-499
The MCNP4c code, based on the probabilistic approach, is applied in modeling the 3D configuration of the Heavy Water Zero Power Reactors (HWZPRs) core. All of the constituents of the core such as fuel pellets, fuel elements, moderator (D2O) and annular graphite reflector are simulated using the MCNP4c code. The benchmark calculations are made to estimate various parameters including effective multiplication factor (Keff), number of neutron production per fission (ν), and energy release in the fuel per fission (Q). The (n,Xn) reaction with changes in water level are investigated. In order to validate the MCNP4c calculations, the obtained critical water level is compared to that of the experimental data. Good consistency is observed between calculated and experimental data. © 2014 Elsevier Ltd. All rights reserved.
Journal of Instrumentation (17480221) 9(9)
Validity of a virtual point detector model implying existence of a point where all interactions virtually occur was investigated for measuring the radioactivity of volume-ring sources. The dependency of the count rates on the distance between the virtual point detector and the detector surface for radioactive volume-ring sources with various radii was studied by MCNP4c simulations and the results were compared with the experimental data. Furthermore, the relationship between the virtual point detector and γ energy for the sources with various radii was investigated. © 2014 IOP Publishing Ltd and Sissa Medialab srl.
Journal of Fusion Energy (15729591) 33(6)pp. 746-751
Mass sweeping and current efficiency factors (fm and fi) are two important parameters in Z-pinch devices, because one can compute those to better analyze Z-pinch dynamics. In this paper, the advanced shock model was employed to calculate and compare the aforementioned parameters for ACOL Z-pinch in three different working regimes. It was found that fm is in the range of 0.12–0.13 for hydrogen gas at p0 = 400 and 800 Pa pressures and fm = 0.13 for helium gas at p0 = 260 Pa. Similar works have resulted fm in the range 0.10–0.16. Therefore our computations of fm values (range 0.1–0.13) agree with the fm range, and it confirms our model. Therefore, the factors can be precisely being calculated using advanced shock model for various Z-pinch systems at different working regimes. © 2014, Springer Science+Business Media New York.
Acta Physica Polonica B (05874254) 45(9)pp. 1865-1874
Determination of accurate nuclear level densities is of crucial importance for a variety of nuclear physics aspects and its related technologies. Therefore, there have been many theoretical and experimental efforts to determine nuclear level densities for variety of nuclei. In this research, the effects of changing structure and collective excitations on some deformed nuclei with axial symmetry were studied using microscopic generalized superfluid model (MGSFM) and experimental data. It was shown that the experimental data can be reproduced by a level density formalism developed for nuclei with static deformation.
Annals of Nuclear Energy (03064549) 59pp. 47-52
Shielding design of an isotropic 241Am-Be neutron source is investigated by Monte Carlo simulation, using MCNPX code. The 241Am-Be is an intense neutron emitter that is readily encapsulated in compact, portable, sealed sources. In the present work, a compact shield is designed with considering different materials in terms of both moderating power and absorbing ability. This arrangement is consistent with safety requirements, cost limitations and material availability. After optimizing the moderator thickness by MCNP code, different materials for attenuating neutrons are examined. Then the moderator is fixed and the best shield configuration is chosen to minimize the equivalent dose outside the shield. For this purpose, MCNPX flux to dose conversion factors reused. Finally, proper sites are determined in order to achieve maximum thermal and fast neutron flux. This configuration enables us to use neutron flux of sites with different energy ranges for irradiating samples with exposing personnel under acceptable radiation level. © 2013 Elsevier Ltd. All rights reserved.
Khosravi, M. ,
Shahbazi-gahrouei, D. ,
Jabbari, K. ,
Nasri nasrabadi, M. ,
Baradaran-ghahfarokhi, M. ,
Siavashpour, Z. ,
Gheisari, R. ,
Amiri, B. Radiation Protection Dosimetry (17423406) 156(3)pp. 356-363
Dose escalation with high-energy X rays of medical linear accelerators (linacs) in radiotherapy offers several distinct advantages over the lower energy photons. However, owing to photoneutron reactions, interaction of high-energy photons (>8 MV) with various high-Z nuclei of the materials in the linac head components produces unavoidable neutrons. The aim of this study was to evaluate the photoneutron dose equivalent per unit therapeutic X-ray dose of 18 MV, GE Saturne 20 linac in the treatment room using Monte Carlo (MC) MCNP linac head full simulation as well as thermoluminescence dosemeter measurements. This machine is one of the old linac models manufactured by General Electric Company; however, it is widely used in the developing countries because of low cost and simple maintenance for radiotherapy applications. The results showed a significant photoneutron dose from Saturne 20 linac head components especially at distances near the linac head (<150 cm). Results of this work could be used in several applications, especially designing bunker and entrance door shielding against neutrons produced by photoneutron reactions in GE Saturne 20. However, a detailed cost optimisation for a specific room would require a dedicated calculation. © The Author 2013. Published by Oxford University Press. All rights reserved.
Journal of Radioanalytical and Nuclear Chemistry (15882780) 293(2)pp. 479-482
Multiple sclerosis (MS) is a neurological autoimmune disease in which the immune system attacks the central nervous system for unknown reasons and causes several damages to human body by demyelinating the nerve cells. One of the possible cause of this disease is the abnormality levels of some trace elements such as Br, Fe, Rb, Sb, As, and Zn in human body. This study attempts to measure the levels of four trace elements of Br, Fe, Rb, and Zn in the patients' blood samples and compare them with control samples from healthy individuals. It should be noted that the objectives set out partly met. According to the obtained results, the differences between the levels of Br, Fe, and Rb in patients' blood samples and control was not significant (P>0.05). However, the average level of Zn between samples and controls showed a significant difference (P<0.05). Therefore the lower level of Zn in blood is likely to be a major cause of MS emergence. Furthermore, by using the concentration level of Zn as indicator, it was revealed that the risk of MS infection rises as the number of pregnancies increase. © Akadémiai Kiadó, Budapest, Hungary 2012.
Iranian Journal of Physics Research (16826957) 12(1)pp. 67-75
Nuclear level density (NLD) is one of the properties of nuclei with widespread applications in astrophysics and nuclear medicine. Since there has been little experimental and theoretical research on the study of nuclei which are far from stability line, studying NLD for these nuclei is of crucial importance. Also, as NLD is an important input for nuclear research codes, hence studying the methods for calculation of this parameter is essential. Besides introducing various methods and models for calculating NLD for practical applications, we used exact spectra distribution (SPDM) for determining NLD of two neutron and proton enriched exotic nuclei with the same mass number.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (01689002) 659(1)pp. 378-382
Nuclear-based explosive detection methods can detect explosives by identifying their elemental components, especially nitrogen. Thermal neutron capture reactions have been used for detecting prompt gamma 10.8 MeV following radioactive neutron capture by 14N nuclei. We aimed to study the feasibility of using field-portable prompt gamma neutron activation analysis (PGNAA) along with improved nuclear equipment to detect and identify explosives, illicit substances or landmines. A 252Cf radio-isotopic source was embedded in a cylinder made of high-density polyethylene (HDPE) and the cylinder was then placed in another cylindrical container filled with water. Measurements were performed on high nitrogen content compounds such as melamine (C3H6N6). Melamine powder in a HDPE bottle was placed underneath the vessel containing water and the neutron source. Gamma rays were detected using two NaI(Tl) crystals. The results were simulated with MCNP4c code calculations. The theoretical calculations and experimental measurements were in good agreement indicating that this method can be used for detection of explosives and illicit drugs. © 2011 Elsevier B.V. All rights reserved.
Journal of Physics: Conference Series (17426588) 295(1)
In this study, the single-particle level densities are calculated by using the isospin dependent nuclear level density (NLD) formula. The calculations are performed using the experimental data for 28Al achieved from 27 Al(n, γ)28Al resonances. Considering the symmetry energy and parity corrections, the NLDs at the excitation energy, E=20MeV are calculated and the maximum possible isospin in the range from ground state up to this excitation energy is estimated. The first correction led to reduced level densities and the later resulted in decreased densities for some of the levels while increased densities for the others. It is observed that the maximum level density occurs for T=1 and at low energies for which the experimental data are available there is a good agreement between calculated and experimental data.
Nuclear Engineering and Design (00295493) 241(5)pp. 1459-1462
The MCNP4c code, based on the probabilistic approach, was used to simulate 3D configuration of the core of the heavy water zero power reactor (HWZPR). In present work, first, all of the constituents of the core such as fuel pellets, fuel element, moderator (D2O) and annular graphite reflector were modeled using MCNP4c code. Then calculations of axial and radial neutron fluxes were performed in three energy groups such as thermal (0-0.625 eV), epithermal (0.625-550 eV), and fast (0.550-20 MeV). The cadmium ratio was calculated as well and the neutron flux parameters such as extrapolated height (H e), extrapolated radius (Re) and physical center of the core (z0) were computed using cadmium ratio. Comparison of the neutron flux parameters with the experimental data showed that the MCNP4c model of the HWZPR was validated. © 2011 Elsevier B.V. All rights reserved.
Acta Physica Polonica B (05874254) 42(3-4)pp. 505-508
In the current study, the ratio of the nuclear level densities with odd and even parities for 58Fe were calculated and compared with those of 60Ni, using a microscopic-macroscopic computational method. It was shown that the level densities of odd and even parities for even-even nuclei are not equal at low energies. However, increasing excitation energy reduces the difference between odd and even parities and equality is gained gradually.
Nuclear Physics A (03759474) 834(1-4)
Determination of accurate nuclear level densities is of crucial importance for a variety of pure and applied nuclear physics. The density of accessible levels is calculated for 166Er nucleus using the microscopic theory of interacting fermions and is compared with experimental data. It is shown that the data can be reproduced by a level density formalism developed for nuclei with static deformation. Our results are in a good agreement with the experimental data obtained by the Oslo group. © 2010 Elsevier B.V. All rights reserved.
Applied Radiation and Isotopes (09698043) 67(7-8)pp. 1208-1212
In this paper bulk sample prompt gamma neutron activation analysis (BSPGNAA) was applied to aqueous sample analysis using a relative method. For elemental analysis of an unknown bulk sample, gamma self-shielding coefficient was required. Gamma self-shielding coefficient of unknown samples was estimated by an experimental method and also by MCNP code calculation. The proposed methodology can be used for the determination of the elemental concentration of unknown aqueous samples by BSPGNAA where knowledge of the gamma self-shielding within the sample volume is required. © 2009 Elsevier Ltd. All rights reserved.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms (0168583X) 263(2)pp. 473-476
In this work thermal neutron self-shielding in aqueous bulk samples containing neutron absorbing materials is studied using bulk sample prompt gamma neutron activation analysis (BSPGNAA) with the MCNP code. The code was used to perform three dimensional simulations of a neutron source, neutron detector and sample of various material compositions. The MCNP model was validated against experimental measurements of the neutron flux performed using a BF3 detector. Simulations were performed to predict thermal neutron self-shielding in aqueous bulk samples containing neutron absorbing solutes. In practice, the MCNP calculations are combined with experimental measurements of the relative thermal neutron flux over the sample's surface, with respect to a reference water sample, to derive the thermal neutron self-shielding within the sample. The proposed methodology can be used for the determination of the elemental concentration of unknown aqueous samples by BSPGNAA where knowledge of the average thermal neutron flux within the sample volume is required. © 2007 Elsevier B.V. All rights reserved.
Journal of Nuclear Science and Technology (18811248) 39pp. 828-830
Statistical scission model is applied to fission fragment angular distributions from heavy-ion induced Fission. Comparison of model calculations to experimental data on angular distributions for 11B, 12C and 14N on 209Bi system shows excellent agreement. It is shown that statistical scission model (SSM) predicts angular distributions in reasonable agreement with those measured for heavy-ion induced fission of some reaction systems where the fission barrier has vanished or is very small relative to the nuclear temperature. © 2014 Atomic Energy Society of Japan. All Rights Reserved.
Communications in Theoretical Physics (02536102) 37(4)pp. 457-460
The level densities of even-odd and even-even isotopes 161,162Dy, 166Er and 171,172Yb were calculated using microscopic theory of interacting fermions and compared with experiments. It is found that the data can be well reproduced with level density formalism for nuclei with static deformation. The nuclear temperature as well as the entropy of nuclear system as a function of excitation energy has been extracted from the BCS theory. It is shown that the entropy exhibits an S-formed shape as a function of excitation energy. This is interpreted as a phase transition. Procedure of treating the even-odd and even-even nuclear systems has been presented and discussed.
Journal of Nuclear Science and Technology (18811248) 39pp. 826-827
The level densities of 162Dy, 166Er and 172Yb are calculated using the microscopic theory of interacting fermions and is compared with experiment. It is concluded that the data can be reproduced with level density formalism for nuclei with static deformation. © 2014 Atomic Energy Society of Japan. All Rights Reserved.
Communications in Theoretical Physics (02536102) 35(1)pp. 67-70
The excitation function for the fission of 230Th induced by neutrons has an unusual maximum for neutron energies in the vicinity of 700 KeV. It has been suggested that this maximum may be associated with the vibrational-mode resonance states. The unusual peak in the excitation function is interpreted in terms of a vibrational-mode resonance state in a two-humpted fission barrier. From theoretical fits to the fission cross sections and angular distributions, it is shown that the resonance has K = 1/2.
Physical Review C - Nuclear Physics (5562813) 63(6)pp. 646071-646075
The statistical scission model is applied to fission fragment angular distributions from heavy-ion induced reactions. It is shown that the statistical scission model predicts angular distributions in good agreement with those measured from heavy-ion induced fission of some reaction systems where the fission barrier has vanished or is very small relative to the nuclear temperature. The statistical variances extracted from these model calculations are compared with their corresponding values from a microscopic theory, which includes nuclear pairing interaction. It is found that the values of statistical variance S20 are very sensitive to the pairing energy. The effects of pairing interaction on the fragment angular distributions are illustrated and discussed.
