arXiv subjects

Ahmet Ilker Topuz

Publications and source records attributed to Ahmet Ilker Topuz.

14 recordsLinked to original sources

arXiv2024

Unveiling secondary particle generation in a SONTRAC detector through GEANT4 simulations

SOlar Neutron TRACking (SONTRAC) is a detector concept based on a bundle of plastic scintillators by aiming at tracking the solar neutrons through the generation of the secondary particles such as protons from the (n, np) and (n, p) processes. In this study, in addition to the particle population, the energy spectra of the secondary particles including protons, gamma rays, electrons, alphas, and ions that are produced either due to the interaction between the fast neutrons and a SONTRAC detector or through the interplay between the secondary particles and the detector components are determined by means of GEANT4 simulations. The detector geometry in the present study consists of 34$\times$34 Kuraray Y11-200(M) fibers, and the current fiber bundle is irradiated with a planar vertical neutron beam of 0.2$\times$0.2 cm$^{2}$ by using an energy list composed of 20, 40, 60, 80, and 100 MeV where the number of incident neutrons is $10^5$. First, It is revealed that a non-negligible number of secondary protons are generated by the fast neutron bombardment; however, the population of these secondary protons is still low compared to the incident beam, i.e. in the order of $10^3$. Secondly, it is also observed that the energy spectrum of secondary protons exhibits a decreasing trend that is limited by the kinetic energy of incident neutrons. Additionally, the range of the secondary protons along with the deposited energy is computed, and it is demonstrated that a significant portion of the generated protons lose their entire energy and stop within the present SONTRAC detector. Finally, a 34$\times$34 pixel grid detector is introduced on each side of the fiber bundle to collect the optical photons produced from the energy deposition in the scintillation fibers, and the trajectory of the secondary protons on the pixel grid is shown by using a fast neutron beam of 100 MeV.

physics.ins-det↗

arXiv2024

Effect of hydrogen on albedo neutrons in lunar surface: A computational investigation by means of GEANT4 simulations

Motivated by the interaction of the cosmic ray protons with the lunar surface in the absence and presence of hydrogen, a series of GEANT4 simulations are employed in the current study to unveil the influence of hydrogen on the energy spectrum of the albedo neutrons that escape from the lunar surface. Initially, a discrete 69-bin proton energy spectrum between 0.4 and 115 GeV based on the PAMELA spectrometer is implemented into GEANT4. Subsequently, a single-volume lunar surface of 2-m thickness is constructed where it is assumed that a single layer of either 1.6 or 1.93 g/cm$^{3}$ constitutes the lunar regolith. The material composition in the present study includes 43.7 wt.$\%$ oxygen, 0.3 wt.$\%$ sodium, 5.6 wt.$\%$ magnesium, 9 wt.$\%$ aluminum, 21.1 wt.$\%$ silicon, 8.5 wt.$\%$ calcium, 1.5 wt.$\%$ titanium, 0.1 wt.$\%$ manganese, and 10.2 wt.$\%$ iron in accordance with another study. Then, 0.1 wt.$\%$ hydrogen is introduced by replacing oxygen in order to assess the impact of hydrogen on the secondary neutrons. In the wake of irradiating a lunar surface of 3$\times$2$\times$3 m$^{3}$ with a planar vertical PAMELA proton beam of 20$\times$20 cm$^{2}$, the depth profile of the generated neutrons as well as the corresponding initial energy spectrum is primarily obtained in the absence and presence of 0.1 wt.$\%$ hydrogen by voxelizing the entire geometry with 100 cells of 2-cm thickness. Next, a surface detector is placed at the top of the lunar surface in order to collect the albedo neutrons in both cases, and the energy spectra of the albedo neutrons are acquired in terms of thermal, epithermal, and fast neutrons. From the GEANT4 simulations in this study, it is shown that the presence of 0.1 wt.$\%$ hydrogen is observable in each energy regime of the albedo neutrons at the lunar surface, thereby providing an indication about the elemental variation of the lunar soil.

physics.ins-det↗

arXiv2024

COME: Cylindrical oriented muon emission in GEANT4 simulations

In this study, a source scheme based on source biasing as well as discrete energy spectrum in the cylindrical geometry is presented for the simulations of muon tomography in the GEANT4 toolkit. First, a lateral cylindrical surface and a top circular disc act as a generation surface that surrounds the tomographic setup. Then, the generated muons are directed towards the origin where the target volume is situated. Secondly, the kinetic energy of the entering muons is assigned by using a 80-bin discrete energy spectrum between 0 and 8 GeV that is extracted from the CRY muon generator. Thus, the present recipe is called cylindrical oriented muon emission (COME). This source scheme may especially find its applications in the cases where the lateral muon detectors are utilized in order to profit from the horizontal or horizontal-like muons.

physics.ins-det↗

arXiv2023

DOME: Discrete oriented muon emission in GEANT4 simulations

In this study, we exhibit a number elementary strategies that might be at disposal in diverse computational applications in the GEANT4 simulations with the purpose of hemispherical particle sources. To further detail, we initially generate random points on a spherical surface for a sphere of a practical radius by employing Gaussian distributions for the three components of the Cartesian coordinates, thereby obtaining a generating surface for the initial positions of the corresponding particles. Since we do not require the half bottom part of the produced spherical surface for our tomographic applications, we take the absolute value of the vertical component in the Cartesian coordinates by leading to a half-spherical shell, which is traditionally called a hemisphere. Last but not least, we direct the generated particles into the target material to be irradiated by favoring a selective momentum direction that is based on the vector construction between the random point on the hemispherical surface and the origin of the target material, hereby optimizing the particle loss through the source biasing. In the end, we incorporate our strategy by using G4ParticleGun in the GEANT4 code. Furthermore, we also exhibit a second scheme that is based on the coordinate transformation from the spherical coordinates to the Cartesian coordinates, thereby reducing the number of random number generators. While we plan to exert our strategy in the computational practices for muon scattering tomography, this source scheme might find its straightforward applications in different neighboring fields including but not limited to atmospheric sciences, space engineering, and astrophysics where a 3D particle source is a necessity for the modeling goals.

astro-ph.IM↗

arXiv2022

Applying triangular correlation of angular deviation in muon scattering tomography for multi-block materials via GEANT4 simulations

The scattering angle due to the target volume can be split into two interior angles in the tomographic setups based on the muon scattering, and we call this property as the triangular correlation where the sum of these two interior angles is equal to the scattering angle. In this study, we apply this triangular correlation for a multi-block material configuration that consist of concrete, stainless steel, and uranium. By changing the order of this material set, we employ the GEANT4 simulations and we show that the triangular correlation is valid in the multi-block material setups, thereby providing the possibility of supportive information for the coarse prediction of the material order in such configurations.

physics.ins-det↗

arXiv2022

Non-destructive interrogation of nuclear waste barrels through muon tomography: A Monte Carlo study based on dual-parameter analysis via GEANT4 simulations

In this study, we employ the Monte Carlo simulations by using the GEANT4 code to demonstrate the capability of muon tomography based on the dual-parameter analysis in the examination of the nuclear waste barrels. Our current hodoscope setup consists of three top and three bottom plastic scintillators made of polyvinyl toluene with the thickness of 0.4 cm, and the composite target material is a cylindrical nuclear waste drum with the height of 96 cm and the radius of 29.6 cm where the outermost layer is stainless steel with the lateral thickness of 3.2 cm and the filling material is ordinary concrete that encapsulates the nuclear materials of dimensions 20$\times$20$\times$20 cm$^{3}$. By simulating with a narrow planar muon beam of 1$\times$1 cm$^{2}$ over the uniform energy interval between 0.1 and 8 GeV, we determine the variation of the average scattering angle together with the standard deviation by utilizing a 0.5-GeV bin length, the counts of the scattering angle by using a 1-mrad step, and the number of the absorption events for the five prevalent nuclear materials starting from cobalt and ending in plutonium. Via the duo-parametric analysis that is founded on the scattering angle as well as the absorption in the present study, we show that the presence of the nuclear materials in the waste barrels is numerically visible in comparison with the concrete-filled waste drum without any nuclear material, and the muon tomography is capable of distinguishing these nuclear materials by coupling the information about the scattering angle and the number of absorption in the cases where one of these two parameters yields strong similarity for certain nuclear materials.

physics.ins-det↗

arXiv2022

Investigation of deflection angle for muon energy classification in muon scattering tomography via GEANT4 simulations

In muon scattering tomography, the investigated materials are discriminated according to the scattering angle that mainly depends on the atomic number, the density, and the thickness of the medium at a given energy value. The scattering angles at different initial energies also provide the opportunity to classify the incoming muons into a number of energy groups. In this study, by employing the GEANT4 code, we show that the deflection angle exponentially decays as a function of energy, and the numerical values for the current configuration are below the detector accuracy except the initial energy bins owing to the low-Z, low density, and low thickness of the current plastic scintillators. This implies the necessity of additional components that provoke the muon scattering. Therefore, we introduce stainless steel surfaces into the top and bottom sections in order to amplify the deflection angle as well as to reduce the uncertainty, thereby improving the detector performance.

physics.ins-det↗

arXiv2022

Particle generation through restrictive planes in GEANT4 simulations for potential applications of cosmic ray muon tomography

In this study, by attempting to resolve the angular complication during the particle generation for the muon tomography applications in the GEANT4 simulations, we exhibit an unconventional methodology that is hinged on the direction limitation via the vectorial construction from the generation location to the restriction area rather than using a certain angular distribution or interval. In other words, we favor a momentum direction that is determined by a vector constructed between an initial point randomly chosen on a generative point/plane and a latter point arbitrarily selected on a restrictive plane of the same dimensions with the basal cross section of the volume-of-interest (VOI). On account of setting out such a generation scheme, we optimize the particle loss by keeping an angular disparity that is directly dependent on the VOI geometry as well as the vertical position of the restrictive plane for a tomographic system of a finite size. We demonstrate our strategy for a set of target materials including aluminum, copper, iron, lead, and uranium with a dimension of 40$\times$10$\times$40 $\rm cm^{3}$ over three restrictive planes of different positions by using a discrete energy spectrum between 0.1 and 8 GeV and we compute the scattering angle, the number of absorption, and the particle loss. Upon our simulation outcomes, we show that the particle generation by means of restrictive planes is an effective strategy that is flexible towards a variety of computational objectives in the GEANT4 simulations.

physics.comp-ph↗

arXiv2021

On muon energy group structure based on deflection angle for application in muon scattering tomography: A Monte Carlo study through GEANT4 simulations

The average deflection angle of the tracked muons in the muon scattering tomography exponentially declines in function of the initial kinetic energy, the angular dependence of which provides an opportunity to set out a binary relation between the initial kinetic energy and the average deflection angle, thereby leading to a coarse energy prediction founded on the mean deflection angle in the case of experimental incapabilities or limitations. In this study, we address the problem of the muon energy classification for a tomographic system consisting of 0.4-cm plastic scintillators manufactured from polyvinyl toluene and we explore a four-group structure besides a ternary partitioning between 0.25 and 8 GeV. In the first instance, we determine the deflection angles by tracking the hit locations in the detector layers on the sub-divided uniform energy intervals through the GEANT4 simulations. In the latter step, we express two misclassification probabilities where the first approach assumes a symmetrical linear propagation bounded by one standard deviation in one dimension, whereas the second procedure employs a positively defined modified Gaussian distribution that governs the overlapping area in two dimensions. In the final stage, we compare qualitatively and quantitatively the adjacent energy groups by using the computed misclassification probabilities. In the absence of any further data manipulation, we explicitly show that the misclassification probabilities increase when the number of energy groups augments. Furthermore, we also conclude that it is feasible to benefit from the mean deflection angle to roughly estimate the muon energies up to four energy groups by taking the misclassification probabilities into consideration, while the classification viability significantly diminishes when the partition number exceeds four on the basis of standard deviation.

physics.ins-det↗

arXiv2021

Effect of passive metallic layers on muon energy estimation by means of deflection angle for muon scattering tomography: A comparative study based on GEANT4 simulations

In the tomographic configurations based on the muon scattering, the angular variation with respect to the kinetic energy indirectly brings forth the ability to coarsely predict the kinetic energy by using the deflection angle owing to the detector layers. Nevertheless, the angular deviation due to the detector components is expected to be minuscule in addition to a relatively high uncertainty in the case of the plastic scintillators. In the present study, we contrast our current tomographic prototype, which consists of the detector layers manufactured from polyvinyl toluene besides a detector accuracy of 1 mrad, with an alternative hodoscope scheme containing stainless steel layers by aiming to investigate the three-group energy structure. Initially, we determine the average deflection angles together with the corresponding standard deviations for our present setup as well as for the alternative scheme by means of the GEANT4 simulations. In the second place, we express a brace of misclassification probabilities founded on the standard deviations where the first procedure assumes a linear finite approximation, whereas the latter approach rests on a positively defined modified Gaussian distribution. Upon our simulation results, we demonstrate that the introduced stainless steel layers in the proposed hodoscope setup do not only serve to augment the average deflection angles, but they also diminish the misclassification probabilities, therewith reducing the classification uncertainty apart from an improved detection performance.

physics.ins-det↗

arXiv2021

Unveiling triangular correlation of angular deviation in muon scattering tomography by means of GEANT4 simulations

The angular deviation commonly represented by the scattering angle generally serves to provide the characteristic discrimination in the muon scattering tomography. The regular procedure to determine the scattering angle comprises the collection of exactly four hit locations in four detector layers among which two top detector layers are utilized to construct the first vector, whereas the second vector is built by using two bottom detector layers. Although this procedure acts to classify the target volumes in the tomographic systems based on the muon scattering, the scattering angle obtained through the usual methodology founded on four detector layers is dubious for not yielding any information about the position of target volume. Nonetheless, the same set of four detector layers also imparts the possibility of splitting the scattering angle into two separate angles by creating a triangular correlation in such a way that the scattering angle is referred to an exterior angle, whereas the separate angles are considered the interior opposite angles that are not neighboring this exterior angle. In this study, we first show that a combination of three detector layers out of four fulfills the calculation of the interior opposite angles. Then, by employing the GEANT4 simulations over our tomographic configuration composed of three plastic scintillators in either section, we demonstrate that the interior opposite angles differ towards the vertical spatial variation, while the exterior angle approximately remains constant, thereby implying a beneficial feature to be used for the image reconstruction purposes.

physics.ins-det↗

arXiv2018

3D Surface Radiation Dosimetry of a Nuclear-Chicago NH3 Neutron Howitzer

The tracking of radiation dose is a fundamental concept for the safe operation of nuclear instruments, and this concept is a multi-task challenge in the case of neutron sources since not only the neutron emissions from the main radioactive source but also the neutron capture gamma-rays as well as the gamma-rays from the inelastic neutron scattering make contribution to the total dose received by the facility personnel. The present study is devoted to the assessment of the equivalent dose rates on the surface of a Nuclear-Chicago NH3 neutron howitzer with a 5-Ci 239Pu-Be neutron source by means of Monte Carlo simulations. The 5-Ci 239Pu-Be neutron source is mounted within a vertical aluminum channel at the center of the neutron howitzer, and we use the axial symmetry of the aluminum drum filled with an ordinary paraffin without any potent neutron absorber such as boron or cadmium. We utilise the ICRP-21 flux-to-dose rate conversion factors and we track the neutron and photon equivalent dose rates on the lateral and top surfaces including the outlets of the vertical and horizontal irradiation channels by the aid of point detectors in the MCNP5 code. From the results over a number of sub-regions on the semi-cylindrical drum of the Nuclear-Chicago NH3 neutron howitzer, we show that the outlets of both the vertical and horizontal irradiation channels deliver approximately the same level of equivalent dose rates, and the maximum equivalent dose rates for neutrons and photons on the lateral surface are obtained at the spatial coordinates aligned with the location of the 5-Ci 239Pu-Be neutron source, whereas the periphery around the source channel on the top surface of the neutron howitzer constitutes the highest level of equivalent dose rates among the tracked locations.

physics.med-ph↗

arXiv2018

Neutronic Analysis of a Nuclear-Chicago NH3 Neutron Howitzer

Neutron howitzers are the irradiation instruments, generally used for the chemical analysis in the research laboratories, where the neutron sources are encapsulated within a moderating medium and the target materials are irradiated at the channels inserted through the corresponding neutron sources. In this study, we employ Monte Carlo simulations by using the MCNP5 code in order to perform the neutronic analysis of a Nuclear-Chicago NH3 neutron howitzer with a 5-Ci 239Pu-Be neutron source. This neutron howitzer is a cylindrical drum that is covered by aluminum at the level of outermost layer, and the cylindrical body is installed with paraffin for the neutron moderation. The drum consists of two vertical and two horizontal irradiation channels and a vertical source channel in which the 5-Ci 239Pu-Be neutron source is located and moved upward or downward by the aid of a plexiglass rod. We focus our study on the two horizontal irradiation channels, separated by an angle of 120o, which are installed with a cylindrical plexiglass bar. We construct our geometry by respecting the dimensional properties of the NH3 howitzer components and we define a biased cylindrical source of 1.02 in.x 4.425 in. by taking into account the neutron energy spectrum and source strength of the 5-Ci 239Pu-Be neutron source. We determine the neutron flux within the plexiglass bar for various energy bins in the energy range between 0 and 10.5 MeV, and also, we investigate the axial variation of the neutron flux along the plexiglass region in the horizontal irradiation channels. Our simulation results show that a significant number of thermal neutrons as well as a non-negligible population of fast neutrons propagate through the plexiglass bar, thereby demonstrating the opportunity to product from a wide range of energy spectrum for the neutron activation analysis.

physics.ins-det↗

arXiv2015

Enabling microstructural changes of FCC/BCC alloys in 2D dislocation dynamics

Dimension reduction procedure is the recipe to represent defects in two dimensional dislocation dynamics according to the changes in the geometrical properties of the defects triggered by different conditions such as radiation, high temperature, or pressure. In the present study, this procedure is extended to incorporate further features related to the presence of defects with a special focus on face-centered cubic/body-centered cubic alloys used for diverse engineering purposes. In order to reflect the microstructural state of the alloy on the computational cell of two dimensional dislocation dynamics, the distribution of the multi-type defects over slip lines is implemented by using corresponding strength and line spacing for each type of defect. Additionally, a simple recursive incremental relation is set to count the loop accumulation on the precipitates. In the case of continuous resistance against the motion of edge dislocations on the slip lines, an expression of friction is introduced to see its contribution on the yield strength. Each new property is applied independently on a different material by using experimental information about defect properties and grain sizes under the condition of plain strain deformation: both constant and dynamically increasing obstacle strength for precipitate coarsening in prime-aged and heat-treated copper-chromium-zirconium, internal friction in tantalum-2.5tungsten, and mixed hardening due to the presence of precipitates and prismatic loops in irradiated oxide dispersion strengthened EUROFER with 0.3% yttria.

cond-mat.mtrl-sci↗