• Journal of the Korean Society of Safety
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• v.32 no.6
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• pp.29-33
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• 2017

In order to solve this sort of electrostatic failure in Display and Semiconductor process, Soft X-ray ionizer is mainly used. Soft X-ray Ionizer does not only generate electrical noise and minute particle but also is efficient to remove electrostatic as it has a wide range of ionization. There exist variable factors such as type of tungsten thickness deposited on target, Anode voltage etc., and it takes a lot of time and financial resource to find optimal performance by manufacturing with actual X-ray tube source. Here, MCNPX (Monte Carlo N-Particle Extended) is used for simulation to solve this kind of problem, and optimum efficiency of X-ray generation is anticipated. In this study, X-ray generation efficiency was compared according to target material thickness using MCNPX and actual X-ray tube source under the conditions that tube voltage is 5 keV, 10 keV, 15 keV and the target Material is Tungsten(W). At the result, In Tube voltage 5 keV and distance 100 mm, optimal target thickness is $0.05{\mu}m$ and fastest decay time appears + decay time 0.28 sec. - deacy time 0.30 sec. In Tube voltage 10keV and distance 100 mm, optimal target Thickness is $0.16{\mu}m$ and fastest decay time appears + decay time 0.13 sec. - deacy time 0.12 sec. In the tube voltage 15 keV and distance 100 mm, optimal target Thickness is $0.28{\mu}m$ and fastest decay time appears + decay time 0.04 sec. - deacy time 0.05 sec.

• Progress in Medical Physics
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• v.31 no.2
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• pp.29-34
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• 2020

Purpose: The interaction of various substances inserted into the human body and radiation can confirm the radiation enhancement effect. A Leksell frame inserted into the human body for gamma knife treatment will cause not only pain and inconvenience to the patient, but also additional exposure to the patient's normal tissues. In this study, we attempt to confirm the additional exposure caused by the interaction of the Leksell frame and thermoplastic mask, and ⁶⁰Co used for gamma knife treatment. Methods: A ⁶⁰Co energy of 1.17, 1.33 MeV is applied using Monte Carlo simulation, and fixation screws and thermoplastic mask are fabricated using aluminum and titanium alloy, and Carbon compounds. Results: Results show a dose enhancement of up to 396.27% higher compared with that without a Leksell frame and up to 391.25% in thermoplastic mask. Conclusions: Hence, appropriate treatment methods and materials must be used to reduce additional exposure to normal tissues.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3401-3408
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• 2023

In this study, we used the Monte Carlo N-Particle program to simulate the gamma-ray spectra obtained from plastic scintillators holes filled with bismuth nanoparticles. We confirmed that the incorporation of bismuth nanoparticles into a plastic scintillator enhances its performance for gamma-ray spectroscopy using the subtraction method. The subtracted energy spectra obtained from the bismuth-nanoparticle-incorporated and the original plastic scintillator exhibit a distinct energy peak that does not appear in the corresponding original spectra. We varied the diameter and depth of the bismuth-filled holes to determine the optimal hole design for gamma-ray spectroscopy using the subtraction method. We evaluated the energy resolutions of the energy peaks in the gamma-ray spectra to estimate the effects of the bismuth nanoparticles and determine their optimum volume in the plastic scintillator. In addition, we calculated the peak-to-total ratio of the energy spectrum to evaluate the energy measuring limit of the bismuth nanoparticle-containing plastic scintillator using the subtraction method.

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.801-809
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• 2017

The purpose of this study is to assess the additional neutron effective dose during passive scattering proton therapy. Monte Carlo code (Monte Carlo N-Particle 6) simulation was conducted based on a precise modeling of the National Cancer Center's proton therapy facility. A three-dimensional neutron effective dose profile of the interior of the treatment room was acquired via a computer simulation of the 217.8-MeV proton beam. Measurements were taken with a $^3He$ neutron detector to support the simulation results, which were lower than the simulation results by 16% on average. The secondary photon dose was about 0.8% of the neutron dose. The dominant neutron source was deduced based on flux calculation. The secondary neutron effective dose per proton absorbed dose ranged from $4.942{\pm}0.031mSv/Gy$ at the end of the field to $0.324{\pm}0.006mSv/Gy$ at 150 cm in axial distance.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.546-558
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• 2015

Chord length sampling method in Monte Carlo simulations is a method used to model spherical particles with random sampling technique in a stochastic media. It has received attention due to the high calculation efficiency as well as user convenience; however, a technical issue regarding boundary effect has been noted. In this study, after analyzing the distribution characteristics of spherical particles using an explicit method, an alternative chord length sampling method is proposed. In addition, for modeling in finite media, a correction method of the boundary effect is proposed. Using the proposed method, sample probability distributions and relative errors were estimated and compared with those calculated by the explicit method. The results show that the reconstruction ability and modeling accuracy of the particle probability distribution with the proposed method were considerably high. Also, from the local packing fraction results, the proposed method can successfully solve the boundary effect problem. It is expected that the proposed method can contribute to the increasing of the modeling accuracy in stochastic media.

• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.34-37
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• 2017

In recent emerging industry, Display field becomes bigger and bigger, and also semiconductor technology becomes high density integration. In Flat Panel Display, there is an issue that electrostatic phenomenon results in fine dust adsorption as electrostatic capacity increases due to bigger size. Destruction of high integrated circuit and pattern deterioration occur in semiconductor and this causes the problem of weakening of thermal resistance. In order to solve this sort of electrostatic failure in this process, Soft X-ray ionizer is mainly used. Soft X-ray Ionizer does not only generate electrical noise and minute particle but also is efficient to remove electrostatic as it has a wide range of ionization. X-ray Generating efficiency has an effect on soft X-ray Ionizer affects neutralizing performance. There exist variable factors such as type of anode, thickness, tube voltage etc., and it takes a lot of time and financial resource to find optimal performance by manufacturing with actual X-ray tube source. MCNPX (Monte Carlo N-Particle Extended) is used for simulation to solve this kind of problem, and optimum efficiency of X-ray generation is anticipated. In this study, X-ray generation efficiency was measured according to target material thickness using MCNPX under the conditions that tube voltage is 5 keV, 10 keV, 15 keV and the target Material is Tungsten(W), Gold(Au), Silver(Ag). At the result, Gold(Au) shows optimum efficiency. In Tube voltage 5 keV, optimal target thickness is $0.05{\mu}m$ and Largest energy of Light flux appears $2.22{\times}10^8$ x-ray flux. In Tube voltage 10 keV, optimal target Thickness is $0.18{\mu}m$ and Largest energy of Light flux appears $1.97{\times}10^9$ x-ray flux. In Tube voltage 15 keV, optimal target Thickness is $0.29{\mu}m$ and Largest energy of Light flux appears $4.59{\times}10^9$ x-ray flux.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.227-234
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• 2012

In this study, we make simulation of density log using a Monte Carlo N-Particle (MCNP) algorithm to make an analysis on density logging under different borehole environments, since density logging is affected by various borehole conditions like borehole size, density of borehole fluid, thickness and type of casing, and so on. MCNP algorithm has been widely used for simulation of problems of nuclear particle transportation. In the simulation, we consider the specific configuration of a tool (Robertson Geologging Co. Ltd) that Korea institute of geoscience and mineral resources (KIGAM) has used. In order to measure accurate bulk density of a formation, it is essential to make a calibration and correction chart for the tool under considerations. Through numerical simulation, this study makes calibration plot of the density tool in material with several known bulk densities and with boreholes of several different diameters. In order to make correction charts for the density logging, we simulate and analyze measurements of density logging under different borehole conditions by considering borehole size, density of borehole fluid, and presence of casing.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4244-4252
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• 2022

The accuracy of Monte Carlo (MC) simulations in estimating the computed tomography radiation dose is highly dependent on the accuracy of CT scanner model. A system was developed to observe the 3D model intuitively and to calculate the X-ray energy spectrum and the bowtie (BT) filter model more accurately in Monte Carlo N-particle (MCNP). Labview's built-in Open Graphics Library (OpenGL) was used to display basic surfaces, and constructive solid geometry (CSG) method was used to realize Boolean operations. The energy spectrum was calculated by simulating the process of electronic shooting and the BT filter model was accurately modeled based on the calculated shape curve. Physical data from a study was used as an example to illustrate the accuracy of the constructed model. RMSE between the simulation and the measurement results were 0.97% and 0.74% for two filters of different shapes. It can be seen from the comparison results that to obtain an accurate CT scanner model, physical measurements should be taken as the standard. The energy spectrum library should be established based on Monte Carlo simulations with modifiable input files. It is necessary to use the three-segment splicing modeling method to construct the bowtie filter model.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.219-226
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• 2012

This study provides an analysis on results of neutron logging for various borehole environments through numerical simulation based on a Monte Carlo N-Particle (MCNP) code developed and maintained by Los Alamos National Laboratory. MCNP is suitable for the simulation of neutron logging since the algorithm can simulate transport of nuclear particles in three-dimensional geometry. Rather than simulating a specific tool of a particular service company between many commercial neutron tools, we have constructed a generic thermal neutron tool characterizing commercial tools. This study makes calibration chart of the neutron logging tool for materials (e.g., limestone, sandstone and dolomite) with various porosities. Further, we provides correction charts for the generic neutron logging tool to analyze responses of the tool under various borehole conditions by considering brine-filled borehole fluid and void water, and presence of borehole fluid.

• Journal of radiological science and technology
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• v.45 no.4
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• pp.331-339
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• 2022

The purpose of this study was to evaluate maternal organ and fetal doses by week of pregnancy for pregnant women nuclear medicine practitioners in the nuclear medicine field. In addition, we intend to present basic data for the management of exposure doses of female nuclear medicine practitioners. In this study, phantoms of childbearing women, 3, 6, 9 months pregnant women were simulated using MCNPX(Monte Carlo N-Particle Extended) among the Monte Carlo methods. First, volume source was constructed based on 10 cm of the anterior part of the lower abdomen of the phantom, and the organ and fetal doses were evaluated for each week of the pregnant woman according to the type of radioactive isotope. Second, the organ and fetal dose of pregnant women were evaluated by increasing the distance between the source and the abdominal surface by 50 and 100 cm. As a result, ¹⁸F sources showed high organ and fetal doses in pregnant women 0 to 3 months, and the dose distribution gradually decreased in 6 to 9 months pregnant women. The distribution of organ and fetal doses for ⁹⁹mTc and ¹²³I sources showed the same tendency as that of ¹⁸F, and the overall absorbed dose distribution was relatively lower than that of ¹⁸F. Through this study, it is considered that workers in the early stages of pregnancy within 3 months will need appropriate management to minimize occupational exposure dose.