• Nuclear Engineering and Technology
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• 제54권2호
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• pp.701-708
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• 2022

The mass attenuation coefficients (μ_m) of polyethylene glycol (PEG) of different molecular weights (1000-200,000) were measured using single-beam photon transmission. The X-ray fluorescent (XRF) photons from Zinc (Zn), Zirconium (Zr), Molybdenum (Mo), Silver (Ag) and Cadmium (Cd) targets were used to determine the attenuation of gamma radiation of energy range between 8.67 and 23.19 keV in PEG samples. The results were compared to theoretical values using XCOM and Monte Carlo simulation using Geant4 toolkit which was developed to validate the experiment at those certain energies. The mass attenuation coefficients were then used to compute the effective atomic numbers, electron density and half value layers for the studied samples. The outcomes showed good agreement between experimental and simulated results with those calculated theoretically by XCOM within 5% deviation. The PEG 1000 sample showed slightly higher μ_m value compared with the other samples. The dependence of the photon energy and PEG composition on the values of μ_m and HVL were investigated and discussed. In addition, the values of Z_eff and N_eff for all PEG samples behaved similarly in the given photon energy range, and they decreased as the photon energy increased.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.283-292
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• 2022

Advanced radiation applications have been widely used and extended to many fields. As a result of this fact, choosing an appropriate shielding material based on the radiation application has become vital. In this regard, the integration of elements into polymer composites has been investigated and contributed to the quantity and quality of radiation shielding materials. This study reports photon attenuation parameters and electromagnetic shielding effectiveness of a novel polymer composite prepared with a matrix reinforced with three different proportions (5, 10, and 15 wt%) of niobium content. Addition of Nb dopant improves both photon attenuation and electromagnetic shielding effectiveness for the investigated composites. Therefore, Nb(15%) polymer composite with highest concentration has been found to be the best absorber for ionizing and non-ionizing radiations. Consequently, the performed analyzes provide evidences that the prepared Nb-reinforced polymer composite could be effectively used as photon radiation attenuator and electromagnetic shielding material.

• 한국방사선학회논문지
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• 제17권4호
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• pp.507-514
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• 2023

이 연구의 목적은 유방촬영의 X-선 빔에서 유효광자에너지를 쉽게 계산할 수 있는 계산식을 구하는데 있다. X2 MAM Sensor를 사용하여 각각의 설정관전압에 대하여 측정관전압을 얻었다. 알루미늄 여과체의 알루미늄에 대한 질량감쇠계수는 각각의 측정관전압 X-선 빔에서 반가층 측정으로부터 구하였다. 각각의 측정관전압 X-선 빔으로부터 구하여진 알루미늄의 질량감쇠계수는 NIST로부터 얻어진 광자에너지별 알루미늄의 질량감쇠계수에 대응시켰다. 일치하는 질량감쇠계수에 대응하는 광자에너지가 유효광자에너지로 결정되었다. 결정된 유효광자에너지의 계산식은 Origin pro 2019b 통계프로그램에서 각각의 측정관전압에 대한 유효광자에너지를 다항식으로 정합하여 y=28.98968-1.91738x+0.07786x²-0.000946717x³으로 얻었다. 여기서 x는 측정관전압이고, y는 유효광자에너지이다. 이 연구에서 얻어진 유방촬영 X-선 빔의 유효광자에너지의 계산식은 임상에서 X-선 빔과 어떤 물질과의 상호작용 계수를 구하는데 아주 유용하게 사용될 수 있을 것으로 사료된다.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.241-246
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• 2024

The study was carried out by numerical integration based on the diffraction properties and elemental composition. The elemental compositions of breast tissues in the literature were tested. The photon attenuation coefficients calculated using the recent elemental composition were found within 0.2-16% for adipose tissue and within 0.04-17% for glandular tissue with the experimental reference data. The attenuation coefficients of cancerous breast tissue calculated according to the elemental content previously measured in breast cancer patients were found within 0-17% with experimental data in the literature. The attenuation coefficients are of great interest to medical research. To calculate realistic attenuation coefficients, the characteristic coherent scatter, which is most intense at small angles, must be considered. For this reason, experimentally measured form factor data were reviewed, and the most compatible one with the theoretical form factor data produced in this study was used at low momentum transfer x (0 < x ≤ 8 nm^-1). The differential linear coherent scattering distributions were calculated for an energy value of 17.44 keV and compared with their experimental counterparts.

• 한국진공학회지
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• 제8권2호
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• pp.102-110
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• 1999

The LIGA X-ray exposure step was modelled into three inequalities, by assuming that the X-ray energy attenuated within a resist is deposited only in the localized range of the resist. From these inequalities, equations for the minimum and maximum exposure times required for a good quality microstructure were obtained. Also, an equation for the thickness of an X-ray mask absorber was obtained from the exposure requirement of threshold dose deposition. The calculation method of the synchrotron radiation power from a synchrotron radiation source was introduced and applied to an X-ray exposure step. A power from a synchrotron radiation source was introduced and applied to an X-ray exposure step/ A power function of photon energy, approximating the attenuation length of the representative LIGA resist, PMMA, and the mean photon energy of the XZ-rays incident upon an X-ray mask absorber were applied to the above mentioned equations. Consequently, the tendencies of the minimum and maximum exposure and with respect to mean photon energy and thick ness of PMMA was obtained. Additionally, the tendencies of the necessary thickness of PMMA and photon energy of the X-ray mask absorber with respect to thickness of PMMA and photon energy of the X-rays incident upon an X-ray mask absorber were examined. The minimum exposure time increases monotonically with increasing mean photon energy for the same total power density and is not a function of the thickness of resist. The minimum exposure time increases with increasing mean photon energy for the same total power density in the case of the general LIGA process, where the thickness of PMMA is thinner than the attenuation length of PMMA. Additionally, the minimum exposure time increases monotonically with increasing thickness of PMMA. The maximally exposable thickness of resist is proportional to the attenuation length of the resist at the mean photon energy with its proportional constant of ln $(Dd_m/D_{dv})$. The necessary thickness of a gold X-ray mask absorber due to absorption edges of gold, increases smoothly with increasing PMMA thickness ratio, and is independent of the total power density itself. The simplicity of the derived equations has made clearly understandable the X-ray exposure phenomenon and the correlation among the exposure times, the attenuation coefficient and the thickness of an X-ray mask absorber, the attenuation coefficient and the thickness of the resist, and the synchrotron radiation power density.

• 한국방사선학회논문지
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• 제16권1호
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• pp.61-66
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• 2022

이 연구의 목적은 Ir¹⁹² 선원을 이용한 근접치료에서 물 흡수선량 1 Gy에 대한 광자 에너지플루언스와 질량에너지흡수계수를 유도하는데 있다. Khan이 저술한 방사선치료물리학으로부터 Ir¹⁹² 선원의 감마선 선속에 대한 납의 반가층을 얻었다. 얻어진 납의 반가층으로부터 선감쇠계수와 질량감쇠계수를 산출하였다. 산출된 납의 질량감쇠계수를 NIST의 납의 질량감쇠계수 자료에 대응시켜 일치하는 질량감쇠계수의 광자에너지를 유효에너지로 결정하였다. 결정된 유효에너지를 NIST의 물의 질량에너지흡수계수 자료의 광자에너지에 대응시켜서, 물의 질량에너지흡수계수는 0.03273 cm²/g(32.73 cm²/kg)으로 얻었다. 얻어진 물의 질량에너지흡수계수(32.73 cm²/kg)를 물 흡수선량 1 Gy에 나누어 광자에너지플루언스는 0.03055 J/cm²으로 산출하였다.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1364-1371
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• 2018

An extensive investigation of photon interaction properties has been made for $Zn_xTe_{100-x}$ alloys (where x = 5, 20, 30, 40, 50) to explore its possible use in sensing and shielding gamma radiations. The results show better and stable response of ZnTe alloys for various photon interaction properties over the wide energy range, with an additional benefit of ease in fabrication due to lower melting points of Zn and Te. Mass attenuation coefficient values show strong dependence on photon energy as well as composition. Effective atomic number has maximum value for $Zn_5Te_{95}$ and lowest for $Zn_{50}Te_{50}$ in the entire energy region. The alloy sample with maximum $Z_{eff}$ shows minimal value of $N_e$ and vice versa. Mean free path follows inverse trend as observed for mass attenuation coefficient. The exposure and energy absorption buildup factors depend upon photon energy, penetration thickness and composition (effective atomic number) of $Zn_xTe_{100-x}$ alloys. It finds its application for sensing and shielding from highly energetic and highly penetrating photons at sites where radioactive materials were used and visibility of material is not a big constraint. Further, energy down conversion property of ZnTe alloys with subsequent emission in green band suggests its potential use in sensing gamma photons.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2003년도 제27회 추계학술대회
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• pp.41-41
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• 2003

Purpose: Even if the wedge filter is widely used for the radiation therapy to modify the photon beam intensity, the wedged photon beam dose calculation is not so easy. Radiation therapy planning systems (RTPS) have been used the empirical or semi-analytical methods such as attenuation method using wedge filter parameters or wedge filter factor obtained from measurement. However, these methods can cause serious error in penumbra region as well as in edge region. In this study, we propose the dose calculation algorithm for wedged field to minimize the error especially in the outer beam region. Materials and Method: Modified intensity by wedge filter was calculated using tissue-maximum ratio (TMR) and scatter-maximum ratio (SMR) of wedged field. Profiles of wedged and non-wedged direction was also used. The result of new dose calculation was compared with measurement and the result from attenuation method. Results: Proposed algorithm showed the good agreement with measurement in the high dose-gradient region as well as in the inner beam region. The error was decreased comparing to attenuation method. Conclusion: Although necessary beam data for the RTPS commissioning was increased, new algorithm would guarantee the improved dose calculation accuracy for wedged field. In future, this algorithm could be adopted in RTPS.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3470-3477
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• 2022

Soils are porous materials with high shielding capability to attenuate gamma and X-rays. The disposal of radionuclides throughout the soil profile can expose the living organisms to ionizing radiation. Thus, studies aiming to analyze the shielding properties of the soils are of particular interest for radiation shielding. Investigations on evaluating the shielding capabilities of highly weathered soils are still scarce, meaning that additional research is necessary to check their efficiency to attenuate radiation. In this study, the radiation shielding properties of contrasting soils were evaluated. The radiation interaction parameters assessed were attenuation coefficients, mean free path, and half- and tenth-value layers. At low photon energies, the photoelectric absorption contribution to the attenuation coefficient predominated, while at intermediate and high photon energies, the incoherent scattering and pair production were the dominant effects. Soils with the highest densities presented the best shielding properties, regardless of their chemical compositions. Increases in the attenuation coefficient and decreases in shielding parameters of the soils were associated with increases in clay, Fe₂O₃, Al₂O₃, and TiO₂ amounts. In addition, this paper provides a comprehensive description of the shielding properties of weathered soils showing the importance of their granulometric fractions and oxides to the attenuation of the radiation.

• Nuclear Engineering and Technology
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• 제51권8호
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• pp.2005-2012
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• 2019

This work investigated the radiation attenuation characteristics of three series of tellurite glass systems with the following compositions: 30PbO-10ZnO-xTeO₂-(60-x)B₂O₃ where x = 10, 30, 40, 50 and 60 mol%, xBaO-xB₂O₃-(100-2x)TeO₂ with x = 15-40 mol% and 50ZnO-(50-x)P₂O₅-xTeO₂, where x = 0, 10, .40 mol%. The results revealed that the attenuation parameters in all the samples decrease with increase in the energy, which implied that all the samples have better interaction with gamma photons at low energies and thus higher photon attenuating efficiency. From the three systems, the samples coded as PbZnBTe60, BaBTe70 and ZnPTe40 have the lowest half value layer values and accordingly have superior photon attenuation efficacy. The maximum effective atomic number values were found for energy less than 0.1 MeV particularly near the K-edges absorption of the heavy atomic number elements such as Te, Ba and Pb. At the lowest energy, the Z_eff values are found in the range of 62.33-66.25, 49.43-50.81 and 24.99-35.83 for series 1-3 respectively. Also, we found that the density of the glass remarkably affects the photon attenuation ability of the selected glasses. The mean free path results showed that the PbO-ZnO-TeO₂-B₂O₃ glass system has better radiation shielding efficiency than the glass samples in series 2 and 3.