• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(2)
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• pp.45-48
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• 2002

This paper discusses the surface roughness of negative chemically amplified resists, SAL601 exposed by I-beam direct writing. system. Surface roughness, as measured by atomic force microscopy, have been simulated and compared to experimental results. Molecular-scale simulator predicts the roughness dependence on material properties and process conditions. A chemical amplification is made to occur in the resists during PEB process. Monte-Carlo and exposure simulations are used as the same program as before. However, molecular-scale PEB simulation has been remodeled using a two-dimensional molecular lattice representation of the polymer matrix. Changes in surface roughness are shown to correlate with the dose of exposure and tile baking time of PEB process. The result of simulation has a similar tendency with that of experiment.

• 천문학회보
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• 제42권2호
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• pp.86.4-87
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• 2017

Symbiotic stars are binary systems composed of a hot white dwarf and a mass losing giant. Many symbiotic stars are known to exhibit broad wings around Balmer emission line. We show high resolution spectra of S-type symbiotic stars, Z Andromedae and AG Draconis, obtained with the ESPaDOnS and the 3.6 m Canada-France-Hawaii Telescope, in which we find prominent broad wings around Balmer lines. We adopt Monte-Carlo technique to consider two types of wing formation mechanisms, which are Thomson scattering by free electron in H II region and Raman scattering by atomic hydrogen in H I region. We find that Thomson wings of $H{\alpha}$ and $H{\beta}$ have the same widths in the Doppler space due to the cross section independent of wavelength. In contrast, Raman $H{\alpha}$ wings are 3 times broader widths than $H{\beta}$ counterparts, which is attributed to the different cross sections and branching ratios. Our CFHT data show that $H{\alpha}$ wings of Z Andromedae and AG Draconis are broader than $H{\beta}$ wings, lending strong support to the Raman scattering origin of Balmer wings in these objects.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 영호남 합동 학술대회 및 춘계학술대회 논문집 센서 박막 기술교육
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• pp.15-19
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• 2006

A pulsed laser ablation deposition (PLAD) technique is an excellent method for the fabrication of amorphous carbon (a-C) films, because it can generate highly energetic carbon clusters on a substrate. This paper was focused on the understanding and analysis of the motion of C particles in laser ablation assisted by Ar plasmas. The simulation has carried out under the pressure P=50 mTorr of Ar plasmas. Two-dimensional hybrid model consisting of fluid and Monte-Carlo models was developed and three kinds of the ablated particles which are carbon atom (C), ion ($C^+$) and electron were considered in the calculation of particle method. The motions of energetic $C^+$ and C deposited upon the substrate were investigated and compared. The interactions between the ablated particles and Ar gas plasmas were discussed.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(4)
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• pp.101-106
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• 1996

For the application of the neutron flux mapping, an accurate calculation of the sensitivity is required because the sensitivity is proportional to the neutron flux density. Sensitivity is defined as the current per unit length per unit neutron flux and it mainly depends on the depression factor(f), the escape probability from the emitter($\varepsilon$1) and the charge build-up factor of the insulator layer(c). A Monte Carlo simulation was accomplished to calculate the sensitivity of rhodium emitter material and alumina(Al$_2$O$_3$) insulator with a cylindrical geometry, based on the (n,${\beta}$) interaction and on other interaction including the secondary electron generation for the more accurate estimation of the sensitivity. From the simulation results, factors fur the sensitivity were accurately calculated and compared with other theoretical and experimental values. In addition, the sensitivity linearly increases and saturates as the emitter radius increases. The accomplished method is useful in the analysis for the change of SPND sensitivity as a function of burn-up and in the optimum design of SPND.

• Nuclear Engineering and Technology
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• 제36권2호
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• pp.121-126
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• 2004

3-PM liquid scintillation counting using the geometry-efficiency variation technique has been applied to the activity measurement of $^{204}T1$, which decays to $^{204}Hg\;and\;^{204}Pb\;by\;{\beta}^-$ and E.C., respectively. The TDCR values K have been derived over a wide range, 0.78 < K < 0.97, by displacing the detectors up to 50 mm away from an unquenched liquid scintillation sample $^{204}Tl$. The derived plots of the logic sums of double coincidences $N_D(K)$ very K vary linearly in the observed regions. The fractions of losses due to electron capture decay have been taken into account by employing a PENELOPE Monte Carlo simulation. The calibrated activity is 102.3 kBq at a reference date of July 1st, 2002 (UT) with a combined uncertainty of $0.63\%$. This is consistent with the value determined by means of the CIEMAT/NIST method at KRISS.

• 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.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.312-312
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• 2011

In SiH4/H2 discharge for growth process of hydrogenated amorphous silicon (a-Si:H), silane polymers, produced by SiH2 + Sin-1H2n ${\rightarrow}$ SinH2n+2, have no reactivity on the film-growing surface. However, under the SiH2 rich condition, high silane reactive species (HSRS) can be produced by electron collision to silane polymers. HSRS, having relatively strong reactivity on the surface, can react with dangling bond and form Si-H2 networks which have a close correlation with photo-induced degradation of a-Si:H thin film solar cell [1]. To find contributions of suggested several external plasma conditions (pressure, frequency and ratio of mixture gas) [2,3] to suppressing productions of HSRS, some plasma characteristics are studied by numerical methods. For this study, a zero-dimensional global model for SiH4/H2 discharge and a one-dimensional particle-in-cell Monte-Carlo-collision model (PIC-MCC) for pure SiH4 discharge have been developed. Densities of important reactive species of SiH4/H2 discharge are observed by means of the global model, dealing 30 species and 136 reactions, and electron energy probability functions (EEPFs) of pure SiH4 discharge are obtained from the PIC-MCC model, containing 5 charged species and 15 reactions. Using global model, SiH2/SiH3 values were calculated when pressure and driving frequency vary from 0.1 Torr to 10 Torr, from 13.56 MHz to 60 MHz respectively and when the portion of hydrogen changes. Due to the limitation of global model, frequency effects can be explained by PIC-MCC model. Through PIC-MCC model for pure SiH4, EEPFs are obtained in the specific range responsible for forming SiH2 and SiH3: from 8.75 eV to 9.47 eV [4]. Through densities of reactive species and EEPFs, polymerization reactions and production of HSRS are discussed.

• Nuclear Engineering and Technology
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• 제48권1호
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• pp.55-63
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• 2016

Calculation of the core neutronic parameters is one of the key components in all nuclear reactors. In this research, the energy spectrum and spatial distribution of the neutron flux in a uranium target have been calculated. In addition, sensitivity of the core neutronic parameters in accelerator-driven subcritical advanced liquid metal reactors, such as electron beam energy ($E_e$) and source multiplication coefficient ($k_s$), has been investigated. A Monte Carlo code (MCNPX_2.6) has been used to calculate neutronic parameters such as effective multiplication coefficient ($k_{eff}$), net neutron multiplication (M), neutron yield ($Y_{n/e}$), energy constant gain ($G_0$), energy gain (G), importance of neutron source (${\varphi}^*$), axial and radial distributions of neutron flux, and power peaking factor ($P_{max}/P_{ave}$) in two axial and radial directions of the reactor core for four fuel loading patterns. According to the results, safety margin and accelerator current ($I_e$) have been decreased in the highest case of $k_s$, but G and ${\varphi}^*$ have increased by 88.9% and 21.6%, respectively. In addition, for LP1 loading pattern, with increasing $E_e$ from 100 MeV up to 1 GeV, $Y_{n/e}$ and G improved by 91.09% and 10.21%, and $I_e$ and $P_{acc}$ decreased by 91.05% and 10.57%, respectively. The results indicate that placement of the Np-Pu assemblies on the periphery allows for a consistent $k_{eff}$ because the Np-Pu assemblies experience less burn-up.

• 한국방사선학회논문지
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• 제16권6호
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• pp.687-695
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• 2022

고 에너지 전자선 치료 시 차폐체로 사용되는 납을 대체할 수 있는 3D 프린터 소재를 찾기 위해 MCNP6 프로그램을 사용하였다. 고 에너지 전자선을 방출하는 선형가속기의 PDD(Percent Depth Dose), Flatness, Symmetry를 측정하고, MCNP6로 선형가속기를 모의 모사 후 비교하여 실측과 모의 모사와의 선원항이 일치함을 확인하였다. 납 차폐체를 모의 모사하여, 흡수선량의 95 % 이상을 차폐할 수 있는 납 차폐체의 적정 두께를 선정하였다. 3 mm 두께의 납 차폐체에 대한 흡수선량 데이터를 기준으로 하여 ABS + W(10%), ABS + Bi(10%), PLA + Fe(10%) 소재들의 1, 5, 10, 15 mm 두께 별로 모의 모사로 분석하여 차폐성능을 분석하였다. 3D 프린터로 각각의 시제품을 제작하여 모의 실험과 같은 조건으로 측정하여 분석한 결과 ABS+W(10%) 소재가 최소 10 mm 이상의 두께로 형성되었을 때, 3 mm 두께의 납을 대체할 수 있는 차폐성능을 가지는 것을 확인하였다. 주사전자현미경(SEM)과 EDS 스펙트럼을 이용하여 ABS + W(10%) 소재의 원소조성 및 표면형상을 분석하였다. 이러한 결과를 통해, 상용화 된 납 차폐체를 ABS + W(10%) 소재로 대체하면 납과 같은 차폐효과를 낼 뿐만 아니라 3D 프린터를 이용하여 환자 맞춤형으로 제작할 수 있어 고 에너지 전자선 치료에 매우 유용할 수 있음을 확인하였다.

• 한국의학물리학회지:의학물리
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• 제26권3호
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• pp.178-184
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• 2015

마커스 전리함은 치료용 전자선의 흡수선량 측정에 널리 사용되는 소형 평행 평판형 전리함이다. 특히 TRS-398 프로토콜에서는 $R_{50}<4.0g/cm^2$ (약 10 MeV 이하)에서 평행 평판형 전리함의 사용을 권고하고 있다. 그러나 TRS-398 프로토콜에서 $R_{50}<2.0g/cm^2$ (약 4 MeV 이하)에 대한 선질보정인자($k_{Q,Q_0}$)가 없어 낮은 에너지에 대한 선량측정이 필요한 경우에 마커스 전리함을 사용할 수 없다. 본 연구에서는 몬테칼로 계산(DOSRZnrc/EGSnrc)과 선량학적 계산을 이용하여 전자선 선질 $R_{50}=1.0$, 1.4, 2.0, 2.5, 3.0, $5.0g/cm^2$에 대하여 마커스 전리함(PTW-M34045)에 대한 $k_{Q,Q_0}$를 결정하였다. 본 연구에서는 결정된 $k_{Q,Q_0}$에 대해 TRS-398 및 TG-51 프로토콜의 자료와 알려진 자료들을 이용하여 평가하였다.