• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3591-3598
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• 2023

Photoneutron background spectroscopy observations at linac are essential for directing accelerator shielding and subtracting background signals. Therefore, we constructed a Bonner Sphere Spectrometer (BSS) system based on an array of BF₃ gas proportional counter tubes. Initially, the response of the BSS system was simulated using the MCNP5 code. Next, the response of the system was calibrated by using neutrons with energies of 2.86 MeV and 14.84 MeV. Then, the system was employed to measure the spectrum of the ²⁴¹Am-Be neutron source, and the results were unfolded by using the Gravel and EM algorithms. Using the validated system, the undesirable neutron spectrum of the 120 MeV electron linac was finally measured and acquired. In addition, it is demonstrated that the equivalent undesirable neutron dose at a distance of 3.2 m from the linac is 19.7 mSv/h. The results measured by the above methods could provide guidance for linac-related research.

• 폴리머
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• 제33권3호
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• pp.263-267
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• 2009

d-PMMA(deuterated poly(methyl methacrylate)) 박막 표면의 친수성을 향상시키기 위해 산소 플라즈마에 노출시켰다. 이 때 모든 조건은 동일하며, 플라즈마에 대한 노출 시간만을 0초에서 180초까지 변화를 주어 노출 시간에 대한 영향을 접촉각과 X-ray 반사율 장치, 중성자 반사율 장치, XPS(X-ray photoelectron spectroscopy)를 이용해 조사하였다. 노출 시간이 증가할수록 물 접촉각은 작아지며, 산소의 조성은 커짐을 확인함으로써 산소의 조성이 친수성 향상에 큰 영향을 미치는 것을 확인할 수 있었다. 또한, X-ray 반사율 장치를 이용해 얻은 에칭률을 통해서 d-PMMA 박막에 대한 산소 플라즈마의 노출 시간에 따른 물리적 특성을 연구하였으며, X-ray 반사율과 중성자 반사율, 그리고 XPS 측정 결과로부터 산소와 탄소의 조성뿐만 아니라 수소의 조성까지도 얻음으로써 플라즈마 처리된 박막의 화학적 성질을 보다 자세히 연구할 수 있었다.

• Nuclear Engineering and Technology
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• 제5권3호
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• pp.191-201
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• 1973

MeV 영역의 속중성자분광을 위해 재래의 radiator system을 개량하여 ringshaped vertical radiator와 cone-shaped horizontal radiator를 공용한 특수한 recoil proton radiator assembly를 사용함으로서 energy 분해능의 저하없이 검출효율을 높이도록 recoil Proton telescope detector를 설계ㆍ제작하였다. 이 검출기에는 입사중성자속에 대한 Si(ti) 검출기의 직접노출을 피함으로서 background를 줄일수 있도록 입사중성자차폐부도 고안 내장되어 있다. 이 개량된 recoil proton telescope detector의 검출효율 및 energy 분해능을 중성자 energy 1-15 MeV에 대하여 radiator system과 Si(Li) 검출기사이의 거리변화에 따라 이론적인 계산치로 도출ㆍ표시하였으며, 실험적검증의 예로서 이 거리를 29cm로 하고 중성자 energy를 14.1 MeV로 하였을 때의 검출기의 제특성측정결과를 얻어 분석하였다. 측정결과의 분석에 의하면 이론에서 추정된것처럼 혼합형 radiator system을 사용하였을 때의 검출 효율은 단일 radiator system을 사용한 재래식 검출기의 검출효율의 2.2배의 증가를 보인데 반하여 energy 분해능의 저하는 불과 30%, background의 증가는 약40% 말만임을 알수가 있었다. 또한 측정에 의한 14.1 MeV 중성자에 대한 energy 분해능은 3.9% FWHM었는데, 이는 이논적인 3.7% FWHM와 거의 완전한 일치를 보이고 있음도 입증되였다.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4671-4677
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• 2023

For the first time Pb, Ni, and Cu nanocomposites were synthesized by versatile solution combustion synthesis using Aloevera extract as a reducing agent, to study the potential applications in X-ray/gamma, neutron, and Bremsstrahlung shielding. The synthesized Lead-Nickel-Copper (LNC) nanocomposites were characterized by PXRD, SEM, UV-VIS, and FTIR for the confirmation of successful synthesis. PXRD analysis confirmed the formation of multiphase LNC NCs and the Scherrer equation and the W-H plot gave the average crystal sizes of 19 nm and 17 nm. Surface morphology using SEM and EDX confirmed the presence of LNC NCs. Strong absorption peaks were analyzed by UV visible spectroscopy and the direct energy gap is found to be 3.083 eV. Functional groups present in the LNC NCs were analyzed by FTIR spectroscopy. X-ray/gamma radiation shielding properties were measured using NaI(Tl) detector coupled with MCA. It is found to be very close to Pb. Neutron shielding parameters were compared with traditional shielding materials and found LNC NCs are better than lead and concrete. Secondary radiation shielding known as Bremsstrahlung shielding characteristics also studied and found that LNC NCs are best in secondary radiation shielding. Hence LNC NCs find shielding applications in ionizing radiation such as X-ray/gamma and neutron radiation.

• 한국의학물리학회지:의학물리
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• 제32권4호
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• pp.145-152
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• 2021

Purpose: During the treatments of cancer patients with a linear accelerator (LINAC) using photon beams with energies ≥8 MV, the components inside the LINAC head get activated through the interaction of photonuclear reaction (γ, n) and neutron capture (n, γ). We used spectroscopy and measured the dose rate for the LINAC in operation after the treatment ended. Methods: We performed spectroscopy and dose rate measurements for three units of LINACs with a portable high-purity Germanium (HPGe) detector and a survey meter. The spectra were obtained after the beams were turned off. Spectroscopy was conducted for 3,600 seconds, and the dose rate was measured three times. We identified the radionuclides for each LINAC. Results: According to gamma spectroscopy results, most of the nuclides were short-lived radionuclides with half-lives of 100 days, except for ⁶⁰Co, ⁶⁵Zn, and ¹⁸¹W nuclides. The dose rate for three LINACs obtained immediately in front of the crosshair was in the range of 0.113 to 0.129 µSv/h. The maximum and minimum dose rates measured on weekends were 0.097 µSv/h and 0.092 µSv/h, respectively. Compared with the differences in weekday data, there was no significant difference between the data measured on Saturday and Sunday. Conclusions: Most of the detected radionuclides had half-lives <100 days, and the dose rate decreased rapidly. For equipment that primarily used energies ≤10 MV, when the equipment was transferred after at least 10 minutes after shutting it down, it is expected that there will be little effect on the workers' exposure.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1349-1354
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• 2018

Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) is widely used for the determination of trace elements in geological samples in Iran. In this paper, we have calculated the detection limits of neutron activation analysis (NAA) for some of the common elements in such samples utilizing the ORIGEN and MCNP codes and verified the simulations using the experimental results of three soil standard reference materials, namely, G02.SRM, G18.SRM, and G28.SRM. The results show that while the detection limit of ICP-AES method is usually in the mg/kg range, it is represented to the ${\mu}g/kg$ range for most of the elements of interest using the NAA method, and the simulations can be verified in a tolerance range of 20%.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.82-82
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• 2012

Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool to investigate the electronic structure of a single-crystalline solid. After the development of a two-dimensional electron detector, it became a basic experimental method in solid state physics comparable to other powerful tools such as x-ray and neutron scatterings. In this tutorial, I talk briefly on the basic principle of ARPES and its recent and future direction of development.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.1021-1030
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• 2023

We propose an overall procedure for measuring and unfolding fast neutron spectra using a trans-stilbene scintillation detector. Detector characterization was described, including the information on energy calibration, detector resolution, and nonproportionality response. The digital charge comparison method was used for the investigation of neutron-gamma Pulse Shape Discrimination (PSD). A pair of values of 600 ns pulse width and 24 ns delay time was found as the optimized conditions for PSD. A fitting technique was introduced to increase the trans-stilbene Proton Response Function (PRF) by 28% based on comparison of the simulated and experimental electron-equivalent distributions by the Cf-252 source. The detector response matrix was constructed by Monte-Carlo simulation and the spectrum unfolding was implemented using the iterative Bayesian method. The unfolding of simulated and measured spectra of Cf-252 and AmBe neutron sources indicates reliable, stable and no-bias results. The unfolding technique was also validated by the measured cosmic-ray induced neutron flux. Our approach is promising for fast neutron detection and spectroscopy.

• Nuclear Engineering and Technology
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• 제52권6호
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• pp.1252-1258
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• 2020

This study explores the ability of non-destructive assay techniques to detect a partial material defect in which 100 g of plutonium are diverted from the center of a 1000 g can of PuO₂ powder. Four safeguards measurements techniques: neutron multiplicity counting, calorimetry, gravimetry, and gamma ray spectroscopy are used in an attempt to detect the defect. Several materials are added to the partial defect PuO₂ can to replicate signatures of the diverted material. ²⁵²Cf is used to compensate for the doubles neutron counts, ²⁴¹Am is used to compensate for the decay heat, and aluminum is used to compensate for the weight. Although, the doubles and triples difference before and after diversion are statistically indistinguishable with the AWCC in fast and thermal mode, the difference in the singles counts are statistically detectable in both modes. The relatively short half-life of ²⁵²Cf leads to a decrease (three sigma uncertainty) in the doubles neutron counts after 161 days. Combining this with the precise quantity of ²⁴¹Am needed (10.7 g) to mimic the heat signature and the extreme precision in ²⁵²Cf mass needed to defeat neutron multiplicity measurements gives reassurance in the International Atomic Energy Agency's ability to detect partial material defects.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.62-66
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• 2002

The conventional floating zone(FZ) crystal and Czochralski(CZ) silicon crystal have resistivity variations longitudinally as well as radially The resistivity variations of the conventional FZ and CZ crystal are not conformed to requirement of dopant distribution for power devices and thyristors. These resistivity variations in conventional cystals limits the reverse breakdown voltage that could be achieved and forced designers of high power diodes and thyristors to compromise the desired current-voltage characteristics. So to produce high Power diodes and thyristors, Neutron Transmutation Doping(NTD) technique is the one method just because NTD silicon provides very homogeneous distribution of doping concentration. This procedure involves the nuclear transmutation of silicon to phosphorus by bombardment of neutron to the crystal according to the reaction $^{30}$ Si(n,${\gamma}$)longrightarrow$^{31}$ Silongrightarrow(2.6 hr)$^{31}$ P+$\beta$$^{[-10]}$ . The radioactive isotope $^{31}$ Si is formed by $^{31}$ Si capturing a neutron, which then decays into the stable $^{31}$ P isotope (i.e., the donor atom), whose distribution is not dependent on the crystal growth parameters. In this research, neutron was irradiated on FZ silicon wafers which had high resistivity(1000~2000 Ω cm), for 26 and 8.3hours for samples of HTS-1 and HTS-2, and 13, 3.2, 2.0 hours for samples of IP-1, IP-2 and IP-3, respectively, to compare resistivity changes due to time differences. The designed resistivities were approached, which were 2.l Ωcm for HTS-1, 7.21 Ω cm for HTS-2, 1.792cm for IP-1, 6.83 Ωcm for IP-2, 9.23 Ωcm for IP-3, respectively. Point defects were investigated with Deep Level Transient Spectroscopy(DLTS). Four different defects were observed at 80K, 125K, 230K, and above 300K.