• Journal of Radiation Protection and Research
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• 제35권2호
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• pp.85-90
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• 2010

본 연구에서는, 에너지에 따른 peak의 상대효율을 구하였으며, 검출기의 응답함수를 작성하였다. 이를 위해 고효율, 고분해능을 가진 HPGe 검출기(지름 78.7 mm, 길이 86.5 mm)를 이용하였으며 콤프턴 억제용으로 NaI 검출기를 사용하였다. 감마선 스펙트럼은 $^{23}Na$(p, $\gamma$)$^{24}Mg$ 및 $^{27}Al$(p, $\gamma$)$^{28}Si$ 반응을 이용하여 얻었으며, 이 때 입사 입자의 에너지는 각각 $E_p$ = 1424 keV 및 $E_p$ = 992 keV 이었다. 한편 스펙트럼 측정은 입사 빔 방향에 대해 $55^{\circ}$에서 하였으며, 사용한 가속기는 일본 동경공업대학의 3 MeV Pelletron 가속기를 이용하였다. 검출기의 응답함수는 1.2 MeV에서 9.4 MeV까지 0.75 MeV 간격으로 작성하였다.

• 한국방사선학회논문지
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• 제2권1호
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• pp.31-34
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• 2008

The neutron capture spectrum for the light nuclide was very useful to study the nuclear structure. In the present study, the capture gamma-ray from the 27-keV resonance of $^{19}F(n,g)^{20}F$ reaction were measured with an anti-Compton NaI(Tl) spectrometer and the 3-MV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo institute of technology. A neutron Time-of-Flight method was adopted with a 1.5 ns pulsed neutron source by the $^7Li(p,n)^7Be$ reaction. In the present experiment, a Teflon(($CF_2$)n) sample was used The sample was disk with a diameter of 90mm. The thickness of sample was determined so that reasonable counting rates could be obtained and the correction was not so large for the self-shielding and multiple scattering of neutrons in the sample, and was 5mm. The primary gamma-ray transitions were compared with previous measurement of Kenny.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.927-931
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• 2021

In this work, an attempt is made to improve the electrochemical corrosion resistance of Zircaloy-4 by helium ions implantation. For this purpose, the Zircaloy-4 was implanted with 300 keV helium ions of fluences 1 × 10¹³, 1 × 10¹⁵, and 1 × 10¹⁶ ions-cm^-2 by using Pelletron Accelerator. Electrochemical tests of pristine and ion-implanted samples were performed in NaCl solution and their potentiodynamic polarization curves were obtained. The results showed enhancement of the corrosion resistance of Zircaloy-4 after helium ions implantation. The corrosion rate and current density of the material were significantly reduced by the helium implantation. The decrease in corrosion parameters was attributed to helium ions diffusion inside Zircaloy-4 that reduced the electrons flow from the samples.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.245-246
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• 2013

한국과학기술연구원에서는 2007년부터 시작된 중대형가속기구축사업을 통하여 3기의 정전형 가속기를 설치하였다. 1996년에 도입된 2.0 MV Pelletron을 비롯하여 신규 도입된 6 MVTandetron과 400 kV implanter 등 모두 3기의 정전형가속기로 30 keV부터 ~60 MeV까지의 단색 이온빔을 인출, 이용할 수 있는 실험설비의 구축이 완성되었다. 정전형가속기의 주요 활용분야는 femto~atto mole정도의 동위원소를 측정하는 가속기질량분석법(AMS)를 비롯하여 RBS/ERD로 대표되는 이온빔분석법(ion beam analysis, IBA) 그리고 고에너지 이온빔을 이용한 물질 개질분야(ion beam material modification, IBMM)로 크게 분류된다. 이 시설은 당 연구원의 연구 수요 뿐 아니라 국내 연구자의 수요를 아우르는 시설로 계획하고 있다. 여타 실험/분석장비와 달리 가속기시설은본체의 완성 후 활용목적에 맞춰 빔라인의 증설이 필요하며 최근 가장활용성이 큰 가속기질량분석(accelerator mass spectrometry, AMS)의 경우는 활용분야별 시료 전처리 시설과 기술의 개발이 요구된다. 따라서 KIST에서는 향후 수년간 활용 분야별 대표적인 주제를 선정하고 필요한 선행연구를 통하여 KIST 이온빔시설에 대한 연구자들의 접근편의성을 제고하고자한다. 본 발표에서는 지난 6년간의 수행된 가속기 시설의 개요와 함께 장차 수행할 선행연구의 방향과 내용을 소개한다(Figure capture). Layout of the newly constructed KIST ion beam facility.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.188.1-188.1
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• 2015

For present investigation Fe/MgO/Fe/Co multilayer stack is grown on Si substrate using e-beam evaporation in ultrahigh vacuum. This stack is irradiated perpendicularly by 120 MeV $Ag^{8+}$ at different fluences ranging from $1{\times}10^{11}$ to $1{\times}10^{13}ions/cm^2$ in high vacuum using 15UD Pelletron Accelerator at Inter University Accelerator Centre, New Delhi. Magnetic measurements carried out on pre and post irradiated stacks show significant changes in the shape of perpendicular hysteresis which is relevant with previous observation of re-orientation of magnetic moment along the direction of ion trajectory. However increase in plane squareness may be due to the modification of interface structure of stacks. X-ray reflectivity measurements show onset of interface roughness and interface mixing. X-ray diffraction measurements carried out using synchrotron radiation shows amorphous nature of MgO and Co layer in the stack. Peak corresponding body centered Fe [JCPDS-06-0696] is observed in X-ray diffraction pattern of pre and post irradiated stacks. Peak broadening shows granular nature of Fe layer. Estimated crystallite size is $22{\pm}1nm$ for pre-irradiated stack. Crystallite size first increases with irradiation then decreases. Structural quality of these stacks was further studied using transmission electron microscopic measurements. Thickness from these measurements are 54, 36, 23, 58 and 3 nm respectively for MgO, Fe, MgO, Fe+Co and Au layers in the stack. These measurements envisage poor crystallinity of different layers. Interfaces are not clear which indicate mixing at interface. With increase fluence mixing and diffusion was increased in the stack. X-ray absorption spectroscopic measurements carried out on these stacks show changes of Fe valence state after irradiation along with change of O(2p)-metal (3d) hybridized state. Valence state change predicts oxide formation at interface which causes enhanced in-plane magnetization.

• 한국방사선학회논문지
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• 제1권1호
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• pp.45-49
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• 2007

동경공업대학교의 3MV 펠레트론가속기를 사용하여 10에서 90keV 영역에 대하여 $^{197}Au$의 중성자포획 스펙트럼을 측정하였다. 중성자 펄스빔은 $^7Li(p,n)^7Be$반응을 통하여 발생되었다. 사용되어진 양성자 빔의 폭은 1.5-ns였다. 금 시료에 입사된 중성자의 에너지 스펙트럼은 $^6Li$-glass 섬광검출기의 중성자 비행시간법을 사용하여 측정하였다. 금 시료의 중성자포획에 의해서 발생된 감마선은 anti-Compton NaI(TI) 검출장비를 사용하여 측정되었다. 본 연구에서는 5개의 중성자 에너지 역영을 선택했고, 각각의 에너지영역에서 얻어진 감마선파고스펙트럼을 표시하였다. 본 연구에서 얻어진 스펙트럼은 처음으로 얻어진 결과이며, 중성자 결합에너지부근에 몇 개의 천이 피크가 보인다.

• Nuclear Engineering and Technology
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• 제51권5호
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• pp.1444-1450
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• 2019

The fast-neutron shielding behaviour (FNSB) of two clay-materials (Ball clay and Kaolin)of Southwestern Nigeria ($7.49^{\circ}N$, $4.55^{\circ}E$) have been investigated using effective removal cross section, ${\Sigma}_R(cm^{-1})$, mass removal cross section, ${\Sigma}_{R/{\rho}}(cm^2g^{-1})$ and Mean free path, ${\lambda}$ (cm). These parameters decide neutron shielding behaviour of any material. A computer program - WinNC-Toolkit has been used for computation of these parameters. The toolkit evaluates these parameters by using elemental compositions and densities of samples. The proficiency of WinNC-Toolkit code was probe by using MCNPX and GEANT4 to model fast neutron transmission of the samples under narrow beam geometry, intending to represent the actual experimental setup. Direct calculation of effective removal cross section ($cm^{-1}$) of the samples was also carried out. The results from each of the methods for each types of the studied clay-materials (Ball clay and Kaolin) shows similar trend. The trend might be the fingerprint of water content retained in each of the samples being baked at different temperature. The compositions of each sample have been obtained by Particle-Induced X-ray Emission (PIXE) technique (Tandem Pelletron Accelerator: 1.7 MV, Model 5SDH). The FNSB of the selected clay-materials have been compared with standard concrete. The cognizance of various factors such as availability, thermo-chemical stability and water retaining ability by the clay-samples can be analyzed for efficacy of the material for their FNSB.