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RISS 인기검색어
- 검색키워드
- 발행기관 : North-Holland Physics Pub (검색결과 5 건)
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Mokhtari Oranj, L.,Jung, N.S.,Oh, J.H.,Lee, H.S. North-Holland Physics Pub 2016 Nuclear instruments & methods in physics research. Vol.375 No.-
The proton beam intensity of a 100-MeV proton linac at the Korea Multi-purpose Accelerator Complex (KOMAC) was measured by an Au activation analysis using <SUP>197</SUP>Au(p,pn)<SUP>196</SUP>Au and <SUP>197</SUP>Au(p,p3n)<SUP>194</SUP>Au reactions to determine the accuracy and precision of beam intensity measurement using Gafchromic film dosimetry method. The target, irradiated by 100-MeV protons, was arranged in a stack consisting of Au, Al foils and Pb plates. The yields of produced radio-nuclei in Au foils were obtained by gamma-ray spectroscopy. The FLUKA code was employed to calculate the energy spectrum of protons onto the front surface of Au foils located at three different depth points of the target and also to investigate the condition of incident beam on the target. A good agreement was found between the beam intensity measurements using the activation analysis method at three different depth points of the target. An excellent agreement was also observed between the beam intensity measurements using the Au activation analysis method and the dosimetry method using Gafchromic film.
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Spectroscopic study of energetic helium-ion irradiation effects on nuclear graphite tiles
Kim, D.W.,Lee, K.W.,Choi, D.M.,Noh, S.J.,Kim, H.S.,Lee, C.E. North-Holland Physics Pub 2016 Nuclear instruments & methods in physics research. Vol.368 No.-
Helium ion-irradiation effects on the nuclear graphite tiles were studied in order to understand the structural modifications and damages that can be produced by fusion reaction in tokamaks. The surface morphological changes due to increasing dose of the irradiation were examined by the field-effect scanning electron microscopy, and X-ray photoelectron spectroscopy elucidated the changes in the shallow surface bonding configurations caused by the energetic irradiation. Raman spectroscopy revealed the structural defects and diamond-like carbon sites that increased with increasing irradiation dose, and the average inter-defect distance was found from the Raman peak intensities as a function of the irradiation dose.
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Rahman, Md.S.,Shaislamov, U.,Yang, J.K.,Kim, J.K.,Yu, Y.H.,Choi, S.,Lee, H.J. North-Holland Physics Pub 2016 Nuclear instruments & methods in physics research. Vol.387 No.-
Polyoxymethylene copolymer (POM-C) is an attractive and widely used engineering thermoplastic across many industrial sectors owing to outstanding physical, mechanical, self-lubricating and chemical properties. In this research work, the POM-C blocks were irradiated with 1MeV electron beam energy in five doses (100, 200, 300, 500 and 700kGy) in vacuum condition at room temperature. The tribological and physico-chemical properties of electron beam irradiated POM-C blocks have been analyzed using pin on disk tribometer, Raman spectroscopy, FTIR-ATR, gel content analysis, SEM-EDS (scanning electron microscopy-energy dispersive spectroscopy), surface profiler and contact angle analyzer. Electron beam irradiation at a dose of 100kGy resulted in decrease of the friction coefficient of POM-C block due to well suited carbonization, cross-linking, free radicals formation and partial physical modification. It also showed the lowest surface roughness and highest water contact angle among all unirradiated and irradiated POM-C blocks. The irradiation dose at 200kGy resulted in increase of friction coefficient due to less effective cross-linking, but the irradiation doses at 300, 500 and 700kGy resulted in increase of the friction coefficient as compared to unirradiated POM-C block due to severe chain scission, chemical and physical structural degradation. The degree of improvement for tribological attribute relies on the electron beam surface dose delivered (energy and dose rate).
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Kajimoto, T.,Shigyo, N.,Sanami, T.,Iwamoto, Y.,Hagiwara, M.,Lee, H.S.,Soha, A.,Ramberg, E.,Coleman, R.,Jensen, D.,Leveling, A.,Mokhov, N.V.,Boehnlein, D.,Vaziri, K.,Sakamoto, Y.,Ishibashi, K.,Nakashim North-Holland Physics Pub 2014 Nuclear instruments & methods in physics research. Vol.337 No.-
The energy spectra of neutrons were measured by a time-of-flight method for 120GeV protons on thick graphite, aluminum, copper, and tungsten targets with an NE213 scintillator at the Fermilab Test Beam Facility. Neutron energy spectra were obtained between 25 and 3000MeV at emission angles of 30<SUP>o</SUP>, 45<SUP>o</SUP>, 120<SUP>o</SUP>, and 150<SUP>o</SUP>. The spectra were parameterized as neutron emissions from three moving sources and then compared with theoretical spectra calculated by PHITS and FLUKA codes. The yields of the theoretical spectra were substantially underestimated compared with the yields of measured spectra. The integrated neutron yields from 25 to 3000MeV calculated with PHITS code were 16-36% of the experimental yields and those calculated with FLUKA code were 26-57% of the experimental yields for all targets and emission angles.
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Moon, B.S.,Lee, H.J.,Lee, W.K.,Hur, M.G.,Yang, S.D.,Lee, B.C.,Kim, S.E. North-Holland Physics Pub 2015 Nuclear instruments & methods in physics research. Vol.356 No.-
The KOTRON-13 cyclotron, which was developed in South Korea for the production of medical radioisotopes, has the structural limitation of only one beam-output port, restricting the production of the carbon-11 isotope. In the present study, we investigate the design of a switchable target system and develop an effective carbon-11 target in the KOTRON-13 cyclotron, for combination with the fluorine-18 target. The target system was designed by introducing a sliding-type element between the fluorine-18 and carbon-11 targets, a tailor-made C-11 target and its cooling system. For the efficient production of [<SUP>11</SUP>C]CO<SUB>2</SUB>, the desirable target shape and internal volume were determined by a Stopping and Range of Ions in Matter (SRIM) simulation program, and the target grid was modified to resist the cavity pressure during beam irradiation. We evaluated the [<SUP>11</SUP>C]CO<SUB>2</SUB> production while varying the material and thickness of the target foil, oxygen content of the nitrogen gas, and target loading pressure. Using sliding-type equipment including an additional gate valve and a high vacuum in a beam line, the bi-directional conversion between the fluorine-18 and carbon-11 targets was efficient regarding the accurate beam irradiation on both targets. The optimal [<SUP>11</SUP>C]CO<SUB>2</SUB> production for 30min irradiation at 60μA (86.6+/-1.7GBq in the target at EOB) was observed at a thickness of 19μm with HAVAR® material as a target foil and a target loading pressure of 24bar with nitrogen plus 300ppb of oxygen gas. Additionally, the coolant cavity system in the target grid and target chamber is useful to remove the heat transferred to the target body by the internal convection of water and thereby ensure the stability of the [<SUP>11</SUP>C]CO<SUB>2</SUB> production under a high beam current. In the application of C-11 labeled radiopharmaceuticals such as [<SUP>11</SUP>C]PIB, [<SUP>11</SUP>C]DASB, [<SUP>11</SUP>C]PBR28, [<SUP>11</SUP>C]Methionine and [<SUP>11</SUP>C]Clozapine, the radiochemical yields were shown to be 25-38% (decay corrected) with over 166GBq/μmol of specific activity. Consequently, the additive carbon-11 target system was successfully developed in only one output port of the KOTRON-13 cyclotron and exhibited the stable production of C-11 labeled radiopharmaceuticals.
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