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RISS 인기검색어
- 검색키워드
- 저자 : ( Fumitaka Esaka ) (검색결과 5 건)
- 무료
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Esaka, Fumitaka,Magara, Masaaki,Suzuki, Daisuke,Miyamoto, Yutaka,Lee, Chi-Gyu,Kimura, Takaumi Korean Society for Mass Spectrometry 2011 Mass spectrometry letters Vol.2 No.4
Isotope ratio analysis of nuclear materials in individual particles is of great importance for nuclear safeguards. Although secondary ion mass spectrometry (SIMS) and thermal ionization mass spectrometry (TIMS) are utilized for the analysis of individual uranium particles, few studies were conducted for the analysis of individual uranium-plutonium mixed oxide particles. In this study, we applied SIMS and inductively coupled plasma mass spectrometry (ICP-MS) to the isotope ratio analysis of individual U-Pu mixed oxide particles. In the analysis of individual U-Pu particles prepared from mixed solution of uranium and plutonium standard reference materials, accurate $^{235}U/^{238}U$, $^{240}Pu/^{239}Pu$ and $^{242}Pu/^{239}Pu$ isotope ratios were obtained with both methods. However, accurate analysis of $^{241}Pu/^{239}Pu$ isotope ratio was impossible, due to the interference of the $^{241}Am$ peak to the $^{241}Pu$ peak. In addition, it was indicated that the interference of the $^{238}UH$ peak to the $^{239}Pu$ peak has a possibility to prevent accurate analysis of plutonium isotope ratios. These problems would be avoided by a combination of ICP-MS and chemical separation of uranium, plutonium and americium in individual U-Pu particles.
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Esaka, Fumitaka,Magara, Masaaki Korean Society for Mass Spectrometry 2016 Mass spectrometry letters Vol.7 No.2
Secondary ion mass spectrometry (SIMS) is a promising tool to measure isotope ratios of individual uranium particles in environmental samples for nuclear safeguards. However, the analysis requires prior identification of a small number of uranium particles that coexist with a large number of other particles without uranium. In the present study, this identification was performed by scanning electron microscopy - energy dispersive X-ray analysis with automated particle search mode. The analytical results for an environmental sample taken at a nuclear facility indicated that the observation of backscattered electron images with × 1000 magnification was appropriate to efficiently identify uranium particles. Lower magnification (less than × 500) made it difficult to detect smaller particles of approximately 1 μm diameter. After identification, each particle was manipulated and transferred for subsequent isotope ratio analysis by SIMS. Consequently, the isotope ratios of individual uranium particles were successfully determined without any molecular ion interference. It was demonstrated that the proposed technique provides a powerful tool to measure individual particles not only for nuclear safeguards but also for environmental sciences.
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( Fumitaka Esaka ),( Masaaki Magara ),( Daisuke Suzuki ),( Yutaka Miyamoto ),( Chi-gyu Lee ),( Takaumi Kimura ) 한국질량분석학회 2011 Mass spectrometry letters Vol.2 No.4
Isotope ratio analysis of nuclear materials in individual particles is of great importance for nuclear safeguards. Although secondary ion mass spectrometry (SIMS) and thermal ionization mass spectrometry (TIMS) are utilized for the analysis of individual uranium particles, few studies were conducted for the analysis of individual uranium-plutonium mixed oxide particles. In this study, we applied SIMS and inductively coupled plasma mass spectrometry (ICP-MS) to the isotope ratio analysis of individual U-Pu mixed oxide particles. In the analysis of individual U-Pu particles prepared from mixed solution of uranium and plutonium standard reference materials, accurate 235U/238U, 240Pu/239Pu and 242Pu/239Pu isotope ratios were obtained with both methods. However, accurate analysis of 241Pu/239Pu isotope ratio was impossible, due to the interference of the 241Am peak to the 241Pu peak. In addition, it was indicated that the interference of the 238UH peak to the 239Pu peak has a possibility to prevent accurate analysis of plutonium isotope ratios. These problems would be avoided by a combination of ICP-MS and chemical separation of uranium, plutonium and americium in individual U-Pu particles.
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( Fumitaka Esaka ),( Masaaki Magara ) 한국질량분석학회 2016 Mass spectrometry letters Vol.7 No.2
Secondary ion mass spectrometry (SIMS) is a promising tool to measure isotope ratios of individual uranium particles in environmental samples for nuclear safeguards. However, the analysis requires prior identification of a small number of uranium particles that coexist with a large number of other particles without uranium. In the present study, this identification was performed by scanning electron microscopy - energy dispersive X ray analysis with automated particle search mode. The analytical results for an environmental sample taken at a nuclear facility indicated that the observation of backscattered electron images with × 1000 magnification was appropriate to efficiently identify uranium particles. Lower magnification (less than × 500) made it difficult to detect smaller particles of approximately 1 μm diameter. After identification, each particle was manipulated and transferred for subsequent isotope ratio analysis by SIMS. Consequently, the isotope ratios of individual uranium particles were successfully determined without any molecular ion interference. It was demonstrated that the proposed technique provides a powerful tool to measure individual particles not only for nuclear safeguards but also for environmental sciences.
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Yamada, Yoichi,Kuklin, Artem V.,Sato, Sho,Esaka, Fumitaka,Sumi, Naoto,Zhang, Chunyang,Sasaki, Masahiro,Kwon, Eunsung,Kasama, Yukihiko,Avramov, Pavel V.,Sakai, Seiji Elsevier 2018 Carbon Vol.133 No.-
<P><B>Abstract</B></P> <P>We report the scanning tunneling microscope (STM) observation of the Li<SUP>+</SUP> ion endohedral C<SUB>60</SUB> on Cu(111), prepared by means of evaporation of a high-purity Li<SUP>+</SUP>@C<SUB>60</SUB>[PF<SUB>6</SUB> <SUP>−</SUP>] salt. The electronic state of Li<SUP>+</SUP>@C<SUB>60</SUB> in the Li<SUP>+</SUP>@C<SUB>60</SUB>[PF<SUB>6</SUB> <SUP>−</SUP>] salt was also determined using photoemission and X-ray absorption spectroscopy, along with the density functional theory (DFT) calculations. In the salt, Li and PF<SUB>6</SUB> had nearly single positive and negative charge, respectively; thus the C<SUB>60</SUB> cage was practically neutral. The salt decomposed under ultra-high vacuum while heating at 400 °C. This allowed the selective deposition of Li<SUP>+</SUP>@C<SUB>60</SUB> on Cu(111). Although secondary-ion mass spectroscopy of the deposited Li<SUP>+</SUP>@C<SUB>60</SUB> film showed a decrease in the Li-content during evaporation, Li<SUP>+</SUP>@C<SUB>60</SUB> was successfully identified using STM. The DFT calculations of Li<SUP>+</SUP>@C<SUB>60</SUB> on Cu(111) suggested that the Li<SUP>+</SUP> ion was singly charged and the location of the Li<SUP>+</SUP> ion was displaced in an upward direction, which altered the local density of states in an upper section of C<SUB>60</SUB>, especially for LUMO+2. The calculated results were mostly in agreement with the bias-dependent STM and dI/dV images. However, an inconsistency was observed between the calculation and experiments in case of empty state imaging where tip-induced displacement of the Li<SUP>+</SUP> ion may occur.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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