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  • Author or Editor: M. Koizumi x
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Abstract  

In order to improve the limits of quantification for trace elements, we applied the multiple gamma-ray detection method in the prompt gamma-ray analysis (PGA). The Clover Ge detector system was constructed for multiple prompt gamma-ray analysis (MPGA) at the neutron guide hall of the JRR-3M reactor of the Japan Atomic Energy Agency (JAEA). The MPGA system consists of three Clover detectors and a BGO Compton suppressor. The instrumentation of the MPGA beam line and the detector system were developed. The estimated limit of quantification of cadmium in the plastic sample is approximately 0.1 ppm. The capability of the MPGA system could be improved by modification of the detector system, shield arrangement, software algorithm, etc.

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Abstract  

The interactions of benzalkonium chloride (BC)with components of stratum corneum, a model system of intercellular lipids in human stratum corneum and homogenized rat stratum corneum were characterized in terms of thermodynamics at pH 7.5 and 37C. BC was strongly bound to cholesterol and cholesterol sulfate with higher affinities (105~106 M-1) than to any other components of the stratum corneum by hydrophobic interaction and ionic interaction, respectively. BC binding to the model system of intercellular lipids significantly decreased only in the absence of cholesterol. It is indicated that cholesterol and its derivatives play an important role in the penetration and/or accumulation of BC in stratum corneum.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Oshima, Y. Toh, Y. Hatsukawa, M. Koizumi, A. Kimura, A. Haraga, M. Ebihara, and K. Sushida

Abstract  

A new radionuclide quantification method is proposed on the basis of multiple gamma-ray detection, which is two or higher fold gamma-ray coincidence method. The coincidence method has so far been used for nuclear structure study. We apply this method for quantification of radioactive nuclei. The advantage of this method consists of high energy resolution and high sensitivity. It is successfully applied to nuclear waste analysis, neutron activation analysis and prompt gamma-ray analysis. The principle of the multiple gamma-ray detection method and future perspectives for an innovative pulsed neutron source and a new detector system will be presented.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Y. Toh, M. Koizumi, M. Oshima, A. Kimura, Y. Hatsukawa, A. Osa, and J. Goto

Abstract  

In order to improve the sensitivity for the quantification of trace elements, we propose the combination of prompt gamma-ray analysis (PGA) and a multiple gamma-ray detection method. A new Ge detector system for multiple prompt gamma-ray analysis (MPGA) was constructed at the neutron guide-hall of the JRR-3M reactor of the Japan Atomic Energy Agency (JAEA). The first demonstration of this system was given with a plastic sample containing traces of cadmium. The quantification limit of cadmium in a plastic sample was found to be about 0.1 ppm.

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Abstract  

Low-energy photons produced by the Compton scattering from hydrogen increase the background in the lower-energy region of the gamma-ray spectrum. This results in an increase in the detection limit for trace elements. In multiple photon detection prompt gamma-ray analysis (MPGA), only those elements that simultaneously emit two or more prompt gamma-rays, which have cascade relation and are emitted within a short interval, can be measured. Therefore, the influence of hydrogen can be reduced. In this study, standard polymer and food samples are measured. The hydrogen background is reduced in MPGA.

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Abstract  

A neutron beam line for multiple prompt gamma-ray analysis was constructed at the Japan Atomic Energy Agency. A detector system for the MPGA was constructed at the C2-3-2 beam line in January 2005. It comprised eight (upgraded in March 2007) clover Ge detectors with a BGO Compton suppressor. High efficiency detector system provides an advantage in terms of the detection limit of MPGA when compared to the result of PGA. The supermirror neutron bender was improved and a supermirror neutron guide was installed upstream of the sample position.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Watanabe, N. Ishioka, T. Sekine, A. Osa, M. Koizumi, H. Shimomura, K. Yoshikawa, and H. Muramatsu

Abstract  

Ion implantation was applied to the production of endohedral 133Xe-fullerene. Using an isotope separator, 133Xe ions were implanted into a fullerene target of C60 and C70 produced by vacuum evaporation on a Ni backing. An HPLC analysis following dissolution of the fullerene targets in o-dichlorobenzene corroborated the formation of 133Xe@C60 and 133Xe@C70, showing a strong correlation between C60/C70 and 133Xe. The observed tailing following 133Xe peaks in the elution curves suggests a possibility of the isolation of endohedral 133Xe-fullerene from empty fullerene.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: N. Shigeta, H. Matsuoka, A. Osa, M. Koizumi, M. Izumo, K. Kobayashi, K. Hashimoto, T. Sekine, and R. Lambrecht

Abstract  

No-Carrier-Added186Re was produced using the186W(p,n)186Re nuclear reaction with 13.6 MeV protons on thick targets of 99.79% isotopically enriched186WO3. The theoretical excitation functions for producing186Re, and possible radionuclidic impurities of182Re,183Re, and184Re were calculated using the ALICE code. Cross-sections of the186W(p,n)186Re reaction were measured up to 20 MeV using the stacked target method with thin foils of natural composition tungsten metal. The experimental and theoretical excitation functions were in good agreement. Targetry used at the TIARA cyclotron, and a radiochemical separation scheme for186Re are described.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: H. Muramatsu, H. Ishii, E. Tanaka, M. Misawa, H. Ito, T. Miura, S. Muto, M. Koizumi, A. Osa, T. Sekine, and M. Yanaga

Abstract  

Mössbauer effect measurements for the 81 keV transition in133Cs have been performed with133Xe-implanted sources prepared by means of an electromagnetic isotope separator. The behavior of the isomer shift of133Cs impurities was studied in various metals. Some correlations were found between measured isomer shifts and electronic properties of the host materials, and they show that the host conduction electrons have an important role in the determination of the isomer shift in metals.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Y. Oura, R. Watanabe, M. Ebihara, Y. Murakami, Y. Toh, A. Kimura, M. Koizumi, K. Furutaka, M. Oshima, K. Hara, T. Kin, S. Nakamura, and H. Harada

Abstract  

A prompt gamma-ray analysis system using multiple detection method (MPGA system) was constructed at the neutron guide hall of the JRR-3M reactor of the Japan Atomic Energy Agency. We applied MPGA method to geochemical and cosmochemical samples to evaluate its analytical performance on signal to noise (S/N) ratio, sensitivity, and detection limit. The S/N ratio measured by MPGA system was larger than that by normal prompt gamma ray activation analysis (PGAA) at JRR-3M. For some elements, the S/N ratio was improved more than ten times. Several elements that are not detected by PGAA were detected by MPGA. At the present time, concentrations of major elements and trace elements with high neutron capture cross section in geochemical and cosmochemical samples were determined accurately by the MPGA system installed at JRR-3M. It is expected that it will determine a lot of trace elements after appropriate adjustments and modifications.

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