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  • Author or Editor: H. Sawahata x
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Abstract  

The spectral lines of the 478 keV prompt -ray from7*Li produced in the10B(n, )7*Li reaction were measured for a silicon wafer coated with a thin boron layer using neutron beams. The shapes of the Doppler broadened lines were found to depend greatly on the angle between the measurement axis and the boron layer surface. The angular dependence was interpreted according to whether the energetic7*Li ions are ejected into air or into the substance in the forward or backward recoil of7*Li to the -ray detector.

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Abstract  

Boron in carbonate reference samples was measured by neutron-induced prompt gamma-ray analysis (PGA) using cold and thermal neutron guide beams of the JRR-3M reactor. In order to determine B contents in marine carbonates, the Doppler-broadened -ray peak of 478 keV was used together with the correction of interference from Na-peak of 472 keV. We determined B in coral samples within 3% of analytical precision. The data obtained by the present method are mostly consistent with reported values. Here, we report PGA of B in marine carbonates.

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Abstract  

Neutron induced prompt -ray analysis (PGA) and instrumental neutron activation analysis (INAA) have been applied to the sediments collected from the Tama River estuary in Tokyo, Japan. The vertical distribution of 24 elements in the sediments was determined and the factors goveming the vertical profiles have been discussed. Major elements are distributed depending on weathering that proceeds much with increasing depth. Cadmium is highly concentrated in the deeper layer where sulphate ion is reduced to hydrogen sulphide. The distribution of several rare earth elements is also presented

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Abstract  

This paper describes effect of base profile for precise measurement of photon energy in prompt -ray analysis (PGA). The base profile has been examined in the vicinity of full energy (FE), single escape and double escape peaks. Major origins of step-wise base profiles are single and double escape events for triple photon annihilation and single and double Compton escape events for double photon annihilation in the detector, in addition to general events for the FE peak. A formula has been proposed for the quantitative characterization of the base profile.

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Abstract  

Iron and boron species in the products of thermit reaction of aluminum, iron oxide, and boron oxide were characterized by Mössbauer spectroscopy, X-ray diffraction, and prompt γ-ray analysis. It was revealed that iron and boron products of the thermit reaction are composed of intermetallic compounds with aluminum.

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Abstract  

Neutron induced prompt gamma-ray analysis (PGA) and instrumental neutron activation analysis (INAA) have been applied to the sediments collected from the Yasaka River estuary in Oita Prefecture, Japan. The vertical distribution of 33 elements in the sediments has been determined and compared with that in more polluted estuarine sediments. While the S content increased with increasing depth because of a sulphide accumulation under reducing condition, the increase in sulphide-forming elements such as Ag, Cd, Co and Zn was not observed in the deeper section of the Yasaka River estuarine sediments.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Sk. Latif, Y. Oura, M. Ebihara, G. Kallemeyn, H. Nakahara, C. Yonezawa, T. Matsue, and H. Sawahata

Abstract  

Neutron-induced prompt gamma-ray analysis (PGA) was applied to seven meteorite samples (Allende, Zagami, Acfer 209, ALH77005, ALH84001, EET79001 and Neagari). Samples were irradiated in both the thermal neutron and the cold neutron guided beams of JRR-3M at JAERI. Multiple samples of an Allende standard powder were analyzed for Si using two different methods: (1) the comparison method, using a Si standard, and (2) the mono-standard method, using Fe as an internal reference element. The Si concentrations determined by these two methods are in good agreement with literature values. The analytical sensitivity for Si using the cold neutron guided beam is∼14.3× higher than that for the thermal neutron guided beam. Other elements determined (B, Ca, Ti and S) also showed higher sensitivities using the cold neutron beam. The other meteorites studied showed some anomalous B and S values likely due to the effects of terrestrial weathering/contamination.

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Abstract  

An accurate and efficient analytical method using neutron-induced prompt γ-ray was developed for the determination of boron contents in volcanic rocks. We corrected the effect of sample geometry and flux fluctuation by using silicon as an internal standard. However, we found that the slopes of the calibration line vary among volcanic samples with different matrix. Because the increase of boron activity correlates positively with γ-ray count rate of hydrogen (water), we call this as the hydrogen effect. The hydrogen effect was confirmed by our experiment in which the boron activities showed systematic increase with the amount of added hydrogen (water). Most volcanic rocks, however, contain little water (<2 wt.%) to show this effect. We determined boron contents in various volcanic rocks in order to confirm the validity of the procedure that we established. The analyzed boron contents agreed well with the previous reported values. For efficient PGA of boron in volcanic rocks, we recommend JB-2 (GSJ standard rock) as a single geochemical standard, because of its high boron content (31.2 ppm).

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Abstract  

A permanent and stand-alone neutron-induced prompt -ray analysis (PGA) system, usable at both cold and thermal neutron beam guides of JRR-3M has been constructed. The characteristics of the system, including neutron beam and -ray spectrometer were measured. Owing to the absence of fast neutrons and the low -ray background, analytical sensitivities and detection limits better than those in other PGA systems have been achieved. Analytical results of ten elements in Standard Reference Material of Coal Fly Ash agreed well with those obtained by other methods. Isotopic analysis of Ni and its application to accurate and precise determination of Ni by stable isotope dilution method were performed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Oshima, Y. Toh, A. Kimura, M. Ebihara, Y. Oura, Y. Itoh, H. Sawahata, and M. Matsuo

Abstract  

By combining neutron activation analysis with multiple gamma-ray detection (gamma-gamma coincidence), we have proved better sensitivity and resolution for the trace element analysis than the ordinary single gamma-ray detection method. We now try to apply the multiple gamma-ray detection method to the prompt gamma ray analysis (PGA). We have established a new cold neutron beam line for PGA in Japan Research Reactor, JRR-3M, at Tokai establishment of Japan Atomic Energy Research Institute (JAERI). It consists of a beam shutter, a beam attenuator, a gamma-ray detector array, a sample changer, and a beam stopper. We construct a high-efficiency gamma-ray detector array specially designed for this purpose. Its performance has been evaluated with the Monte Carlo simulation code, GEANT 4.5.0.

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