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  • Author or Editor: G. Lutz x
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Résumé  

On utilise le réaction photonucléaire204Pb(γ, n)203Pb pour doser le plomb dans des échantillons issue de milieux biologiques et de l'environment. En utilisant des échantillons déjà titrés en plomb par d'autres méthodes, on a jugé la précision des mesures convenable. En utilisant une séparation chimique soignée après l'irradiation, la quantité limite détectée est de l'ordre d'une dizaine de nanogrammes.

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Abstract  

Two-dimensional maps of half-life versus energy have been prepared for the radionuclides produced through photonuclear reactions at 30 MeV for assistance in the qualitative analysis of complex Ge(Li) spectra. The choice of nuclides for inclusion in the compilation is experimental, virtually all having been observed with a Ge(Li) detector after irradiation. Comprehensive data on relative yields at 30 MeV are also included.

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Abstract  

A large number of fragments of ancient roman pottery has been analyzed for main constituents, minor and trace-elements using high-energetic photon activation analysis followed by high resolution gamma spectroscopy. Especially the environmental influence on the concentrations of the minor constituents and trace elements during deposition of the sherds in the soil has been examined. Finally, a comparison has been made between analysis data of ancient pottery obtained by photon activation analysis, X-ray fluorescence analysis and 14 MeV-neutron activation analysis.

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Abstract  

Interfering reactions in photon activation analysis are compiled and evaluated quantitatively; the results are based on experimentally obtained data exclusively. All elements in the Periodic Table with few exceptions have been irradiated several times with 30 MeV bremsstrahlung produced by a linear electron accelerator. The element samples were measured many times to detect all expected radionuclides and hence all possible interfering reactions. These reactions are listed and presented in Table 1.

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Abstract  

Low temperature ashing is a convenient first step in many procedures of analytical chemistry as well as a potential processing method for storing environmental samples for extended periods of time. Using activation analysis, it is shown in a number of NBS Standard Reference Materials that of some 40 elements studied, the only elements observed to be lost were osmium, mercury and halogens along with carbon. No contamination during the ashing process was detected.

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Abstract  

Photon activation analysis is a suitable method for nondestructive analysis of Au, Ag and Cu because of the following advantages: the nuclear parameters (cross-sections, threshold energies) for the (γ, n)-reactions of the three elements as well as the attenuation coefficients of the activating bremsstrahlung and the emitted gamma radiation are quite similar. The severe self-shielding effects of thermal neutron activation analysis do not exist and these effects can be ignored or easily and accurately accounted for.

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Abstract  

Epithermal-neutron activation analysis (ENAA) was applied to the analysis of foods for iodine. The procedure involves irradiation of wet foods in a boron nitride, vessel, followed by direct counting of the 442.9 keV gamma ray of128I without any processing of the sample. Three research reactors were evaluated for use in determining iodine by ENAA. The University of Virginia reactor at Charlottesville was chosen for this study because the reactor facilities minimized thermal heating of the boron nitride vessel, enabling irradiation of larger, more representative analytical portions. Iodine concentrations ranging from <0.003 to 0.74 g/g are reported for 17 different food matrices.

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Abstract  

The application of high yield mass separators to problems in activation analysis is discussed. The identification of separation parameters including separator yields, memory, resolution and overlap, and sputtering are considered. The use of the mass separator in determining lead by photon activation analysis is described.

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Abstract  

Interferences of different types (competing reactions, overlapping photons emission energies etc.) occur more frequently during activation analysis with high energy exciting radiation that in conventional thermal neutron activation. Three main types of interference in high energy photon activation analysis (PAA) have been determined quantitatively, using experimentally obtained data exclusively. Based on the results presented, it is possible in many critical cases to improve significantly the accuracy of analysis results obtained by PAA.

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