[en] The determination of beryllium by Heavy-Ion Activation Analysis (HIAA) has been studied using an oxygen-18 ion beam. 3 nuclear reactions ⁹Be(¹⁸O, 2α)¹⁹O, ⁹Be(¹⁸O,α)²³Ne, and ⁹Be(¹⁸O,d)²⁵Na have been compared. Activation curves have been established for incident beam energies ranging from 10 to 40 MeV ¹⁸O. 15 potential nuclear interfering elements, as identified with a computer program, have been systematically tested. At energies below 25 MeV only boron interferes by producing ²⁵Na, thus a very selective and sensitive determination of beryllium can be achieved using either ¹⁹O or ²⁵Na as radiotracers

[en] This presentation includes proposals for regional cooperation in Africa in the field of seismic monitoring and proposes future actions for establishing this cooperation. It emphasises the benefits of regional cooperation meaning scientific benefit from an established data base, as well as benefit in the field of geology, meteorology, geophysics and in unified budgets and logistics

[en] In order to determine traces of lithium by Heavy Ion Activation Analysis (HIAA), the yield curves and the excitation functions for 9 nuclear reactions induced by ¹⁸O ions on ⁶Li and ⁷Li, were determined in the 10 to 40 MeV energy range. The best yields were obtained with the ⁷Li(¹⁸O,αn)²⁰F and the ⁶Li(¹⁸O,2α)¹⁶N reactions. The first reaction shows a maximum cross-section of 1.02±0.09 barn for a 26 MeV ¹⁸O ion beam, thus leading to a fast, non-destructive, selective and sensitive determination of traces of lithium. (orig.)

[en] In order to determine traces of beryllium by Heavy Ion Activation Analysis (HIAA), yield curves and total cross sections for the ⁹Be(¹⁸O,2α)¹⁹O and ⁹Be(¹⁸O,d)²⁵Na reactions were determined in the 10 to 40 MeV energy range of incident ions. The yields of characteristic γ-rays (¹⁹O: Esub(γ)=197 keV and sup(i5)Na: Esub(γ)=397 keV) were used for this purpose. (orig.)

No abstract available

[en] A novel method for determining traces of sulfur and beryllium is described. The reaction ³²S(¹⁸O,t)⁴⁷V is selective if using a 39 MeV ¹⁸O⁶⁺ beam. The detection limit is 3 ppm in an iron matrix and a precision of +-15% has been achieved for samples with 15 to 20 ppm sulfur. In the case of beryllium determination, two reactions were studied, namely ⁹Be(¹⁸O,2α)¹⁹O and ⁹Be(¹⁸O,d)²⁵Na. At 25 MeV ¹⁸O⁵⁺, the first reaction is completely selective and yields a 5 ng detection limit for a 5 minutes irradiation. Boron is a nuclear interference when using the second reaction which yields a 110 ng detection limit in the same conditions. An irradiation chamber has been constructed that allows to decrease these limits. The technique was tested by analyzing two standard materials (NBS-SRM 394 and IRSID 508-1) whose sulfur content is certified. The results obtained by analyzing a biological sample (NBS-SRM 1571) for sulfur and a metallic sample Cu-Be for beryllium, are discussed