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A high-energy mass spectrometer based on the XTU Tandem accelerator of the Laboratori Nazionali di Legnaro is described. Preliminary measurements on standard samples with known10Be/9Be atom ratio show the capability of the system to measure natural concentrations of10Be for geological and cosmochronological studies. The modifications necessary to improve sensitivity and precision of the measurements are discussed.

A variable cosmogenic-production rate model is proposed which takes account of the changes in galactic-cosmic-ray irradiation conditions arising from the vertical oscillation of the solar system about the galactic plane. The model incorporates and substantiates several ideas and suggestions previously put forward in the literature. The time distribution of the10Be concentration predicted by the model appears to be consistent with the data of the deep-sea sediment core RC 12-65. A comparison of our model with the conventional constant-production rate model is carried out, especially with reference to time-integrated concentrations in meteorites.

An easy and rapid method for preparing biological targets for trace element analysis using nuclear techniques involving charged particle beams is described. The targets are thin, homogeneous and uniform. They withstand 100 nA of 1–2 MeV proton beams and of 5–10 MeV alpha beams for about 10 hrs.

A study of neutron and gamma interaction (in the low dose range) with L-phenylalanine in aqueous solutions shows that the main radiolytic pathway occurs through the attack of OH radicals. The products of the interaction are essentially tyrosine, Dopa and melanine in both cases. However, for gamma radiation there is a complete utilization of the OH radicals and the reaction pathway mainly proceeds by the sequence: phenylalanine»tyrosine»Dopa»melanine. On the contrary, for neutron radiation, the OH recombination is a rather efficient process and the prevailing pathway is: phenylalanine»Dopa»melanine.