~(26)Al production: The Allende meteorite (Chihuahua) stellar nucleosynthesis and solar models

摘要

In 1969 a meteorite fell near the small town of Allende, state of Chihuahua in the north of Mexico. Its study yielded information that changed the current understanding of the solar model. In particular traces of ~(26)A1 were found. Abundances of that isotope had been seen in the universe and were related to regions of active heavy nucleosynthesis. Its presence on the solar system was unexpected. It is now understood that cosmic rays induce nuclear reactions on materials to produce ~(26)A1, on Earth this is well known and it is the basis of many environmental studies, so it is not only the product of some high metalicity star collapse. Taking advantage of the recently reinforced laboratory infrastructure of the Instituto de Física, at UNAM in Mexico City, we proposed to measure the cross section for ~(26)A1 production via some of the most likely reactions, from the nuclear physics point of view (highest Q-values). In this paper the study of the ~(28)Si(d,α)~(26)Al nuclear reaction is shown. A target is prepared by a mixture of silicon and aluminum powders. It is irradiated with a deuteron beam (≈1 μA current) at the 5.5 MV CN-Van de Graaff accelerator laboratory. The number of projectiles is deduced by Rutherford Backscattering Spectrometry (RBS). The produced ~(26)A1 nuclei are then counted at the Accelerator Mass Spectrometry Laboratory.