Alpha particle angular distributions in reactions with weakly-bound nuclei
P. Carnelli 1*, A. Arazi 1,2, O. A. Capurro 1, M. A. Cardona 1,2, J. O. Fernández Niello 1,2, J. M. Figueira 1,2, L. Fimiani 1, D. Hojman 1,2, G. V. Martí 1, D. Martinez Heimann 1,2, A. E. Negri 1,2, A. J. Pacheco 1,2, L. Zalazar 1, W. H. Zavala Cárdenas 1
1 Laboratorio TANDAR, Comisión Nacional de Energía Atómica, Av. Gral. Paz 1499, B1650KNA, San Martín, Buenos Aires, Argentina
2 Consejo Nacional de Investigaciones Científicas y Técnicas, Av. Rivadavia 1917, C1033AAJ, Buenos Aires, Argentina
The breakup mechanism is one of the most important reaction channels when light radioactive nuclei are involved. In nuclear astrophysics, these nuclei, such as 6He, 7Be and 8Li, may constitute an alternative to the triple-alpha process in the formation of 12C. Nevertheless, these nuclei are produced in beams of very low intensities so a systematic study of their properties is difficult to carry out. Alternatively, these properties may be studied using weakly-bound, but stable,
nuclei such as 6Li, 7Li and 9Be, which can be produced in conventional accelerators with high intensity beams. Particularly, using the weakly bound projectile 7Li, there are at least three exit channels involving alpha particles: transference, fusion-evaporation and breakup. To distinguish these three processes it is helpful to determine energies, scattering angles and atomic numbers of the reaction products. With this purpose, we designed, assembled and characterized a detector-system consisting of a ionization chamber plus three position sensitive silicon-detectors (PSD). The ionization chamber delivers two partial energy-loss signals, as the three PSDs provide residual energy and scattering angle information. Given that the importance of the mentioned mechanisms depends on the scattering angle of alpha particles, we have measured the corresponding angular distributions using 7Li as a projectile and targets of 12C, 27Al and 144Sm. Beams were provided by the 20 UD TANDAR tandem accelerator with energies from 8 to 30 MeV. The covered angular range was between 15 and 140 degrees. In this contribution we present preliminary results which we hope to use, together with preexisting data for the same systems, to formulate an integral description of nuclear reactions involving the weakly-bound nucleus 7Li. Future work also implies measurements with 6Li as projectile.