Formation et désexcitation des noyaux chauds dans les réactions induites par des faisceaux de protons (475 MeV et 2 GeV) et d'$^{3}$He (2 GeV)

Abstract : We are studying the formation and the de-excitation of hot nuclei created in reactions induced by light high energy projectiles. These reactions, described in a two step model: an intranuclear cascade followed by an evaporation phase, produce nuclei in which the collective modes (compression, rotation, deformation) are weakly excited. By measuring the neutron multiplicities, event by event with ORION, and the light charged particle energies and multiplicities one can evaluate the excitation energy distribution of the nuclei. At the same time, theoretical simulations are carried out using the intranuclear cascade code developed by J. Cugnon and the statistical de-excitation code GEMINI. The good agreement with experimental results indicate that 10% of the p-nucleus interactions lead to temperatures greater than 5 MeV. The observation of the fission of a nucleus with a temperature close to 5 MeV shows that the nucleus behaves as a set of bound nucleons and, that the temperature stability limit is not yet reached. The observed decline of fission probability at high excitation energies is most likely to be correlated to the appearance of an other de-excitation process (evaporation residues emission or multifragmentation) which could not be experimentally detected. Finally, in the last chapter, we briefly present the principle of transmutation for long-lived nuclear waste with a proton accelerator and underline the interest of the present work in such studies.
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X. Ledoux. Formation et désexcitation des noyaux chauds dans les réactions induites par des faisceaux de protons (475 MeV et 2 GeV) et d'$^{3}$He (2 GeV). Physique Nucléaire Expérimentale [nucl-ex]. Université de Caen, 1995. Français. ⟨in2p3-00010209⟩

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