[in2p3-00010207] Premières expériences de multifragmentation à l'aide du multidétecteur 4$\pi$ INDRA

This work is a contribution to the study of the formation and decay of excited nuclei produced in heavy ion collisions at intermediate energies. The experiments have been carried out at GANIL (Caen, France) with the 4π => 4π multidetector INDRA. This is a detector of charged particles and fragments with a high granularity, an excellent space coverage, low detection thresholds, and a large dynamic range in charge and in energy. The calibration of the Silicon detectors have been performed with light particles and heavy projectiles. Usual methods which calculate the pulse height defect are criticized and a new method is proposed. We also give experimental results about the charge carriers collection in partially depleted detectors. Data analysis needs a comparison between experimental results and phenomenological codes. We describe in chapter III the physical ingredients contained in two of this codes. In the last part, we show the first experimental results obtained with the Xe + Sn system, between 25 MeV/u and 50 MeV/u. Studies on fragment multiplicity distributions show that physical mechanisms with product this fragments are different from those observed at low bombarding energies.



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