Conférences et séminaires » Séminaire présenté par Christelle Schmitt, GANIL Cean
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Prompt γ–spectroscopy of isotopically identified fission-fragments at VAMOS++
Par : Christelle Schmitt, GANIL Cean
Date : jeudi 13 juin 2013 à 10h30
Lieu : IPHC, Salle de Réunion 2e étage du Bâtiment 27
In a single fission reaction, several hundreds of different fragments are produced. Depending on the fissioning nucleus, very neutron-rich nuclei are accessible, populated in various excited states, up to relatively high temperature and spin. Characterizing these states by prompt γ–ray spectroscopy, over the whole fragment production, enlightens our understanding of the evolution of nuclear structure as function of neutron-proton asymmetry, temperature and angular momentum. The very high discrete γ–ray density caused by the large variety of possible fission products, with often close-lying γ–ray transition energies, makes such a study experimentally very challenging. Probing the structure of a particular isotope becomes even the more difficult with increasing distance from stability. While the traditional approach uses correlations between the γ–rays emitted by complementary fission partners to ascertain the assignment of the detected photons, we report here on a new method, based on the direct detection and isotopic (Z, A) identification of the fission product γ–ray emitter, by coupling a powerful large acceptance heavy-ion spectrometer and an efficient γ–array. The technique is illustrated by a recent measurement performed at GANIL, employing the VAMOS++ spectrometer and the EXOGAM array. Fission was induced by fusion and transfer reactions in inverse kinematics with a 238U beam bombarding a 9Be target.
The achievement of the set-up regarding fragment identification will first be emphasized. The uniqueness of the technique, including high degree of selectivity and sensitivity, will further be demonstrated. The information inherent to this single data set, comprising a wealth of fragments produced simultaneously with a coherent population pattern, measured and analyzed under similar conditions, will give a comprehensive insight into the evolution of nuclear structure over a wide and exotic region of the nuclear chart. Perspectives of the method, whenever implemented at next-generation detectors and/or future facilities, will be discussed.
Personne à contacter : Kamilia SIEJA