Recherche de la symétrie tétraédrique dans le noyau 156Gd par spectroscopie γ, Search for tetrahedral in 156Gd nucleus by gamma-ray spectroscopy

Quang Tuyen Doan

Description

Sous la direction de Olivier Stezowski
Thèse soutenue le 26 novembre 2009: Lyon 1
Des calculs théoriques utilisant la méthode de champ moyen ont suggérée l'existence des formes du noyau avec la symétrie tétraédrique et/ou octraédrique dans la région des terres rares au voisinage des noyaux 156Gd et 160Yb. Dans les noyaux avec une symétrie tétraédrique pure, des transitions intra-bande E2 à bas spin dans des bandes de parité négative disparaissent ou sont très faibles. Ce travail est dédié à une recherche expérimentale de la symétrie tétraédrique dans le noyau 156Gd. Une expérience a été faite à Jyväskylä avec le multi-détecteur JUROGAM, sur la réaction de fusion - évaporation 154Sm(, 2n)156Gd. L'analyse des données, a établi les rapports d'embranchement de deux bandes de parité négative et a permis, par distribution angulaire, de connaître la nature d'une nouvelle transition. Les rapports d'embranchement obtenus sont comparables avec ceux des expériences précédentes et quelques limites supérieures ont été déterminées. L'absence de transitions à bas spin (I$^{pi}<9$) dans la bande de parité négative à spin impair a été confirmée. Ces résultats ont renforcé l'hypothèse d'une symétrie tétraédrique dans le noyau 156Gd. La spectroscopie gamma est l'outil majeure utilisé dans ce travail. Les principes ainsi qu'une étude de simulation réaliste sont détaillés dans ce manuscrit. La simulation avec des événements réalistes a été faite pour comparer la fonction de réponse de deux types de multidétecteurs EUROBALL et AGATA. Les résultats montrent que sous certain conditions la phase démonstrateur d'AGATA peut être utilisée pour la recherche d'événements rares.
-Spectroscopie gamma
-Euroball
-Simulation
-Superdéformation
-Symétrie tétraédrique
-Analyses des données
-Structure nucléaire
-TetraNUC
Theoretical calculations using realistic mean-eld method suggest the existence of nuclear shapes with tetrahedral and/or octahedral symmetries in some rare earth nuclei around 156Gd and 160Yb. In nuclei with exact tetrahedral symmetry, the E2 intra-band transitions are predicted to vanish completely or to be very weak. This work is devoted to an experimental research of the tetrahedral symmetry in the nucleus 156Gd. An experiment has been carried out with the JUROGAM - rays detector at Jyväskylä by using the fusion - evaporation reaction 154Sm(, 2n)156Gd. In analysis, the branching ratios of two parity negative bands were determined, the angular distribution has been analyzed to determine the nature of one inter-band transition between these two bands. The transitions strength ratios determined are of the same order of magnitude as previous experiments, and some upper limits have been established for the lowest spin. The missing of the E2 transitions below the (I$^{pi}<9$)states in the odd spin parity negative band were conrmed. The results of this work reinforced the hypothesis of the tetrahedral symmetry in the nucleus 156Gd. -ray spectroscopy is the major tool used for this work. Detection principles and -ray simulations are detailed in the document. The simulation, based on realistic events, has been realised to compare the response function of two multidetectors EUROBALL and AGATA. The results show that under certain conditions the rst phase of AGATA (demonstrator) is also a tool to search for rare events
-Gamma-ray spectroscopy
-Euroball
-Nuclear structure
Source: http://www.theses.fr/2009LYO10202/document

Sujets

• Simulation
• Structure nucléaire

Informations

• Publié par: Thesee
• Nombre de lectures: 44
• Langue: Français
• Poids de l'ouvrage: 8 Mo

Extrait

Nd’ordre 202-2009
LYCEN - .....
These
presentee
devant l’Universite Claude Bernard Lyon-1
pour l’obtention du
DIPLOME de DOCTORAT
(arr^ete du 07 aout^ 2006)
Specialite : Physique Nucleaire
par
DOAN Quang Tuyen
Recherche de la symetrie tetraedrique dans le
156noyau Gd par spectroscopie
soutenue le 26 Novembre 2009
devant la Commission d’Examen
Jury : M. D. CURIEN
M. D. DAVESNE
M. D. GUINET
Mme. A. KORICHI Rapporteur
M. C. PETRACHE Rapp et President du Jury
M. O. STEZOWSKI Directeur de these
Institut de Physique Nucleaire de Lyon
43, Bd du 11 Novembre 1918
69622 Villeurbanne Cedex, France
tel-00561660, version 1 - 1 Feb 2011tel-00561660, version 1 - 1 Feb 2011TetraNUC AGATA
Bernard ILLE
IPNLyon
Olivier STEZOWSKI
CNRS
Daniel GUINET
Daniel
Costel PETRACHE
Amel KORICHI, CSNSM
CNRS
Dany DAVESNE
Dominique CURIEN IPHC
?d?e?n?o?m?b?r?e?u?s?e???r?e?n?c?o?n?t?r?e??.J?e?s?u?g?g?e?s?t?i?o?n???q?u?'?i?l?r?a?p?p?o?r?t?e?u?r??v?o?u?d?r?a?i???l?e?r?e?m?e?r?c?i?e?r??d?e?i?c?i???t?o?u?t?e???a?u?q?u?e?l?l?e???e?t?p?e?r?s?o?n?n?e???p?r???s?i?d?e?r??q??e?tuP??p?o?u?r?i?l?e??m?o?t?i?v?a?t?i?o?n??o?n?t?e?x?p?r?i?m?e?r??c?o?n?t?r?i?b?u???e??e?r?s?i?t???d?e?e?t?p?r????????o?u?D?i?r?i?g???d?en?l?o?i?n??g?r?a?t?i?t?u?d?e????y?o?n??l??a?b?o?u?t?i?s?s?e?m?e?n?t???g?a?l?e?m?e?n?t?d?e?l?e???c?e?a?n?n???e??.?t?r?a?v?a?i?l.?d?u?T?o?u?tv???d?'?a?b?o?r?d?,?e?t?j?e?s?t?r?u?c?t?u?r?e?v?o?u?d?r?a?i??????r?e?m?e?r?c?i?e?r?o?f?e?s?s?e?u?r?M?o?n?s?i?e?u?r?1,?e?u??p?o?r?t?e?r??j'?a?i??d?'???t?r?e?t?h???s?e,?c?e?t?t?e,?g?r?a?t?i?t?u?d?eD?i?r?e?c?t?e?u?r?D?o?c?t?e?u?r??d?u??d?e?l?a?b?o?r?a?t?o?i?r?e?l??p?o?u?r???m?'?a?v?o?i?r?J'?a?i?m?e?r?a?i???a?c?c?u?e?i?l?l?i??d?e?a?u??l?U?s?e?i?n??a?c?c?e?p?t???d?e?d?e?d?e?r?a?t?i?o?n??.?d?i?s?c?u??-J?e?e?t?v?o?u?d?r?a?i???c?e???e?x?p?r?i?m?e?r??c?h?a?n?c?e?e?n??d?e?c?e???o?y?a?u??q?u?e?l?q?u?e???t?r?o?l?i?g?n?e???t?r?????t?o?u?t?e?l?a??m?a??p?a?r?t?i?c?u?l?i???r?e?m?e?n?t?g?r?a?t?i?t?u?d?e?d?e?e?tJ?e?t?o?u?t?e?r?e?c?o?n?n?a?i??m?a??l?a??r?e?c?o?n?n?a?i?s?s?a?n?c?eP????l?U?m?o?n??a?r?i??-S?u?d??d?i?r?e?c?t?e?u?r??l??d??b?i?e?n?e?c?e?t?h???a?v?o?i?r??s?e?t?e?j?u?r?y,J?eM?o?n?s?i?e?u?r??t?o?u?t?e?a?n?n???e??)??l?e?r??t?r?o?i??a?b?i?l?i?t???c?e??R?e?c?h?e?r?c?h?e??,?d?e?e,?m?'?a?v?o?i?r??g?r?o?u?p?eh?o?nM?a?t?i???r?e?N?u?c?l???a?i?r?e,?d?'???t?r?eD?o?c?t?e?u?r??c?e?t?t?eH?t?o?u?t?e?a?b?i?l?i?t??M?o?n?s?i?e?u?r????(D?i?r?i?g???s?e?u?r??d?e??e?r?s?i?t??R?e?c?p?o?u?r??h?e?r?c?h?e??,?f?a?i?r?e?c?h?a?r?g???m?o?n??d?eJ?e?r?e?c?h?e?r?c?h?r?e?m?e?r?c?i?e?r??e?t?h???s?e,?a?u??l?e???c?o?u?r???s?i?o?n??,.?c?o?n?s?e?i?l??A?u??l?e???l?o?n?g?p?e?n?d?a?n?t?d?e?t?r?o?i???c?e??M?e?r?c?i??t?r?o?i???p?o?u?r??a?n?n???e???c?o?u?r???d?eP?h?y?s?i?q?u?e?t?h???s?e,N?j'?a?i??g?r???c?e?p?u??j'?a?i???u?a?p?p?r???c?i?e?r??u?n?e?s?o?n??f?o?r?t?e???n?e?r?g?i?e,?p?o?u?r??s?e???r?e?c?h?e?r?c?h?e?g?r?a?n?d?e???p?l?u???c?o?m?p???t?e?n?c?e???d?a?n???s?c?i?e?n?t?i?f?i?q?u?e???d?o?m?a?i?n?e?e?t?l?a??c?o?m?p?t?e?r??n?u?c?l???a?i?r?e.?s?u?r??s?o?u?h?a?i?t?e?s?o?n??m?a??s?o?u?t?i?e?n?.s?s?a?n?c?eLM?o?n?s?i?e?u?r??e???e?u??n?o?m?b?r?e?u?x,?c?o?n?s?e?i?l???r??q?u?'?i?l????m?'?a??n?i?v??d?o?n?n????,P?l?e??1?i?d???e???p?o?u?r??q?u?'?i?l?a?t?t?e?n?t?i?o?n??m?'?a??a??s?o??v?o?u?l?u?u????m?i?s?e???t?r?a?v?a?i?l?m?'?o?p?o?u?r???a?c?c?e?p?t??n?r?a?p?p?o?r?t?e?u?r??t?d?e?b?l?e??d?ee?a??t?h???s?e.u?t?i?e?n????e?x?p?r?i?m?e?r?c?m?a??oM?a?d?a?m?e?u?p??l??o?c?c?a?s?i?o?n??a?t?r?a?v?a?i?l?i?d????O?r?s?a?y,?p?o?u?r?H?m?e?n?e?r????????d?e???b?i?e?n??c?h?a?r?g???c?e?r?e?c?h?e?r?c?h?t?r?a?v?a?i?l.?a?u?J?e?p?o?u?r??l?f?a?i?t??e?n???r?e?m?e?r?c?i?e??i?n?f?i?n?i?m?e?n?t.?eJ?eu?t?i?e?n??r?????l?e???e?x?p?r?i?m?e?r??d?e?t?o?u?t?e?t?h???s?e.?m?a??e?x?p?r?i?m?e?r??r?e?c?o?n?n?a?m?a??i?s?s?a?n?c?e???????d?a?n??M?o?n??g?r?a?n?d?e??s?i?e?u?r?,A?u??r?o?f?e??-?p?a?r?t?i?c?i?p?????J?n?i?v?yL?c?e?t?t?e1,?d?'?e?f?f?e?c?t?u?e?r??a?v?o?i?r?,?d?eS?t?r?a??-?p?a?r?t?i??d?'?u?n?ed?e?p?o?u?r??j?u?r?yL?t?h???s?e.?y?o?n1,?t?i?e?n???c?o-?e?n?c?a?d?r?a?n?t????d?eM?o?n?s?i?e?u?r??c?e?t?t?e?e?t?c?o?l?l?a?b?o?p?a?r?t?l?U?b?o?u?r?g,?n?i?v??p?a?r?te?r?s?i?t???a?v?o?i?r?R?e?m?e?r?c?i?e?m?e?n?t???a?u?,?u?r?P?d?e?r??t?h???s?eo?f?e?s?s?e?u?r??d?'?a?u?t?r?e???
tel-00561660, version 1 - 1 Feb 2011TetraNUC
Jerzy DUDEK
Jacques MEYER
Michelle MEYER
l’IPNLyon
?l??a?n?a?l?y?s?e?d?e???d?o?n?n???e??.?d?e??c?eM?e?r?c?i??l?o?r???p?o?u?r???l?e???e???s?u?g?g?e?s?t?i?o?n??,?n??l?e???e?t?r?e?J?en?q?u?i??s?e?i?g?n?e?m?e?n?t???t?r?????q?u?'?i?l?c?e???m?'?a?!?d?o?n?n????????p?o?u?r?d?a?m?e?m?e?n?e?r??d????????m?o?n??b?i?e?n??e?n?f?i?n??c?e?t?t?e??a?n?a?l?y?s?e.?nC?e???d?r?e?e?t?m?e?r?c?i?e?m?e?n?t???d?o?n?n??????'?a?d?r?e?s?s?e?n?tt?r?o?i?????g?a?l?e?m?e?n?tB?o?n?n?e???!?l?a??r?e?m?e?r?c?i?e?m?e?n?t?c?o?l?l?a?b?o?r?a?t?i?o?n??m?e???s?u?r??e?t?t?r?a?v?a?i?l?l?e?r??m?'?a?v?o?i?r??p?o?u?r??m?'?a?v?o?i?r?,?e?e?n??j?o?u?r???p?a?r?-?e?n??t?i?c?u?l?i?e?r??M?o?n??l?e??s?i?e?u?r??d?e??S?t?r?a?s?b?o?u?r?g?d?e????f?a?i?t,?s?o?r?t?eP?s?e?r?o?f?e?s?s?e?u?r??d???c?o?n?d?i?t?i?o?n??.??l?l?U?e?n?c?o?u?r?a?g?e?m?e?n?t???n?i?v??p?e?n?d?a?n?te?r?s?i?t???S?t?r?a?s?b?o?u?r?g?a?n?n???e??1?t?h???s?e.,?c?o?n?t?i?n?u?a?t?i?o?n??p?o?u?r?!?l?e??U?c?o?u?r???g?r?a?n?d??s???j?o?u?r????'?a?d?r?e?s?s?e,M?o?n?s?i?e?u?r??r?o?f?e?s?s?e?u?r???q?u?e?l?U,e?r?s?i?t??M?a??y?o?n1,?a?c?c?u?e?i?l?l?i??l?e?u?r??s?u?r??l?a?P?s?y?m???t?r?i?e????t???t?r?a???d?r?i?q?u?e?n?i?v??e?tL?p?o?u?r??p?o?u?r??a?v?o?i?r??a?i?d?e?l?u??p?o?u?r??e?t?e?n?c?o?u?r?a?g???c?o?r?r?i?g???l?l?e??c?p?r?e?m?i?e?r???h?a??d?ep?i?t?r?e?s???j?o?u?r??t?h???o?r?i?q?u?eF?r?a?n?c?e.?d?e?s?o?u?h?a?i?t?e?r?a?i??c?e?r?e?m?e?r?c?i?e?r??t??t?o?u??t?e?m?e?m?b?r?e?t?h???s?e.?J?e?d?i?f?f???r?e?n?t??v?o?u?d?r?a?i???s?e?r?v?i?c?e???p?o?u?r????g?a?l?e?m?e?n?t?r?e?m?e?o?n?t?r?c?i?e?r??e?l??e?n?s?e?m?b?l?e??d?u??q?u?e?g?r?o?u?p?e?t?r?a?v?a?i?lM?a?t?i???r?e?d???r?o?u?l?eN?u?c?l???a?i?r?e?a?n???p?o?u?r??e?l?e???b?o?n?n?e???a?i?d?e??
tel-00561660, version 1 - 1 Feb 2011Resume
Des calculs theoriques utilisant la methode de champ moyen ont suggere l’existence
des formes du noyau avec la symetrie tetraedrique et/ou octraedrique dans la region
156 160des terres rares au voisinage des noyaux Gd et Yb. Dans les noyaux avec une
symetrie tetraedrique pure, des transitions intra-bande E2 a bas spin dans des bandes
de parite negative disparaissent ou sont tres faibles. Ce travail est dedie a une re-
156cherche experimentale de la symetrie tetraedrique dans le noyau Gd. Une experience
a ete faite a Jyv askyl a avec le multi-detecteur JUROGAM, sur la reaction de fusion -
154 156evaporation Sm(, 2n) Gd. L’analyse des donnees, a etabli les rapports d’embran-
chement de deux bandes de parite negative et a permis, par distribution angulaire, de
conna^ tre la nature d’une nouvelle transition. Les rapports d’embranchement obtenus
sont comparables avec ceux des experiences precedentes et quelques limites superieures
ont ete determinees. L’absence de transitions a bas spin (I < 9 ) dans la bande de
parite negative a spin impair a ete con rmee. Ces resultats ont renforce l’hypothese
156d’une symetrie tetraedrique dans le noyau Gd.
La spectroscopie est l’outil majeure utilise dans ce travail. Les principes ainsi
qu’une etude de simulation realiste sont detailles dans ce manuscrit. La simulation
avec des evenements realistes a ete faite pour comparer la fonction de reponse de
deux types de multidetecteurs EUROBALL et AGATA. Les resultats montrent que
sous certain conditions la phase demonstrateur d’AGATA peut ^etre utilisee pour la
recherche d’evenements rares.
tel-00561660, version 1 - 1 Feb 2011tel-00561660, version 1 - 1 Feb 2011Abstract
Theoretical calculations using realistic mean- eld method suggest the existence of
nuclear shapes with tetrahedral and/or octahedral symmetries in some rare earth nuclei
156 160around Gd and Yb. In nuclei with exact tetrahedral symmetry, the E2 intra-band
transitions are predicted to vanish completely or to be very weak. This work is devoted
156to an experimental research of the tetrahedral symmetry in the nucleus Gd. An
experiment has been carried out with the JUROGAM - rays detector at Jyv askyl a by
154 156using the fusion - evaporation reaction Sm(, 2n) Gd. In analysis, the branching
ratios of two parity negative bands were determined, the angular distribution has been
analyzed to determine the nature of one inter-band transition between these two bands.
The transitions strength ratios determined are of the same order of magnitude as
previous experiments, and some upper limits have been established for the lowest spin.
The missing of the E2 transitions below the I = 9 states in the odd spin parity
negative band were con rmed. The results of this work reinforced the hypothesis of the
156tetrahedral symmetry in the nucleus Gd.
-ray spectroscopy is the major tool used for this work. Detection principles and-
ray simulations are detailed in the document. The simulation, based on realistic events,
has been realised to compare the response function of two multidetectors EUROBALL
and AGATA. The results show that under certain conditions the rst phase of AGATA
(demonstrator) is also a tool to search for rare events.
tel-00561660, version 1 - 1 Feb 2011tel-00561660, version 1 - 1 Feb 2011Table des matieres
Introduction 9
I Elements theoriques et symetrie tetraedrique 13
I.1 Les modeles du noyau 14
I-1.1 Modele de la goutte liquide . . . . . . . . . . . . . . . . . . . . . . 14
I-1.2 Parametrisation de la surface nucleaire . . . . . . . . . . . . . . . 15
I-1.3 Model