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Öğe Conceptual design and infrastructure for the installation of the first AGATA sub-array at LNL(Elsevier Science, 2011) Gadea, Andrés; Farnea, Enrico; Valiente-Dobòn, Jose Javier; Million, Bénédicte; Mengoni, Daniele; Bazzacco, Dino B.; Recchia, Francesco; Sezgin, AydınThe first implementation of the AGATA spectrometer consisting of five triple germanium detector clusters has been installed at Laboratori Nazionali di Legnaro, INFN. This setup has two major goals, the first one is to validate the gamma-tracking concept and the second is to perform an experimental physics program using the stable beams delivered by the Tandem-PIAVE-ALPI accelerator complex. A large variety of physics topics will be addressed during this campaign, aiming to investigate both neutron and proton-rich nuclei. The setup has been designed to be coupled with the large-acceptance magnetic-spectrometer PRISMA. Therefore, the in-beam prompt gamma rays detected with AGATA will be measured in coincidence with the products of multinucleon-transfer and deep-inelastic reactions measured by PRISMA. Moreover, the setup is versatile enough to host ancillary detectors, including the heavy-ion detector DANTE, the gamma-ray detector array HELENA, the Cologne plunger for lifetime measurements and the Si-pad telescope TRACE. In this paper the design; characteristics and performance figures of the setup will be described.Öğe Crosstalk corrections for improved energy resolution with highly segmented HPGe-detectors(Elsevier Science Bv., 2009) Bruyneel, Bart; Reiter, Peter; Wiens, Andreas; Eberth, Juergen; Hess, Herbert; Pascovici, Gheorghe; Warr, Nigel; Aydın, Sezgin; Bazzacco, Dino; Recchia, FrancescoCrosstalk effects of 36-fold segmented, large volume AGATA HPGe detectors cause shifts in the gamma-ray energy measured by the inner core and outer segments as function of segment multiplicity. The positions of the segment sum energy peaks vary approximately linearly with increasing segment multiplicity. The resolution of these peaks deteriorates also linearly as a function of segment multiplicity. Based on single event treatment, two methods were developed in the AGATA Collaboration to correct for the crosstalk induced effects by employing a linear transformation. The matrix elements are deduced from coincidence measurements of gamma-rays of various energies as recorded with digital electronics. A very efficient way to determine the matrix elements is obtained by measuring the base line shifts of untriggered segments using gamma-ray detection events in which energy is deposited in a single segment. A second approach is based on measuring segment energy values for gamma-ray interaction events in which energy is deposited in only two segments. After performing crosstalk corrections, the investigated detector shows a good fit between the core energy and the segment sum energy at all multiplicities and an improved energy resolution of the segment sum energy peaks. The corrected core energy resolution equals the segment sum energy resolution which is superior at all folds compared to the individual uncorrected energy resolutions. This is achieved by combining the two independent energy measurements with the core contact on the one hand and the segment contacts on the other hand.Öğe High-spin level structure of 35 S(American Physical Society, 2014) Aydın, Sezgin; Ionescu-Bujor, M.; Recchia, Francesco; Lenzi, Silvia M.; Bouhelal, Mouna; Bazzacco, Dino B.; Bizzeti, P. G.; Bizzeti-Sona A.M.The nucleus 35S has been studied by in-beam ?-ray spectroscopy using the 24Mg(14N,3p) fusion-evaporation reaction at Elab=40 MeV. A level scheme extended up to J?=17/2+ at 8023 keV and J?=13/2- at 6352 keV has been established. Lifetimes of six excited states have been determined by applying the Doppler shift attenuation method. The experimental data have been compared with the results of large-scale shell model calculations performed using different effective interactions and model spaces allowing particle-hole excitations across the N=Z=20 shell gap. © 2014 American Physical Society.Öğe High-spin states and lifetimes in S-33 and shell-model interpretation in the sd-fp space(American Physical Society, 2017) Aydın, Sezgin; Ionescu-Bujor, M.; Gavrilov, G. Tz.; Dimitrov, B. I.; Lenzi, Silvia M.; Recchia, Francesco; Tonev, Dimitar; Bouhelal, Mouna; Kavillioglu, F.; Pavlov, P.; Bazzacco, D.; Bizzeti, P. G.; Bizzeti-Sona, A. M.; de Angelis, G.; Deloncle, I.; Farnea, E.; Gadea, A.; Gottardo, A.; Goutev, N.; Haas, F.; Huyuk, T.; Laftchiev, H.; Lunardi, S.; Marinov, Tz. K.; Mengoni, D.; Menegazzo, R.; Michelagnoli, C.; Napoli, D. R.; Petkov, P.; Sahin, E.; Singh, P. P.; Stefanova, E. A.; Ur, C. A.; Valiente-Dobon, J. J.; Yavahchova, M. S.The structure of the S-33 nucleus was investigated in the Mg-24(N-14, alpha p) fusion-evaporation reaction using a 40-MeV N-14 beam. The level scheme was extended up to an excitation energy of 11.7 MeV and spin 19/2+. Lifetimes of the intermediate-and high-spin states have been investigated by the Doppler shift attenuation method. Data were compared with different shell-model calculations where effective interactions involving two main shells, the sd and the fp, are used.Öğe High-spin structure and intruder excitations in Cl-36(American Physical Society, 2012) Aydın, Sezgin; Recchia, Francesco; Ionescu-Bujor, M.; Gadea, Andrés; Lenzi, Silvia M.; Lunardi, Santo; Ur, Calin Alexandru; Bazzacco, Dino B.; Bizzeti, P. G.; Bizzeti-Sona, A. M.; Bouhelal, M.; de Angelis, G.; Deloncle, I.; Farnea, E.; Gottardo, A.; Haas, F.; Huyuk, T.; Laftchiev, H.; Mengoni, D.; Menegazzo, R.; Michelagnoli, C.; Napoli, D. R.; Sahin, E.; Singh, P. P.; Tonev, D.; Valiente-Dobon, J. J.Excited states up to J(pi) = 11(-) at 10 296 keV and J(pi) = 10(+) at 10 707 keV have been populated in the odd-odd Cl-36 nucleus using the Mg-24(N-14,2p) fusion-evaporation reaction at E-lab = 31 MeV. Twenty new states and 62 new gamma transitions have been identified by employing gamma-gamma and gamma-gamma-gamma coincidences. Lifetimes have been investigated by the Doppler shift attenuation method. The experimental data have been compared with the results of large-scale shell-model calculations performed using different effective interactions and model spaces allowing particle-hole excitations across the N = Z = 20 shell gap.Öğe Level-scheme investigation of S-33(IOP PUBLISHING, 2014) Gavrilov, G. Tz.; Goutev, Nikolay; Dimitrov, B. I.; Tonev, Dimitar; Petkov, Pavel; de Angelis, Giacomo; Recchia, Francesco; Aydın, SezginAn angular correlation experiment was carried out for S-33 at Laboratori Nazionali di Legnaro with the gamma-ray detector array GASP. The reaction used was Mg-24(N-14,alpha p)S-33 at a beam energy of 40MeV. An analysis of DCO ratios and triple gamma coincidences was performed. So far, a new level depopulated by 3 gamma -ray transitions has been found and its spin was determined. The work for further extension of the level scheme is in progress.Öğe Lifetime measurements and the high-spin structure of Cl-36(IOP PUBLISHING, 2015) Aydın, Sezgin; Ionescu-Bujor, M.; Recchia, Francesco; Gadea, Andrés; Lenzi, Silvia; Lunardi, Santo; Ur, C?lin Alexandru; Bazzacco, DinoHigh-spin states in Cl-36 were populated through the Mg-24(N-14,2p)Cl-36 reaction at E(N-14)=31 MeV. Lifetimes have been determined for fifteen states by applying the Doppler shift attenuation method. The results indicated the onset of collectivity in the high spin negative parity states. Large basis shell model calculations have been performed to understand the underlying structure of these states.Öğe Neutron Skin Effects in Mirror Energy Differences: The Case of Mg-23-Na-23(American Physical Society, 2018) Boso, A.; Lenzi, Silvia M.; Recchia, Francesco; Bonnard, Jèrèmy; Zuker, Andrés P.; Aydın, Sezgin; Bentley, M. A.; Cederwall, BoEnergy differences between analogue states in the T = 1/2 Mg-23-Na-23 mirror nuclei have been measured along the rotational yrast bands. This allows us to search for effects arising from isospin-symmetrybreaking interactions (ISB) and/or shape changes. Data are interpreted in the shell model framework following the method successfully applied to nuclei in the f(7/2) shell. It is shown that the introduction of a schematic ISB interaction of the same type of that used in the f(7/2) shell is needed to reproduce the data. An alternative novel description, applied here for the first time, relies on the use of an effective interaction deduced from a realistic charge-dependent chiral nucleon-nucleon potential. This analysis provides two important results: (i) The mirror energy differences give direct insight into the nuclear skin; (ii) the skin changes along the rotational bands are strongly correlated with the difference between the neutron and proton occupations of the s(1/2) "halo" orbit.Öğe Spectroscopy of odd-mass cobalt isotopes toward the N = 40 subshell closure and shell-model description of spherical and deformed states(American Physical Society, 2012) Recchia, Francesco; Lenzi, Silvia M.; Lunardi, Santo; Farnea, Enrico; Gadea, Andrés; Mârginean, Nicolae Marius; Napoli, Daniel Ricardo; Aydın, SezginThe neutron-rich cobalt isotopes up to A=67 have been studied through multinucleon transfer reactions by bombarding a 238U target with a 460-MeV 70Zn beam. Unambiguous identification of prompt ? rays belonging to each nucleus has been achieved using coincidence relationships with the ions detected in a high-acceptance magnetic spectrometer. The new data are discussed in terms of the systematics of the cobalt isotopes and interpreted with large-scale shell-model calculations in the fpgd model space. In particular, very different shapes can be described in 67Co, at the edge of the island of inversion at N=40, where a low-lying highly deformed band coexists with a spherical structure.
