Preliminary results of lifetime measurements in neutron-rich 53Ti

To study the nuclear structure of neutron-rich titanium isotopes, a lifetime measurement was performed at the Grand Accélérateur National d'Ions Lourds (GANIL) facility in Caen, France. The nucleiwere produced in a multinucleon-transfer reaction by using a 6.76 MeV/u 238U beam. The Advanced Gamma Tracking Array (AGATA) was employed for the γ-ray detection and target-like recoils were identified event-by-event by the large-acceptance variable mode spectrometer (VAMOS++). Preliminary level lifetimes of the (5/2−) to 13/2− states of the yrast band in the neutron-rich nucleus 53Ti were measured for the first time employing the recoil distance Doppler-shift (RDDS) method and the compact plunger for deep inelastic reactions. The differential decay curve method (DDCM) was used to obtain the lifetimes from the RDDS data

Search for 22^{22}Na in novae supported by a novel method for measuring femtosecond nuclear lifetimes

Classical novae are thermonuclear explosions in stellar binary systems, and important sources of $^{26}$Al and $^{22}$Na. While gamma rays from the decay of the former radioisotope have been observed throughout the Galaxy, $^{22}$Na remains untraceable. The half-life of $^{22}$Na (2.6 yr) would allow the observation of its 1.275 MeV gamma-ray line from a cosmic source. However, the prediction of such an observation requires good knowledge of the nuclear reactions involved in the production and destruction of this nucleus. The $^{22}$Na($p,\gamma$)$^{23}$Mg reaction remains the only source of large uncertainty about the amount of $^{22}$Na ejected. Its rate is dominated by a single resonance on the short-lived state at 7785.0(7) keV in $^{23}$Mg. In the present work, a combined analysis of particle-particle correlations and velocity-difference profiles is proposed to measure femtosecond nuclear lifetimes. The application of this novel method to the study of the $^{23}$Mg states, combining magnetic and highly-segmented tracking gamma-ray spectrometers, places strong limits on the amount of $^{22}$Na produced in novae, explains its non-observation to date in gamma rays (flux < 2.5x$10^{-4}$ ph/(cm$^2$s)), and constrains its detectability with future space-borne observatories.Comment: 18 pages, 3 figures, 1 tabl

EURO-LABS: Europe’s Super Community of Subatomic Researchers

International audienceEuropean-Laboratories for Accelerator Based Sciences (EURO-LABS) is a four-year project funded in the Horizon Europe program of the European Commission for Research infrastructure services to support health research, accelerate green and digital transformation, and advance frontier knowledge

Fusion et réactions directes autour de la barrière Coulombienne avec le noyau riche en neutrons 8He

Les faisceaux d'ions radioactifs comme l'8He ouvrent de nouvelles perspectives pour étudier l'influence de nouveaux aspects structurels sur les mécanismes de réaction. Cette thèse présente les premières investigations sur les réactions induites par le noyau d'8He, faiblement lié et Borroméen, aux énergies autour de la barrière Coulombienne. La faible intensité des faisceaux d ions radioactifs (~10^5 pps) nécessite le développement de techniques sensibles et sélectives. Une méthode expérimentale été développée pour mesurer précisément les sections efficaces de fusion. Dans le système 8He+197Au, les fonctions d'excitation de fusion et de transfert de neutron(s) ont été mesurées autour de la barrière. Les sections efficaces différentielles et intégrales pour la diffusion élastique, le transfert de neutron(s) et la fusion ont également été obtenues dans le système 8He+65Cu à partir de mesures inclusives et exclusives des rayons gamma caractéristiques, des particules chargées et des neutrons. Ces résultats expérimentaux et les calculs en voies couplées illustrent l'interconnexion des différents processus. Cette étude permet de comprendre l'influence de la structure interne de l 8He sur l'effet tunnel et le transfert de neutron(s) et met en évidence un comportement inattendu au sein de la chaîne isotopique des Héliums. L'étude systématique des fonctions d'excitation de fusion montre que, contrairement aux attentes, l augmentation de la probabilité de l effet tunnel sous la barrière Coulombienne associée à la structure interne des noyaux est beaucoup plus importante pour les noyaux normaux que pour les noyaux légers exotiques faiblement liés.Radioactive ion beams like 8He, open new possibilities to investigate the influence of new and exotic structures on reaction mechanisms. This thesis presents the first investigations of reactions of the weakly bound, Borromean nucleus, 8He, at energies around the Coulomb barrier. The low intensity of radioactive ion beams (~10^5 pps) necessitated the development of a new sensitive and selective technique for the precise and accurate measurement of fusion cross sections. In the 8He+197Au system, excitation functions for fusion and neutron(s) transfer were measured. In the 8He+65Cu system, differential and integral cross sections for various processes like elastic scattering, neutron transfer and fusion were measured using both, inclusive and exclusive measurements of characteristic gamma-rays, charged particles and neutrons. These experimental results combined with coupled reaction channels calculations demonstrated the inter-connectivity among the various reaction processes. The internal structure of 8He influenced the tunneling process and neutron(s) transfer and interestingly, revealed an unexpected behavior within the Helium isotopic chain. Further, a systematic analysis of the known fusion excitation functions showed that the increase in sub-barrier fusion cross sections associated with the internal structure of nuclei, is in fact much larger for normal'' nuclei than for light, weakly-bound exotic'' nuclei.CAEN-BU Sciences et STAPS (141182103) / SudocSTRASBOURG-Bib.Central Recherche (674822133) / SudocSudocFranceF

Microscopes for the Physics at the Femtoscale: GANIL-SPIRAL2

International audienceLaboratory portrai

Formation Of Two-neutron Halo In Drip-line Nuclei from The Low-energy Neutron-neutron Interaction

International audienceThe formation of two-neutron halo is described using the neutron-neutron (n-n) interaction fixed at the low-energy n-n scattering limit. This method is tested for loosely-bound two neutrons in 24O, where a good agreement with experimental data is found. It is applied to halo neutrons in 22C in two ways: with the 20C core being closed or correlated due to excitations from the closed core. This nn interaction is shown to be strong enough to produce a two-neutron halo in both cases, locating 22C on the drip line, while 21C remains unbound. A unique relation between the two neutron separation energy, S2n, and the radius of neutron halo is presented. New predictions for S2n and the radius of neutron halo are given for 22C. The estimated halo radius is found to be consistent with a recent experimental data. The appearance of Efimov states is also discussed. Spectra of excited states in 22C are predicted. The n-n interaction used here is large compared to conventional shell-model interactions. Roles of three-body forces are discussed

« 50 ans de physique des deux infinis en Normandie » Le GANIL par Yvon Georget

International audienc

« 50 ans de physique des deux infinis en Normandie » Le GANIL par Yvon Georget

International audienc