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Several experiments around the world are looking for a new particle, named Dark Boson, which may do the link between the Ordinary Matter (which forms basically stars, planets, interstellar gas...) and the Hidden Sectors of the Universe. This particle, if it exists, would act as the messenger of a new fundamental interaction of nature. In this paper, the underlying Dark Sectors theory will be introduced first. A non-exhaustive summary of experimental studies carried out to date and foreseen in the incoming years will be presented after,including the 8Be anomaly. The last section will provide a status of the New JEDI**** project which aims to investigate the existence or not of a Dark Boson in the MeV range.

Radiative capture reactions on rare targets and prompt spectroscopy of neutron-rich nuclei produced in the neutron-capture induced-fission of 235U and 241Pu have been performed at the Institut Laue-Langevin (ILL). The high efficiency germanium (Ge) EXOGAM array has been used, complemented with Ge detectors from GASP and the ILL. LaBr3 detectors from the FATIMA collaboration have also been coupled to EXOGAM to measure lifetimes of lowlying excited states. The measured characteristics indicate very good performances of the overall setup. Some recent results will be discussed.

International audience; Nuclear fission is a complex process, still not yet well described by microscopic models, and its main observables are difficultto measure with accuracy. Following the capture of a thermal neutron the compound nucleus fissions in two fragments. Mostof the energy of the process is transferred in kinetic energy, whereas the nuclei are let in few tens of MeV excited states. Thisexcitation energy is then released, the majority of it within less than some nanoseconds, by the evaporation of a few neutronsand the emission of -rays in cascade.To overcome the low accuracy of microscopic models in the prediction of fission observables, nuclear technology relies onlibraries of evaluated data and semi-empirical models, like the GEF model for fission yield evaluations. Such a strategy requestssystematic and accurate experimental data on the few possible observables. Here we will present the advantages of studyingyields of fragment correlated pairs and their de-excitations using an array of high-resolution -ray detectors directly placedaround an actinide target irradiated by a thermal or cold neutron beam. Such a setup was installed at ILL in 2012 and 2013(EXILL) and campaigns were performed with 235U and 241Pu targets. This study is largely motivated by the future installation of apermanent -ray detector array at the ILL, which will be coupled to fission fragment detectors in a first construction phase and afragment separator in a second phase (FIPPS).An important outcome of EXILL data is the observation of the -ray cascade occurring in both fission fragments with an unambiguousdetermination of the fragments. The cascade is directly linked with the angular momentum of the fragments afterscission, which is one of the less precise and less understood properties. With the development of new simulation codes for theneutron evaporation and the -ray cascade like FIFRELIN or KEWPIE, systematic studies and comparisons with the large amountof experimental data resulting from double and triple gamma-ray coincidence analysis become possible. Preliminary results onthe gamma–ray cascades measured in the well produced Kr and Ba fragments and comparisons with FIFRELIN simulations willbe presented.

Nuclei around doubly-closed shells play a crucial role in studying both a) the couplings between valence nucleons which provide information on the effective nucleon-nucleon interaction and, b) couplings of the valence nucleons with core excitations, which may be used as a unique test of various effective interactions used in mean-field based models, like Skyrme, Gogny etc. From a broader perspective, understanding the coupling of a single particle to vibrational motion in nuclei is of primary importance, as this coupling is responsible for the quenching of spectroscopic factors [1]; it is also the key process at the origin of the damping of giant resonances [2]. The vibrational phonons are best known from the spectroscopic studies of doubly-magic nuclei in which they appear, in general, as the lowest excited states. For example, in 208Pb, the lowest excitation (at 2615 keV) is the 3– octupole vibration with a large E3 transition strength of 34 W.u. We investigated the low-spin structures of 210Bi and 206Tl up to their neutroncapture states at 4.6 and 6.5 MeV, respectively, by using 209Bi(n,)210Bi and 205Tl(n,)206Tl reactions induced by cold neutrons at ILL Grenoble. The 210Bi nucleus (one proton and one neutron above the 208Pb core) was populated in the experiment performed at the PF1B and cold-neutron facility in which - coincidences were measured with the EXILL array consisting of 16 Ge detectors. It is the first time when such large array was employed for 209Bi(n,)210Bi reactions studies so the decay scheme could be revised and significantly extended. The analysis of the angular correlations of  rays provided information about transitions multipolarities and helped with the spin-parity assignments. The structure arising from the excitations of valence proton and neutron was compared to the shell-model calculations. Some of the observed states must come from the coupling of the valence particles excitations with the first excited state in 208Pb, that is 3– octupole vibration. The 206Tl nucleus was populated in the first (commissioning) experiment of FIPPS facility at ILL Grenoble. The  rays from the capture state at 6.5 MeV were measured by the array of 8 Ge clovers. We want to present the preliminary results of the -coincidence analysis which will allow to significantly extend the experimental information on the energy levels in 206Tl. The 206Tl nucleus, having just one proton-hole and one neutron-hole with respect to the best known doubly magic core 208Pb, is an ideal system for testing old and developing new shell model interactions in the south-west quadrant of the nuclear chart with respect to 208Pb.

International audience; The coupling of very efficient gamma-ray arrays with large acceptance (or highly selective) spectrometers in the context of radioactive beams has pushed away the limits and opened up new possibilities in nuclear physics studies. At GANIL the EXOGAM array (a large efficiency gamma-ray array) has been coupled to VAMOS (a large acceptance spectrometer) and to SPEG (a highly selective spectrometer) to study many different aspects of nuclear structure and reactions covering the whole nuclear chart: indeed, this combination has been used to study neutron rich nuclei toward 54Ca, neutron deficient Sn isotopes around A=103, heavy elements around Md and No, reaction mechanism using the borromean light He isotopes, the nuclear structure in the island of inversion around 32Mg, and many other examples in various domain and energy regime. This is also the case for the very efficient large BaF2 array “Château de crystal” which is frequently coupled to SPEG to study nuclear structure far from stability. In this talk, the various possibilities offered at GANIL with such a coupling will be given. In the future, AGATA will be installed at GANIL to exploit the beams produced by the SPIRAL2 facility. The scientific objectives motivating this installation will be discussed. Again, it is anticipated that this new generation array will be coupled to spectrometers to better exploit the future beams

International audience; The mixing ratio of the main 320-keV, M1 + E2 ground-state γ transition in 210Bi has been more precisely quantified, allowing a significant reduction in the uncertainty of measurements of the neutron-capture cross section to the ground state of 210Bi from 25% to 0.9%. Accurate values for neutron-capture cross sections to both the ground and long-lived 9− isomeric state at 271 keV in 210Bi are of particular importance as Pb-Bi finds increased usage in Accelerator Driven Systems.

International audience; Gamma-ray spectroscopy is intensively used at GANIL to measure low lying states in exotic nuclei on the neutron-rich as well as on the neutron-deficient side of the nuclear chart. On the neutron deficient border, gamma-rays have been observed for the first time in 92Pd . The level scheme which could be established points to the role of isoscalar pairing. On the neutron rich side, the lifetime of excited states in nuclei around 68Ni have been been measured using the plunger technique. This allows us to study the evolution of collectivity in a broad range of nuclei. In 2014 GANIL will host the AGATA array for a campaign of at least 2 years. This array is based on the gamma-ray tracking technique, which allows an impressive gain in resolving power.

The combination of the intense cold neutron beam available at the PF1b beam position of the Institute Laue-Langevin (ILL) in Grenoble, together with the high detection efficiency of a large array of high purity Ge detectors (HPGe) has offered a unique opportunity for a set of experiments devoted to nuclear spectroscopy on stable isotopes as well as on exotic nuclei produced in the fission process of uranium and plutonium samples. The emitted γ-rays from neutron capture on stable targets as well as from the decay of fission fragments have been acquired in a trigger-less mode to preserve a maximum of information for further off-line treatment. A dedicated fully digital acquisition system using a combination of a 14-bit 100 MS/s digitisers with a PowerPC-based VME single board computer has been developed to ensure data collection and real-time processing capabilities. The present article will describe the experimental setup as well as the specific electronic configuration used during the EXILL campaign of measurements with particular emphasis on the technical achievements as well as on the preliminary results obtained in the various experiments.

The EXOGAM array is a high efficiency germanium-array installed at GANIL since 2001. It is heavily used to study the structure of exotic nuclei produced in heavy-ion induced reactions. Most of the time, the array is coupled to other ancillary detectors, and in particular to the VAMOS large acceptance spectrometer. Another key setup is the combination of EXOGAM, the Neutron Wall - a large array of liquid scintillator to measure neutrons - and DIAMANT, a light-charged particle CsI multidetector. In this talk some examples of studies of neutron-rich nuclei around 68Ni performed with VAMOS will be shown. This includes some lifetime measurements as well as the combined prompt and delayed gamma-ray spectroscopy of nuclei produced in deep-inelastic reactions. The coupling of EXOGAM with the Neutron wall and DIAMANT is designed to study neutron deficient nuclei. This has been done in the region below 100Sn, for N~Z nuclei located close to the proton line. The results obtained for the self-conjugate N=Z=46, 92Pd seem to underline the role of the isoscalar T=0 neutron-proton pairing in the profound modification of the low-lying level scheme. As a by-product, a full characterization of EXOGAM as a Compton polarimeter has been performed and the structure of 91Ru has been studied in great details.

The coupling of very efficient gamma-ray arrays with large acceptance (or highly selective) spectrometers has pushed away the limits and opened up new possibilities in nuclear physics studies. This is the case at GANIL with the setting up of EXOGAM (a large efficiency gamma-ray array) coupled to VAMOS (a large acceptance spectrometer). In this talk, the various possibilities offered at GANIL with such a coupling will be given. Other examples using the combination of SPEG and the Chateau de Cristal will also be shown.

The ISOL type SPIRAL facility at GANIL has been commissioned recently and delivers radioactive beams (RIBs) for physics since a couple of years. Despite many difficulties arising from both the complexity to produce good beam quality and intensity as well as to setup the appropriate detection system, the first experiments with SPIRAL have demonstrated that nuclear dynamics studies (nuclear structure and low energy reaction mechanism) at the Coulomb barrier are possible with that kind of beams. RIBs like $^{76}$Kr and $^{6,8}$He have been used to produce exotic nuclei via fusion evaporation or to study reaction mechanisms at low energy. These two examples will be detailed in this talk.

Exogam; The SPIRAL facility started to deliver radioactive ion beams (RIB) in september 2001 and some experiments have been performed in particular using the EXOGAM array. These experiments will be briefly described and the first outputs will be shown. The in-beam performances of EXOGAM will also be discussed.

18th IEEE-NPSS Real Time Conference (RT) on Computing Applications in Nuclear and Plasma Sciences -- JUN 11-15, 2012 -- Berkeley, CA, WOS: 000325827700015, This work describes new electronics for the EX-OGAM2 (HP-Ge detector array) and NEDA (BC501A-based neutron detector array). A new digitizing card with high resolution has been designed for gamma-ray and neutron spectroscopy experiments. The higher bandwidth requirement of the NEDA signals, together with the necessity for accuracy, require a high sampling rate in order to preserve the shape for real-time Pulse Shape Analysis (PSA). The PSA is of paramount importance for the NEDA to discriminate between neutrons and gamma-ray signals. Both high resolution and high speed parameters are often difficult to achieve in a single electronic unit. These constraints, together with the need to build new digitizing electronics to improve performance and flexibility of signal analysis in nuclear physics experiments, led to the development a new FADC mezzanine card. In this work, the design and development are described, including the characterization procedure and the preliminary measurement results., Generalitat Valenciana, Spain [PROMETEO/2010/101]; Swedish Research Council; Scientific and Technological Research Council of Turkey (TUBITAK); INFN, Italy; Spanish MINECO [AIC-D-2011-0746, FPA2011-29854, FPA2012-33560], This work was supported by the Generalitat Valenciana, Spain, under Grant PROMETEO/2010/101, the Swedish Research Council, and the Scientific and Technological Research Council of Turkey (TUBITAK). Some authors were supported in part by INFN, Italy, and by the Spanish MINECO under Grants AIC-D-2011-0746, FPA2011-29854 and FPA2012-33560.

This work is directly related to the evolution of radioactive ion beam (RIB) for physical studies in two projects at GANIL (Grand Accélérateur National d’Ions Lourds) SPIRAL and SPIRAL2 (Système de Production d’Ions Radioactifs Accélérés en Ligne).The first part of this work focus on studies of a MR-ToF-MS (multi-reflexions time-of-flight mass spectrometer) PILGRIM (Piège à Ions Lourds du GANIL pour la Résolution des Isobares en Masse) designed for mass separation and mesurement of radioactive isobars. MR-ToF-MS devices are already use around the world achieving high precision mass measurements (mass uncertainty down to a few 1E-07). The studies on PILGRIM focus on: ion bunch shape, thermal dependencies, masse resolution and development of mass measurement methods using one and two references. The maximal resolution obtained with the setup is 140 000 and both methods used allow a mass precision below 1E-07.The second part of this thesis focus on an experiment using the new FEBIAD (Forced Electron Beam Induced Arc Discharge) ion source developed at GANIL for the SPIRAL1 upgrade. This experience is divided into two stages: detection of recoil ions by a silicon detector DSSSD (Double Sided Silicon Strip Detector) and the gammas from decay by the detector array EXOGAM in one hand, and the mesure of the isomeric ratio between ions in ground state and those in isomeric state which form the radioactive ion beam of 38K in an other hand. We present: calibration of the detectors, analysis of detectors spectra, then gamma spectrum after Doppler corrections effect and finally isomeric ratio measurement. During this experiment, the FEBIAD source produced a radioactive ion beam of ~1E-06 pps with an isomeric ratio of ~ 20%. Gamma spectra from EXOGAM didn't give a value on seeked E2 matrix element., Ce travail de thèse s’inscrit dans le cadre du développement des faisceaux d'ions radioactifs (RIB) pour la physique dans deux grands projets au GANIL (Grand Accélérateur National d’Ions Lourds) SPIRAL et SPIRAL2 (Système de Production d’Ions Radioactifs Accélérés en Ligne).La première partie de cette thèse se concentre sur l'étude d'un MR-ToF-MS (multi-reflexions time-of-flight mass spectrometer) ; PILGRIM (Piège à Ions Lourds du GANIL pour la Résolution des Isobares en Masse) conçu pour la séparation et la mesure des isobares radioactifs en masse. Les MR-ToF-MS sont déjà utilisés dans le monde entier pour réaliser des mesures de masse de haute précision avec des incertitudes inférieures à quelques 1E-07. Les études de PILGRIM se concentrent sur : la forme des paquets d'ions, la dépendance des temps de vol en fonction de la température, la résolution de masse et la mise en place de méthodes de mesure de masse utilisant une ou deux références. La résolution maximal obtenue avec l'appareil est de 140 000 et les méthodes de mesures développée permettent une précision sur la mesure de masse inférieure à 10^-7.La deuxième partie de cette thèse se concentre sur une expérience utilisant la nouvelle source FEBIAD (Forced Electron Beam Induced Arc Discharge) développée au GANIL dans le cadre de l'amélioration de SPIRAL1. L'expérience se divisaient en deux étapes : la détection des produits de réaction par un détecteur silicium DSSSD (Double Sided Silicon Strip Detector) et les gammas de désexcitation par l'ensemble de détecteurs EXOGAM d'une part et la mesure du rapport isomérique entre les ions dans l'état fondamental et ceux dans l'état isomérique qui constituent le faisceau d'ion radioactif de 38K d'autre part. Nous présentons ici : l'étalonnage des détecteurs de l'expérience, l'analyse des spectres des détecteurs en germanium d'EXOGAM et du détecteur en silicium DSSSD, puis le spectre gamma obtenu après correction de l'effet Doppler et enfin la mesure du rapport isomérique. Lors de cette expérience, la source FEBIAD à produit un faisceau d'ions radioactifs d'environ 1E06 pps avec un rapport isométrique d'environ 20%. Les spectres d'EXOGAM n'ont cependant pas permis ici d'en déduire les valeurs des éléments de matrice recherchés.

Within the scope of atomic nuclear structure studies with neutron-induced reactions, this work presents the results of a fission fragment study in the N=50-60 region, the development of a fission event tagger, and the production of the isomer Pt-195m. Each of the different sub-topics has its origin in the 2012/13 EXILL campaign, where nuclear structure studies were carried out with neutron-induced reactions, and explored with a γ-efficient detector array. In the first part of this thesis, the neutron-rich region around neutron number N=50-60 was investigated with neutron-induced fission reactions on the fissile targets U-235 and Pu-241. Gamma spectroscopy methods were applied for the identification of the respective fission fragments, the assignment of γ transitions, and the analysis of lifetimes of excited states. The slope fit method as well as the recently developed generalized centroid difference method were used for the analysis of lifetimes in the low picoseconds to sub-nanoseconds range. Lifetimes for the nuclei Kr-92, Kr-93 and Zr-101 are presented. In the second part, first results of the development of a new detector for the discrimination of fission fragments are presented. This fission event tagger is intended to be used at the FIssion Product Prompt γ-ray Spectrometer (FIPPS) at the Institut Laue-Langevin. Within the scope of this study, two different detector designs, based on a solid plastic scintillator and an organic liquid scintillator, respectively, were tested. In the third part the possibility of the specific population of the spin-isomer in Pt-195 is discussed with special regard to its use as radioisotope in nuclear medicine. Such a specific activation could be realized via certain “doorway states” in photo-excitation reactions. The search for these doorway states was initiated within a neutron capture experiment at EXILL where potential states were found. The activation of the isomer via these states was tested afterwards with photonuclear reactions using the high intense γ-beam HIGS of the TUNL facility., Ce travail s'inscrit dans le cadre d'études de structures nucléaires réalisées en utilisant des réactions de fission induites par neutrons froids. Il décrit successivement les résultats d'une étude sur des noyaux ayant un nombre de neutrons N=50-60, sur le développement d'un marqueur d'événements de fission et enfin sur la production de l'isomère Pt-195m. Chacun des différents sous-thèmes trouve son origine dans la campagne EXILL qui s'est déroulée en 2012-2013 et durant laquelle un spectromètre de grande efficacité pour la détection des rayonnements γ (EXOGAM) a été utilisé auprès du réacteur à haut flux de neutrons de l'Institut Laue-Langevin (ILL). Dans la première partie de cette thèse, les noyaux d'intérêt ont été produits par fission induites par des neutrons sur les cibles fissiles U-235 et Pu-241. Des méthodes de spectroscopie γ ont été appliquées pour l'identification des fragments de fission, l'attribution des transitions γ à un noyau et l'analyse des durées de vie moyenne des états excités. L'analyse des durées de vie moyenne des états excités dans la plage de quelques picosecondes à quelques nanosecondes a été réalisée en utilisant deux méthodes complémentaires. Dans les deux cas, il s'agit de réaliser un spectre en temps construit à partir de la coincidence entre une transition qui alimente le niveau mesuré et une transition qui le désexcite. Les durées de vie moyenne pour les noyaux Kr-92, Kr-93 et Zr-101 sont présentées. Dans la seconde partie, les premiers résultats du développement d'un nouveau détecteur pour la discrimination des fragments de fission sont présentés. Ce marqueur d'événements de fission est destiné à être utilisé sur le spectromètre FIssion Prompt Product γ-ray Spectrometer (FIPPS) de l'ILL. Dans le cadre de cette étude, deux conceptions de détecteurs différentes, basées sur un scintillateur en plastique solide et un scintillateur liquide organique, ont été testées. Dans la troisième partie, la possibilité de la population spécifique de l'isomère de spin dans Pt-195 est examinée au regard particulièrement de son utilisation en tant que radio-isotope en médecine nucléaire. Une telle activation spécifique pourrait être réalisée grâce à l'existence d'états excités dont la structure permettrait une population ciblée dans le cas de l'utilisation de réactions de photo-excitation. La recherche de tels états a été initiée lors d'une expérience de capture de neutrons à EXILL dans laquelle des états potentiels ont été identifiés. L'activation de l'isomère par ces états a ensuite été testée avec des réactions photonucléaires à l'aide du faisceau haute intensité disponible auprès de l'installation γ HIGS de TUNL (Triangle Universities Nuclear Laboratory, Duke, USA).

Expérience GANIL/VAMOS/EXOGAM; In this thesis we investigated the structure of nuclei around 68Ni as well as the production, separation and identification of proton-rich isotopes lying in the vicinity of the doubly-magic 100Sn nucleus. In the first part, we discuss the evolution of collectivity and the interplay between collective and single-particle degrees of freedom in nuclei around 68Ni. We measured lifetimes in Zn isotopes around N = 40 produced in 238U + 70Zn deep-inelastic collisions at GANIL. We used a plunger device and the recoil-distance Doppler-shift method. The nuclei of interest were identified by the VAMOS spectrometer and the γ-rays with the EXOGAM array. The reduced electromagnetic transitions probabilities were extracted from the lifetimes. Several transitions and lifetimes are reported for the first time. The experimental results are discussed in the framework of shell model calculations. In the second part, the partial conservation of seniority in the g9/2 shell and its influence on one-particle transfer is discussed. The third part presents the analysis of a test performed at RIKEN (Japan) to evaluate two settings of the BigRIPS separator for optimizing the production and selection of 100Sn. This study has been used to setup our subsequent experiment, dedicated to the measurement of the Gamow-Teller strength in the decay of 100Sn. Nuclei around 100Sn were produced by fragmentation of a 345 MeV/u 124Xe beam on a Be target. The production cross-sections of nuclei around 100Sn were measured. The search for new isotopes and new isomers in all identified nuclei is presented.; Nous avons étudié la structure des noyaux autour de 68Ni, ainsi que la production, séparation et identification des isotopes se trouvant dans le voisinage du noyau doublement magique 100Sn. Dans la première partie, est discutée l'évolution de la collectivité et l'interaction entre degrés de liberté particule indépendante et collectifs autour de 68Ni. Nous avons mesuré des temps de vie dans les noyaux de Zn autour de N=40, produits par réactions profondément inélastiques 238U+70Zn à GANIL, à l'aide d'un "plunger". Les noyaux d'intéérêt, étaient identifiés par le spectromètre VAMOS, les gamma par le détecteur EXOGAM. Des durées de vie, nous avons extrait les probabilités de transition réduites. De nouvelles transitions ainsi que des durées de vie sont mesurées pour la première fois. Les résultats sont discutés dans le cadre de calculs modèle en couches. Dans la deuxième partie, la conservation partielle de séniorité dans la couche g9/2 et son influence sur le transfert d'une particule est discuté. La troisième partie présente un test réalisé à RIKEN (Japon), visant à évaluer deux configurations du séparateur BigRIPS, afin d'optimiser la production et la sélection des noyaux de 100Sn. Cette étude a été utilisée par la suite pour notre expérience, consacrée à la mesure de la force Gamow-Teller dans la désintégration de 100Sn. Les noyaux autour de 100Sn ont été produits par fragmentation d'un faisceau de 124Xe à 345 MeV/u. La section efficace de production des noyaux autour de 100Sn a été mesurée. La recherche de nouveaux isotopes et de nouveaux isomères est présentée.