Insights into Nuclear Clusters in 28^{28}Si via Resonant Radiative Capture Measurements

International audienceThe heavyion radiative capture reaction 12C(16O,$\gamma$)28Si has been studied at three energies on( ELab = 20.0 and 21.2 MeV) and off( ELab = 20.7 MeV) resonance at Triumf (Vancouver) using the stateoftheart Dragon 0° spectrometer and its very efficient associated BGO $\gamma$ array. Intermediate states around Ex = 11.5 MeV, carrying a large part of the resonant flux have been observed for the first time in this system. The nature of those doorway states is discussed in terms of recently calculated cluster bands in 28Si. The results are compared to a recent similar investigation of the 12C(12C,$\gamma$)24Mg reaction

12C nuclear reaction measurements for hadrontherapy

International audienceHadrontherapy treatments require a very high precision on the dose deposition ( 2.5% and 1-2mm) in order to keep the benefits of the precise ions' ballistic. The largest uncertainty on the physical dose deposition is due to ion fragmentation. Up to now, the simulation codes are not able to reproduce the fragmentation process with the required precision. To constraint the nuclear models and complete fragmentation cross sections databases; our collaboration has performed an experiment on May 2008 at GANIL with a 95 MeV/u 12C beam. We have measured the fluence, energy and angular distributions of charged fragments and neutrons coming from nuclear reactions of incident 12C on thick water-like PMMA targets. Preliminary comparisons between GEANT4 (G4BinaryLightIonReaction) simulations and experimental data show huge discrepancies

Decay of a Jπ=36+J^{\pi}=36^+ Resonance in the 24Mg+24Mg^{24}Mg + ^{24}Mg Reaction

The narrow ($\Gamma$=170 keV) and high spin ($J^{\pi}=36^+$) resonance in the $^{24}$Mg + $^{24}$Mg reaction at E$_{CM}$= 45.7 MeV has been associated with a hyperdeformed molecular state in $^{48}$Cr. Such a description has important consequences for the resonance decay into the favored inelastic channels. Through fragment- $\gamma$ coincidence measurements performed ON and OFF resonance using the PRISMA-CLARA array, we have identified the $^{24}$Mg states selectively populated: the $2^+$ and $4^+$ members of the ground state band

Transfer Reaction Studies with Spectrometers

International audienceThe revival of transfer reaction studies benefited from the construction of the new generation large solid angle spectrometers, coupled to large gamma arrays. The recent results of gamma-particle coincident measurements in Ca-40+Zr-96 and Ar-40+Pb-208 reactions demonstrate a strong interplay between single-particle and collective degrees of freedom that is pertinent to the reaction dynamics. The development of collectivity has been followed in odd Ar isotopes populated in the Ar-40+Pb-208 reaction through the excitation of the 11/2(-) states, understood as the coupling of single particle degrees of freedom to nuclear vibration quanta. Pair transfer modes is another important degree of freedom which is presently being studied with Prisma in inverse kinematics at energies far below the Coulomb barrier. First results from the Zr-96+Ca-40 reaction elucidate the role played by nucleon-nucleon correlation

A New Decay Path in the 12C+16O Radiative Capture Reaction

International audienceThe 12C(16O,$\gamma$)28Si radiative capture reaction has been studied at energies close to the Coulomb barrier at Triumf (Vancouver) using the Dragon spectrometer and its associated BGO array. It has been observed that the $\gamma$ decay flux proceeds mainly via states around 10–11 MeV and via the direct feeding of the 28Si 3 1-(6879 keV) and 4 2+(6888 keV) deformed states. A discussion is presented about this selective feeding as well as perspectives for the use of novel detection systems for the study of light heavy-ion radiative capture reaction

Molecular resonances and the Jacobi shape transition in 48^{48}Cr

The ^{24]Mg + $^{24}$Mg reaction has been studied at the Legnaro Tandem at a CM bombarding energy of 45.7 MeV where a narrow and high spin resonance has been reported previously. The decay of the resonance into the inelastic and fusion-evaporation channels has been investigated. The ON and OFF resonance decay yields have been measured using, for the inelastic channels, the fragment spectrometer PRISMA and the $\gamma$ array CLARA, and, for the fusion-evaporation channels, the Si array EUCLIDES and the $\gamma$ array GASP. The resonant effects observed in both experiments are discussed and it is suggested that the resonance populates a deformed $^{48}$Cr after a Jacobi shape transition

Nuclear reaction measurements of 95MeV/u 12C interactions on PMMA for hadrontherapy

Expérience GANILThe ion dose deposition in tissues is characterized by a favorable depth dose profile (i.e. Bragg peak) and a small lateral spread. In order to keep these benefits of ions in cancer treatments, a very high accuracy is required on the dose deposition (±3%). For given target stoechiometry and geometry, the largest uncertainty on the physical dose deposition is due to the ion nuclear fragmentation. We have performed an experiment at GANIL with a 95MeV/u 12C beam on thick tissue equivalent PMMA targets (thicknesses: 5, 10, 15, 20 and 25mm). The main goals of this experiment are to provide experimental fragmentation data for benchmarking the physical models used for treatment planning. Production rates, energy and angular distributions of charged fragments have been measured. The purpose of this paper is to present the results of this experiment

Fission yields of minor actinides at low energy through multi-nucleon transfer reactions of 238^{238}U on 12^{12}C

Expérience GANIL/VAMOSInternational audienceFirst preliminary results of fragments distribution as a function of theexcitation energy for different fissioning systems from U to Cm and 250Cfare presented. A new method based on inverse kinematics to study transferinducedfission of minor actinides was carried out in GANIL in 2008, andagain in 2011. In these experiments, a 238U beam at 6.1 AMeV impingedon a carbon target to produce fissioning systems by multi-nucleon transferreactions, resulting in the first experiments accessing the full identificationof a collection of fissioning systems and their corresponding fission fragmentsdistribution. The excitation energy is deduced from the detection ofthe recoil nucleus in an angular DE-E stripped silicon telescope, and theidentification of the fragments is made possible by the VAMOS spectrometer

Dependence of Fission-Fragment Properties On Excitation Energy For Neutron-Rich Actinides

Experimental access to full isotopic fragment distributions is very important to determine the features of the fission process. However, the isotopic identification of fission fragments has been, in the past, partial and scarce. A solution based on the use of inverse kinematics to study transfer-induced fission of exotic actinides was carried out at GANIL, resulting in the first experiment accessing the full identification of a collection of fissioning systems and their corresponding fission fragment distribution. In these experiments, a 238U beam at 6.14 AMeV impinged on a carbon target to produce fissioning systems from U to Am by transfer reactions, and Cf by fusion reactions. Isotopic fission yields of 250Cf, 244Cm, 240Pu, 239Np and 238U are presented in this work. With this information, the average number of neutrons as a function of the atomic number of the fragments is calculated, which reflects the impact of nuclear structure around Z=50, N=80 on the production of fission fragments. The characteristics of the Super Long, Standard I, Standard II, and Standard III fission channels were extracted from fits of the fragment yields for different ranges of excitation energy. The position and contribution of the fission channels as function of excitation energy are presented