A. C. C. Villari

The 12C+24Mg elastic scattering: An example of anomalous transparency at coulomb barrier energies

Abstract Fifteen complete angular distributions of the elastic scattering of 12 C+ 24 Mg were measured at energies around the Coulomb barrier ( E cm = 10.67–16 MeV). The angular distributions are strongly oscillating and could be well described by an optical potential family, whose real part was determined without continuous ambiguity. The imaginary part of this optical potential is very shallow. At four energies the inelastic scattering angular distributions leading to the 2 + state of the 24 Mg were also measured and analysed with coupled-channels calculations. The volume integrals of the optical potentials used in the coupled-channels calculations present the threshold anomaly in their energy dependence, with a clear Q -value dependence.

The optical theorem and forward glory effects in heavy-ion scattering

Abstract A detailed discussion of the optical theorem for heavy-ion scattering is given. It is pointed out that a careful application of this theorem to light heavy-ion systems may yield information about the nuclear interaction at distances corresponding to forward glory trajectories. Applications to several cases are presented.

Back-angle anomaly and coupling between seven reaction channels of 12C + 24Mg using algebraic scattering theory

Abstract We measured six fairly complete angular distributions of elastic, inelastic and α-transfer reactions of the 12 C + 24 Mg system at E CM =25.2 MeV. We performed coupled channels calculations using algebraic scattering theory with the nuclear algebraic potential derived from nuclear phase shifts and using the available structure information for the inelastic coupling strengths. The back angle rise in the elastic cross section is fully explained by the couplings between elastic and transfer channels.

Production of superheavy elements at GANIL

A long-term new experimental program has begun at GANIL, i.e. search for new super heavy nuclei and their structure. The first part consists in studying the structure of the 273110 isotope which involves the development of high intensity Se beam. In parallel, reactions involving Inverse Kinematics will be studied allowing to have a versatileness set-up. By adding germanium and electron detectors, spectroscopic studies could be made on trans-fermium elements. Preliminary results showed that the Wien Filter has a suppression of the incident beam with a 1010 factor, which is comparable with results elsewhere. We show recent results with the present set-up at GANIL in producing Fr isotopes in the Kr+Sb reaction. We present also the result of our Kr+Pb experiment, which tried to reproduce the Berkeley result of the element 118.

Anomalous heavy ion scattering near the Coulomb barrier

Abstract Striking oscillations were found in the elastic scattering of 12 C + 24 Mg near the Coulomb barrier. These oscillations are not reproduced by the standard potentials at higher energies and provide the determination of the optical potential without continuous ambiguity. The dispersion relation between the real and imaginary parts of this optical potential is not satisfied at the strong absorption radius, but holds for their volume integrals.

Combined target-ion source unit for production of rare nuclides

A combined target-ion source unit (ionizing target) has been developed for the on-line production of radioactive single-charged ions. The target is able to withstand temperatures of up to 2500 °C and also acts as an ion source of surface, electron-beam, and laser ionizations. Using tantalum foil as a target material, the on-line combined target-ion source unit efficiency, which is the product of the ionization and release efficiencies, has been obtained for neutron-deficient isotopes of Eu, Gd, and Yb. These nuclides were ionized by the surface ionization inside a hot tungsten target container, holding tantalum foils as a target material. The results of the combined target-ion source unit use for on-line laser resonant ionization spectroscopy investigation of neutron-deficient Gd isotopes have been also presented. For neutron-rich isotopes produced from a high-density UC target, which were ionized by the surface ionization inside the target container, the ionization efficiency values have been obtained close to 100% for Rb and Cs and 10% for In. For Ag and Sn neutron-richisotopes, the values of the electron-beam ionization efficiency in the volume of the targetcontainer, correspondingly equal to 4% and 2%, have been obtained.

Total reaction cross section and forward glory for 12C + 16O

Abstract A method based on the generalized optical theorem is proposed for the determination of the total reaction cross section from elastic angular distributions. This method was applied to 16 complete elastic angular distributions of the 12 C + 16 O at energies between E c.m =8.55 MeV and E c.m = 26.74 MeV. Some of the angular distributions were measured at the Sao Paulo Pelletron Laboratory. Angular distributions measured by the Erlangen and Saclay groups were also used. The reaction cross section is compared with fusion measurements and with σ R obtained by indirect methods. The existence and conditions for the observation of the nuclear forward glory scattering are investigated.

Orbiting in the algebraic scattering framework

Abstract Experimental results on orbiting phenomena in 18 O+ 10,11 B systems at E c.m. =18.8 and 19.9 MeV are presented. We show that all features of the orbiting phenomena of 11 B( 18 O, 18 O) 11 B and related transfer reactions are explained by a complete coupled-channels calculation in the AST framework. It is also shown that the orbiting features and the back-angle anomaly are strongly related and explained by the same channel coupling.

Total efficiency of an isotope-separator-on-line production system based on an electron cyclotron resonance ion source associated with a carbon target: The case of SPIRAL 1

An original approach to the time behavior of an isotope-separator-on-line production system is proposed in the case of a production system where the target and the ion source are connected through a conductance much larger than that of the exit hole of the source. One major goal of this article is to derive the analytical expression of the response time of the system for noble gases from statistical parameters only, which can be deduced from a few simple measurements. The validity limits of the expression of the total efficiency are given, and the calculations are compared to the results obtained at GANIL during operation of SPIRAL 1, using a carbon target close coupled to a multicharged electron cyclotron resonance ion source. The final analytical expression for the total efficiency shows that the usual product of diffusion efficiency, effusion efficiency, and ionization efficiency cannot be applied in our case. We show how it is possible to predict the atom-to-ion transformation efficiency for radioactive isotopes of noble gas using response times measured for stable isotopes.

Radioactive ion beam production at GANIL: Status and prospectives

Production of radioactive ions has started at GANIL on the SPIRAL facility since 2001 and numerous multicharged radioactive ion beams have been delivered for high energy nuclear experiments. This article makes an overview of the different beams that have been produced. In the mean time, an important R and D research program is continued in oder to produce new species of radioactive elements. A new concept of multicharged radioactive production that couples a monocharged ion source, based on the monolithe concept, to an ecr ion source like nanogan3 is under developments and is described The development of monocharged ion sources with high efficiencies is also motivated by a new big project that is under studies at GANIL : the SPIRAL 2 Project. The goal of this project consists in extending the disponible radioactive ion beams to very heavy elements created with a new method of production : while the spiral 1 facility uses the projectile fragmentation for radioactive nuclei production, the spiral 2 project is based on the fission of a Uranium carbide target induced by a neutron flow created by a high intensity deuton beam. The principle and an overview of the project is presented.Production of radioactive ions has started at GANIL on the SPIRAL facility since 2001 and numerous multicharged radioactive ion beams have been delivered for high energy nuclear experiments. This article makes an overview of the different beams that have been produced. In the mean time, an important R and D research program is continued in oder to produce new species of radioactive elements. A new concept of multicharged radioactive production that couples a monocharged ion source, based on the monolithe concept, to an ecr ion source like nanogan3 is under developments and is described The development of monocharged ion sources with high efficiencies is also motivated by a new big project that is under studies at GANIL : the SPIRAL 2 Project. The goal of this project consists in extending the disponible radioactive ion beams to very heavy elements created with a new method of production : while the spiral 1 facility uses the projectile fragmentation for radioactive nuclei production, the spiral 2 project ...