L. Acosta

Results of the ASY-EOS experiment at GSI : the symmetry energy at suprasaturation density

Directed and elliptic flows of neutrons and light charged particles were measured for the reaction 197Au+197Au at 400 MeV/nucleon incident energy within the ASY-EOS experimental campaign at the GSI laboratory. The detection system consisted of the Large Area Neutron Detector LAND, combined with parts of the CHIMERA multidetector, of the ALADIN Time-of-flight Wall, and of the Washington-University Microball detector. The latter three arrays were used for the event characterization and reaction-plane reconstruction. In addition, an array of triple telescopes, KRATTA, was used for complementary measurements of the isotopic composition and flows of light charged particles. From the comparison of the elliptic flow ratio of neutrons with respect to charged particles with UrQMD predictions, a value \gamma = 0.72 \pm 0.19 is obtained for the power-law coefficient describing the density dependence of the potential part in the parametrization of the symmetry energy. It represents a new and more stringent constraint for the regime of supra-saturation density and confirms, with a considerably smaller uncertainty, the moderately soft to linear density dependence deduced from the earlier FOPI-LAND data. The densities probed are shown to reach beyond twice saturation.

β-delayed three-proton decay ofAr31

The beta decay of 31Ar, produced by fragmentation of a 36Ar beam at 880 MeV/nucleon, was investigated. Identified ions of 31Ar were stopped in a gaseous time projection chamber with optical readout allowing to record decay events with emission of protons. In addition to \b{eta}-delayed emission of one and two protons we have clearly observed the beta-delayed three-proton branch. The branching ratio for this channel in 31Ar is found to be 0.07(2)%.

High multiplicity α-particle breakup measurements to study α-condensate states

An experiment was performed to investigate α-condensate states via high α-particle multiplicity breakup. The nucleus of interest was 28Si therefore to measure multiplicity 7 particle breakup events, a highly granular detector with a high solid angle coverage was required. For this purpose, the CHIMERA and FARCOS detectors at INFN LNS were employed. Particle identification was achieved through ΔE-E energy loss. The α-particle multiplicity was measured at three beam energies to investigate different excitation regimes in 28Si. At a beam energy where the energy is sufficient to provide the 7 α-particles with enough energy to be identified using the ΔE-E method, multiplicity 7 events can be seen. Given these high multiplicity events, the particles can be reconstructed to investigate the breakup of α-condensate states. Analysing the decay paths of these states can elucidate whether the state of interest corresponds to a non-cluster, clustered or condensed state.

Scattering process for the system 7Be + 58Ni at 23.2 MeV beam energy

We measured for the first time the scattering process of 7Be nuclei from a 58Ni target at 23.2 MeV beam energy. The experiment was performed at the Laboratori Nazionali di Legnaro (LNL, Italy), where the 7Be Radioactive Ion Beam was in-flight produced with the facility EXOTIC. Charged reaction products were detected by means of the detector array DINEX, arranged in a cylindrical configuration around the target to ensure a polar angle coverage in the ranges θcm = 40°-80° and 110°-150°. The scattering differential cross section was analyzed within the optical model formalism with the coupled-channel code FRESCO to extract the total reaction cross section. The result was compared with those obtained at lower beam energies in an earlier experiment performed at the University of Notre Dame (USA). At the present stage of our analysis, the two data sets were found to be not fully consistent each other.

Near‐barrier scattering of 6He and 11Be

Experiments on halo nuclei at energies around the Coulomb barrier can provide good quality data on elastic, inelastic, breakup and nucleon transfer reactions. This information turns out to be very important to understand the structure and dynamics of these exotic nuclei. In this work we present relevant results obtained from recent scattering experiments of 11Be and 6He on heavy targets at energies around the Coulomb barrier. Our data exhibit strong absorption effects in the elastic channel. The role played by transfer and breakup channels, and the coupling to the continuum, are studied using CDCC and DWBA calculations.

Measurement of 19Ne spectroscopic properties via a new method of inelastic scattering to study novae

The accuracy of the predictions of the γ flux produced by a classical nova during the first hours after the outburst is limited by the uncertainties on several reaction rates, including the 18F(p,α)15O one. Better constraints on this reaction rate can be obtained by determining the spectroscopic properties of the compound nucleus 19Ne. This was achieved in a new inelastic scattering method using a 19Ne radioactive beam (produced by the GANIL-SPIRAL 1 facility) impinging onto a proton target. The experiment was performed at the VAMOS spectrometer. In this article the performances (excitation energy range covered and excitation energy resolution) and limitations of the new technique are discussed. Excitation energy resolution of σ = 33 keV and low background were obtained with this inverse kinematics method, which will allow extracting the spectroscopic properties of 19Ne.

Reaction Dynamics for the Systems 7Be, 8B + 208Pb at Coulomb Barrier Energies

In this contribution we describe the first results obtained for the investigation of the elastic scattering process in the reactions induced by the Radioactive Ion Beams Be and B on a Pb target at Coulomb barrier energies. The experimental data were analyzed within the framework of the optical model in order to extract the total reaction cross section. The comparison with data available in literature for reactions induced on Pb by light ions in the mass range A = 6-8 shows that the loosely-bound B has the largest reactivity.

Probing the Symmetry Term of the Nuclear Equation of State at High Baryonic Densities

In the ASY-EOS experiment flows of neutrons and light charged particles were measured for 197Au+197Au collisions at 400 MeV/nucleon, in order to investigate the strength of the symmetry term of the nuclear equation of state at supra-saturation densities. By comparing the experimental data with the UrQMD transport model predictions, we have extracted a new constraint in agreement with the moderately soft to linear density dependence obtained in the former analysis on FOPI-LAND data, but reducing the associated uncertainty by a factor ~ 2.

Campaign of measurements to probe the good performance of the new array FARCOS for spectroscopy and correlations.

During the last four years, several measurements have been carried out where the capabilities of FARCOS array were tested. In some of this occasions, FARCOS was coupled to the 4π array CHIMERA, permanently placed at INFN-Laboratori Nazionali del Sud, Catania in order to be tested in real experimental measurements. At the present situation, the FARCOS demonstrator is formed by 4 telescopes out of the originally 20 that will constitute the final array. Here are presented some preliminary results obtained with the new array, probing its qualities and showing the effectiveness of FARCOS telescopes. The initial encouraging results support the construction of the complete array.

Probing the qualities of diamond detectors for neutron identification at radiotherapy facilities

One of the capabilities of diamond detectors is the measurement of neutron radiation, due to their carbon composition. In these work is described a campaign of measurements related with neutron irradiation using different sources: starting with a 252Cf standard neutron source, continuing with a well-known nuclear reaction at a low-energy tandem accelerator and finishing with neutron radiation produced in a hospital radiotherapy machine. The aim of all these measurements is to evaluate the qualities of diamond device to detect neutron irradiation, thus proving they are good candidates to be used as neutron dosimeters at hospital accelerators. Our preliminary results show that diamond detectors are a promising tool to be implemented in such a kind of facilities.