S. Tropea

Carbon fragmentation measurements and validation of the Geant4 nuclear reaction models for hadrontherapy

Nuclear fragmentation measurements are necessary when using heavy-ion beams in hadrontherapy to predict the effects of the ion nuclear interactions within the human body. Moreover, they are also fundamental to validate and improve the Monte Carlo codes for their use in planning tumor treatments. Nowadays, a very limited set of carbon fragmentation cross sections are being measured, and in particular, to our knowledge, no double-differential fragmentation cross sections at intermediate energies are available in the literature. In this work, we have measured the double-differential cross sections and the angular distributions of the secondary fragments produced in the (12)C fragmentation at 62 A MeV on a thin carbon target. The experimental data have been used to benchmark the prediction capability of the Geant4 Monte Carlo code at intermediate energies, where it was never tested before. In particular, we have compared the experimental data with the predictions of two Geant4 nuclear reaction models: the Binary Light Ions Cascade and the Quantum Molecular Dynamic. From the comparison, it has been observed that the Binary Light Ions Cascade approximates the angular distributions of the fragment production cross sections better than the Quantum Molecular Dynamic model. However, the discrepancies observed between the experimental data and the Monte Carlo simulations lead to the conclusion that the prediction capability of both models needs to be improved at intermediate energies.

Study of the rainbow-like pattern in the elastic scattering of 16O on 27Al at Elab. = 100 MeV

Recently, a rainbow pattern in the elastic scattering of 16O + 27Al at Elab. = 100 MeV was reported. In the present paper, we show that the predicted change of slope of the cross section, as a function of angle, is mostly due to the far-side component of the scattering, which is affected by the inelastic couplings. The experimental data is consistent with the calculations up to the inflection point, where the effect of the couplings is significant. New experimental data, in very good agreement with the theoretical expectations around the Coulomb rainbow angle, are also presented.

(18O,18Ne) double charge-exchange with MAGNEX

An experimental study concerning Double Gamow-Teller (DGT) modes in (18O,18Ne) Double Charge-Exchange reactions has been very recently performed at INFN-LNS laboratory in Catania. The experiment was performed using a 40Ca solid target and a 18O Cyclotron beam at 270 MeV incident energy. Charged ejectiles produced in the reaction were momentum analyzed and identified by MAGNEX spectrometer at very forward angles. Preliminary results are presented in the present paper.

The (18O, 16O) reaction as a probe for nuclear spectroscopy

The response of nuclei to the (18O, 16O) two-neutron transfer reaction at 84 MeV incident energy has been systematically studied at the Catania INFN-LNS laboratory. The experiments were performed using several solid targets from light (9Be, 11B, 12,13C, 16O, 28Si) to heavy ones (58,64Ni, 120Sn, 208Pb). The 16O ejectiles were detected at forward angles by the MAGNEX magnetic spectrometer. Exploiting the large momentum acceptance (−10%, +14%) and solid angle (50 msr) of the spectrometer, energy spectra were obtained with a relevant yield up to about 20 MeV excitation energy. The application of the powerful trajectory reconstruction technique did allow to get energy spectra with energy resolution of about 150 keV and angular distributions with angular resolution better than 0.3°. A common feature observed with light nuclei is the appearance of unknown resonant structures at high excitation energy. The strong population of these latter together with the measured width can reveal the excitation of a collective...

Two-neutron stripping in (18O, 16O) and (t,p) reactions

The 12C(18O,16O)14C reactions has been investigated at 84 MeV incident energy. The charged ejectiles produced in the reaction have been momentum analyzed and identified by the MAGNEX magnetic spectrometer. Q-value spectra have been extracted with an energy resolution of 160 keV (Full Width at Half Maximum) and several known bound and resonant states of 14C have been identified up to 15 MeV. In particular, excited states with dominant 2p - 4h configuration are the most populated. The absolute values of the cross sections have been extracted showing a striking similarity with those measured for the same transitions by (t,p) reactions. This indicates that the effect of the 16O core is negligible in the reaction mechanism.

The role of couplings in nuclear rainbow formation at energies far above the barrier

A study of the 16O+28Si elastic and inelastic scattering is presented in the framework of Coupled Channel theory. The Sao Paulo Potential is used in the angular distribution calculations and compared with the existing data at 75 MeV bombarding energy. A nuclear rainbow pattern is predicted and becomes more clear above 100 MeV.

Study of new resonances at high excitation energy by the 120Sn(p,t)118Sn reaction at 35 MeV

The 120Sn(p,t)118Sn reaction was investigated at 35 MeV incident energy. The 118Sn excitation energy spectrum was reconstructed up to about 16 MeV. Preliminary results show the presence of a broad resonance at high excitation energy, compatible with the predicted population of the Giant Pairing Vibration (GPV).

Transfer to the continuum of 14C via (18O, 16O) reaction

A study of the continuum of 14C populated by the 12C(18O, 16O)14C reaction at 84 MeV incident energy has been performed. The ejectiles have been momentum analyzed at forward angles by the MAGNEX magnetic spectrometer. The energy spectra were obtained up to about 20 MeV excitation energy. The scattering of two neutrons independently removed from the projectile as it passes the target nucleus has been described by means of an optical potential with a semi-classical approximation for the relative motion. The calculations describe a significant part of the continuum observed in the energy spectra. In particular, a resonance of the residual nucleus dominates the region near the two-neutron emission threshold.

Effects of the polarization potential on the classical elastic scattering trajectories of 16O + 27Al at 100 MeV

The 16O + 27Al elastic scattering is studied in the framework of Coupled Channel theory with Sao Paulo parameter free optical potential. The deflection function and the complex polarization potential are extracted. A surprising reduction of the overall absorption is found near the surface of the colliding systems. The semi-classical trajectories reveal a strong Ldependent behavior.

(18O,>16O) Two-neutron transfer reactions for spectroscopic studies

A systematic study of the response of different nuclei to the (18O,16O) two-neutron transfer reaction at 84 MeV incident energy was pursued at the INFN-LNS in Catania (Italy).The experiments were performed using several solid targets from light (9Be, 11B, 12,13C, 16O, 28Si) to heavier ones (58,64Ni, 120Sn, 208Pb). The 16O ejectiles were detected at forward angles by the MAGNEX magnetic spectrometer and identified without the need of time of flight measurements. Exploiting the large momentum (≈ 25%) and angular (50 msr) acceptance of the spectrometer, energy spectra were obtained with a relevant yield up to about 20 MeV excitation energy.A common feature of the light nuclei spectra is the strong population of states with well known configuration of two-particle over a core and the appearance of unknown resonant structures in the continuum. These latter can reveal the excitation of a collective mode connected with the transfer of a pair.For the heavier nuclei as 66Ni a completely different behaviour is obse...