G. Scalia

Li-α CLUSTER STATES IN 12B USING 8Li + 4He INVERSE KINEMATICS ELASTIC SCATTERING

The 8Li elastic scattering on a 4He gas target was studied by means of the Inverse Kinematic Thick Target scattering method (TTIK) in order to investigate cluster configurations in excited states of 12B. A 8Li beam, at Ec.m. = 10.2 MeV, was provided by the EXCYT radioactive beam facility at Catania. The beam, while passing through the helium thick target decreases its energy, thus exploring the 8Li-α center-of-mass energy range 2.7 MeV≤ECM ≤9.6 MeV. Four ΔE-E silicon detector telescopes were used to detect the recoiling alpha particles. The time interval between the 8Li passing through a micro-channel plate foil, placed at the entrance of the chamber, and the detection of the α particles by the ΔE detectors was also measured. The time measurement allows to disentangle elastic from reactions events, otherwise impossible from energy measurements. This can be considered as an improvement of the TTIK method. In this paper the used experimental technique and the obtained preliminary results will be presented.

The Inverse Kinematics Thick Target scattering method as a tool to study cluster states in exotic nuclei

The inverse kinematics thick target scattering method (TTIK) was used to measure the 8Li resonant elastic scattering on a 4He target in order to investigate 8Li-α cluster configurations in excited states of 12B. A 8Li beam at Ebeam = 30.6 MeV, provided by the radioactive beam facility EXCYT of LNS in Catania, while passing through a thick Helium target decreases continuously its energy. Thus, elastic scattering can be induced starting from the initial beam energy down to zero. Time of flight measurement between beam particles passing through a MCP detector and α-particles impinging on the ΔE stage of a Si telescope detector allows the discrimination of elastic scattering from nuclear reaction events, thus representing an improvement of the TTIK method. In this paper the used experimental technique and preliminary results will be described.

8Li+α resonant elastic scattering: a tool to study cluster states in 12B

The 8Li+4He elastic scattering excitation function was measured by using the inverse kinematic thick target method. The 8Li beam was provided by the LNS radioactive facility EXCYT at an energy of 30 MeV and it was delivered into a large scattering chamber filled with 4He gas. The detection system was made by three silicon telescopes and one MCP. This last detector was used to measure the number of incident particles as well as the time of flight allowing for the discrimination between elastic and inelastic scattering. The setup and the experimental technique will be described in details and the results, as well as the comparison of the data with an R-matrix calculation, will be shown and discussed.

Structure effects in collisions induced by halo and weakly bound nuclei around the coulomb barrier

In this contribution, results concerning different reaction channels for the collisions induced by the three Be isotopes, 9,10,11Be, on a 64Zn target at energies around the Coulomb barrier will be presented. The experiments with the radioactive 10,11Be beams were performed at REX-ISOLDE (CERN) whereas the experiment with the stable weakly bound 9Be beam was performed at LNS Catania. Elastic scattering angular distributions have been measured for the three systems 9,10,11Be + 64Zn at the same center of mass energy. The angular distributions were analyzed with optical potentials and reaction cross sections were obtained from optical model calculations, performed with the code PTOLEMY. For the 11Be + 64Zn reaction, the break-up angular distribution was also measured.

Elastic scattering and direct reactions of the 1n halo 11Be nucleus on 64Zn near the barrier

Elastic scattering and direct reactions have been studied for the collisions induced by the three Beryllium isotopes 9,10,11Be, on a medium mass 64Zn target at energies near the Coulomb barrier. The elastic-scattering angular distribution of the 11Be halo nucleus shows a deviation from the classical Fresnel type diffraction behavior in the Coulomb-nuclear interference peak angular region. The deduced total reaction cross-sections for the 11Be collision is more than a factor of two than the ones measured in the collisions induced by 9;10Be. Moreover, for 11Be a large contribution to the total reaction cross-section due to transfer and break-up processes has been observed.

Evidence of strong effects of the 11Be halo structure on reaction processes at energies around the Coulomb barrier

The collision induced by the three Beryllium isotopes, 9,10,11Be, on 64Zn target were investigated at Ec.m. ≈ 1.4 the Coulomb barrier. Elastic scattering angular distributions were measured for the 9,10Be collisions whereas, in the 11Be case the quasielastic scattering angular distribution was obtained. A strong damping of the quasielastic cross-section was observed in the 11Be case, especially in the angular range around the Coulomb-nuclear interference peak. In this latter case a large total-reaction cross-section is found, more than a factor of two larger than the ones extracted in the reactions induced by the non-halo Beryllium isotopes. A large contribution to the total-reaction cross-section in the 11Be case could be attributed to transfer and/or break-up events.

Studying 12Bvia 8Li‐αresonant scattering

The inverse kinematics thick target scattering method (TTIK) has been used to study the 8Li elastic scattering on 4He in order to investigate 8Li‐α cluster configurations in excited states of 12B. A 8Li beam, provided by the radioactive beam facility EXCYT, at Ebeam = 30.6 MeV, passing through helium thick target, continuosly decreases its energy inducing elastic scattering starting from the initial energy down to zero. Four ΔE‐E double stage silicon detector telescopes were used to detect the recoil α‐particles coming from the scattering. Event by event time measurement between beam particles passing through a MCP detector and α‐particles impinging on ΔE stage allows elastic from inelastic events discrimination, thus representing an improvement of the TTIK method. In this paper the used experimental technique and some preliminary results will be briefly described.

Studying [sup 12]B via [sup 8]Li-α resonant scattering

The inverse kinematics thick target scattering method (TTIK) has been used to study the 8Li elastic scattering on 4He in order to investigate 8Li‐α cluster configurations in excited states of 12B. A 8Li beam, provided by the radioactive beam facility EXCYT, at Ebeam = 30.6 MeV, passing through helium thick target, continuosly decreases its energy inducing elastic scattering starting from the initial energy down to zero. Four ΔE‐E double stage silicon detector telescopes were used to detect the recoil α‐particles coming from the scattering. Event by event time measurement between beam particles passing through a MCP detector and α‐particles impinging on ΔE stage allows elastic from inelastic events discrimination, thus representing an improvement of the TTIK method. In this paper the used experimental technique and some preliminary results will be briefly described.

Elastic scattering of Beryllium isotopes near the Coulomb barrier

In this contribution, results of experiments performed with the three Beryllium isotopes 9,10,11Be on a medium mass 64Zn target, at a center of mass energy of ≈1.4 the Coulomb barrier, will be discussed. Elastic scattering angular distributions have been measured for the 9,10Be reactions. In the 11Be case the quasielastic scattering angular distribution was obtained. In the halo nucleus case, the angular distribution exhibit a non‐Fresnel‐type pattern with a strong damping of the Coulomb‐nuclear interference peak. Moreover, it is found that the total reaction cross‐section for the halo nucleus induced collision is more than double the ones extracted in the collisions induced by the non‐halo Beryllium isotopes. A large contribution to the total‐reaction cross‐section in the 11Be case could be attributed to transfer and/or break‐up events.

Studying 12B via 8Li‐α resonant scattering

The inverse kinematics thick target scattering method (TTIK) has been used to study the 8Li elastic scattering on 4He in order to investigate 8Li‐α cluster configurations in excited states of 12B. A 8Li beam, provided by the radioactive beam facility EXCYT, at Ebeam = 30.6 MeV, passing through helium thick target, continuosly decreases its energy inducing elastic scattering starting from the initial energy down to zero. Four ΔE‐E double stage silicon detector telescopes were used to detect the recoil α‐particles coming from the scattering. Event by event time measurement between beam particles passing through a MCP detector and α‐particles impinging on ΔE stage allows elastic from inelastic events discrimination, thus representing an improvement of the TTIK method. In this paper the used experimental technique and some preliminary results will be briefly described.