Alpha structure of 12B studied by elastic scattering of 8Li EXCYT beam on 4He thick target

The (8)Li elastic scattering on (4)He in inverse kinematics has been studied in order to search for (8)Li-alpha cluster configurations in excited states of (12)B. The experimental technique, the inverse kinematic thick target method (TTIK), involved a (8)Li beam provided by the EXCYT facility at an initial energy of E(b)=30.6 MeV which is continuously degraded down to zero in the passage through a helium extended thick target. After the interaction, the recoil alpha particles were detected by using four Delta E-E silicon detector telescopes. The explored (8)Li-alpha centre-of-mass energy ranges from E(CM)=2.7 MeV up to E(CM)=9.6 MeV. A micro-channel plate, placed before the gas chamber, is used to measure the time interval between the entrance of the (8)Li into the chamber and the arrival of the recoil alpha particle on the detectors. This "time interval" measurement improves the TTIK technique allowing the discrimination of elastic from inelastic events. In this paper, the experimental technique will be described and the preliminary results for the elastic cross section will be shown.