Alpha structure of12B studied by elastic scattering of8Li EXCYT beam on4He thick target

The 8Li elastic scattering on 4He in inverse kinematics has been studied in order to search for 8Li-α cluster configurations in excited states of 12B. The experimental technique, the inverse kinematic thick target method (TTIK), involved a 8Li beam provided by the EXCYT facility at an initial energy of Eb=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 ΔE-E silicon detector telescopes. The explored 8Li-α centre-of-mass energy ranges from ECM=2.7 MeV up to ECM=9.6 MeV. A micro-channel plate, placed before the gas chamber, is used to measure the time interval between the entrance of the 8Li 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.