TRIAC Progress Report - KEK

upstream of the pre-buncher, avoiding beam injection into the buncher during the
shaping time of the saw-tooth wave-form for beam bunching [3-15].
Fig. 3-10. Experimental set-up for the measurements of 12 C(α,γ) cross sections. Three NaI(Tl)
detectors are placed at 40 o , 90 o , 130 o relative to the beam direction. The scattering chamber was
installed at the center of the detectors and includes a water cooled target holder where several
12 C-enriched targets on the gold foil backing were set. The vacuum in the chamber was about 10 -7
Pa.
Fig. 3-11. Correlation in the energy and the time of γ-rays measured by the NaI(Tl) detector at 40 o
using bunched α-beams of 0.701 MeV/nucleon. Vertical and horizontal axes correspond to the
observed γ-ray energies in unit of MeV and the times-of-flight from the RF signals in unit of
nanosecond, respectively. Intensities of correlated events are presented by different colors as
indicated in the right-hand side of the figure. Events in the red circle indicate the characteristic γ
transitions from excited state populated by the reaction to the ground state in 16 O.
Using the beam-bunching system and experimental set-up shown in Fig. 3-10, the
experiment has been recently performed at four incident energies ((0.701, 0.774, 1.12
and 1.13 MeV/nucleon) of the α-beam. Figure 3-10 shows the experimental set-up,
which is similar to the one in Ref. 3-13 except for a water cooled target holder for the
63