Studies of the 2α and 3α channels of the ^(12)C+^(12)C reaction in the range of E_(c.m.)=8.9 MeV to 21 MeV using the active target Time Projection Chamber

The ^(12)C+^(12)C fusion reaction was studied in the range of E_(c.m.)=8.9 to 21 MeV using the active-target Time Projection Chamber.With full information on all tracks of the reaction products,cross sections of the^(12)C(^(12)C,^(8)Be)^(16)O_(g.s.)channel and the ^(12)C(^(12)C,3a)^(12)C channel could be measured down to the level of a few milibarns.The ^(12)C(^(12)C,^(8)Be)^(16)O_(g.s.)reaction channel was determined to be 10_(-8)^(+24) mb at E_(c.m.)=11.1 MeV,supporting the direct a transfer reaction mechanism.The ^(12)C(^(12)C,3α)^(12)C reaction channel was studied for the first time using an exclusive measurement.Our result does not confirm the anomaly behavior reported in the previous inclusive measurement by Kolata et al.[Phys.Rev.C 21,579(1980)].Our comparisons with statistical model calculations suggest that the 3 a channel is dominated by the fusion evaporation process at E_(c.m.)>19 MeV.The additional contribution of the 3 a channel increases the fusion reaction cross section by 10% at energies above 20 MeV.We also find that an additional reaction mechanism is needed to explain the measured cross section at E_(c.m.)<15 MeV at which point the statistical model prediction vanishes.