Measurements of the 12C(n, n+3α) reaction and possible enhancement via the α-cluster structure

The 12 C( n, n + 3 α ) reaction was measured using a single-crystal diamond detector as an active target based on a quasi-monoenergetic D-T neutron source. The cross sections and the energy differential cross sections of the emitted neutrons of the 12 C( n, n + 3 α ) reaction in the 12 – 20 MeV neutron energy region were obtained. The present measurement cross section data with uncertainties smaller than 10 % help to clarify the large deviations (∼ 200 %) among different measurements and evaluations. The measured energy differential cross section data provide essential constraints for improving nuclear reaction model calculations of the n + 12 C system. Besides, two peaks were observed in the 12 C( n, n + 3 α ) excitation function at incident neutron energies of 12.05 (0.05) MeV and 16.74 (0.15) MeV, respectively. Analysis of the measured energy differential cross sections of the emitted neutrons indicates tentative evidence that these two peaks result from the neutron inelastic scattering of 12 C to high excited states with α -cluster structures. The present results are helpful for the understanding of the reaction mechanisms of light nuclei.