12C(n,n + 3α) and 12C(n,α0)9Be cross sections in the MeV neutron energy region

Cross sections of the 12C(n, n+3α) reaction are of great significance in understanding the nuclear reaction mechanism and in the applications of nuclear technology. However, large differences (≈ 200%) exist in the 12C(n, n+3α) cross section data of measurements and evaluations. Using a single crystal chemical vapor deposited (sCVD) diamond detector as an active target, cross sections of the 12C(n, n+3α) and 12C(n, α0)9Be reactions were measured simultaneously in the neutron energy region of 9.50 – 14.67 MeV. The present cross sections of the 12C(n,α0)9Be reaction are consistent with the results of the latest measurement, which confirms the reliability of this work. The measurement results of the 12C(n, n+3α) reaction with uncertainties smaller than 15% contribute to effectively clarify the discrepancies of the measurements and evaluations. To our knowledge, this is the first time to measure the 12C(n, n+3α) cross sections using the diamond detector as an active target. Our method can be used in the future measurements to constrain the 12C(n, n+3α) excitation function in a much wider neutron energy region. R-matrix analysis was carried out for n+12C system using the RAC code in the neutron energy region below 30 MeV. Systematic and reliable calculation results are obtained for various reaction channels.