Cross sections of the Ca40(n,α0)37Ar and Ca40(n,α)37Ar reactions in the 8.50–9.50 MeV neutron energy range

Abstract

Cross sections of the $^{40}\mathrm{Ca}(n,\phantom{\rule{0.16em}{0ex}}{\ensuremath{\alpha}}_{0})^{37}\mathrm{Ar}$ and $^{40}\mathrm{Ca}(n,\phantom{\rule{0.16em}{0ex}}\ensuremath{\alpha})^{37}\mathrm{Ar}$ reactions at five neutron energy points in the $8.50--9.50$ MeV energy region were measured. The monoenergetic neutrons were produced through the $^{2}\mathrm{H}{(d,\phantom{\rule{0.16em}{0ex}}n)}^{3}\mathrm{He}$ reaction based on the HI-13 tandem accelerator of China Institute of Atomic Energy (CIAE). A twin gridded ionization chamber (GIC) was used as the charged particle detector. Detailed simulations were performed to determine the nuclear reaction events and detection efficiencies. Present results are compared with existing measurement and evaluation data, which shows that the evaluation data from all libraries are higher than the measurement data in the $8.50--9.50$ MeV region for the $^{40}\mathrm{Ca}(n,\phantom{\rule{0.16em}{0ex}}\ensuremath{\alpha})^{37}\mathrm{Ar}$ reaction. TALYS-1.9 code was used for theoretical calculations. Calculation results using the TALYS-1.9 code with the adjusted parameters are in agreement with the present measurements, which also show that the compound mechanism predominates the $^{40}\mathrm{Ca}(n,\phantom{\rule{0.16em}{0ex}}\ensuremath{\alpha})^{37}\mathrm{Ar}$ reaction in the $8.50--9.50$ MeV region. Both present measured forward/backward ratios and TALYS-1.9 calculations suggest that the direct and preequilibrium mechanisms are non-negligible for the $^{40}\mathrm{Ca}(n,\phantom{\rule{0.16em}{0ex}}\ensuremath{\alpha})^{37}\mathrm{Ar}$ reaction in the $8.50--9.50$ MeV region.