The Neutron Induced Gamma-Ray Reactions in Calcium in the Energy Range 4.85≤ E_n ≤8.05 MeV

Gamma-ray spectra have been obtained for reactions involving neutron interactions with a sample of natural calcium. Gamma rays were observed which are associated with the reactions ⁴⁰Ca(n,n’γ)⁴⁰Ca, ⁴⁰(n,pγ)⁴⁰K, ⁴⁰Ca(n,αγ)³⁷Ar, and ^42,44Ca. Incident neutron energies wereE_n= 4.85, 5.4,6.45, 7.0, 7.5, and 8.05 MeV, and the scattering angle was θ_γ = 125 deg. The gamma rays were detected using a 45-cm³ coaxial Ge(Li) detector placed 100 cm from the sample; time-of-flight was used with the gamma-ray detector to discriminate against pulses due to neutrons and background gamma radiation. The sample was 20 g of natural calcium metal in the form of a right circular cylinder. The incident neutron beam was produced by bombarding a deuterium-filled gas cell with the pulsed deuteron beam of appropriate energy from the ORNL 6-MV Van de Graaff. The resulting neutron beam was monitored using a scintillation counter; a time-of-flight spectrum from this detector was recorded simultaneously with the gamma-ray data. These data have been studied to obtain absolute cross sections for production of gamma rays from calcium for the incident neutron energies. More than 50 gamma rays were correlated with transitions among the residual nuclei; these assigned gamma rays have >90% of the total gamma production cross section for E_n ≤ 6.45 MeV. All unplaced gamma rays have small cross sections and are most likely associated with transitions in ⁴⁰K. The cross sections have been compared, where possible, with previously measured values and with results of the most recent evaluation for calcium with generally good agreement. Several important differences with previous data are discussed.