14.7-MeV Neutron Capture Cross-Section Measurements with Improved Activation Technique

The cross section of the ¹¹⁵In(n,γ)^116mIn reaction for 14.7-MeV neutrons has been determined by measuring the gamma rays following the decay of the metastable (T_½= 54.15 min) first excited state of ¹¹⁶In. An improved activation technique has been developed, resulting in much lower corrections due to secondary low-energy neutrons than in previous experimental arrangements. The corrected activation capture cross section at 14.7 MeV is found to be 0.83 ± 0.06 mb.