Measurement of 56Fe activity produced in inelastic scattering of neutrons created by cosmic muons in an iron shield

We report on the study of the intensities of several gamma lines emitted after the inelastic scattering of neutrons in 56Fe. Neutrons were produced via nuclear processes induced by cosmic muons in the 20 tons massive iron cube placed at the Earth's surface and used as a passive shield for the HPGe detector. Relative intensities of detected gamma lines are compared with the results collected in the same iron shield by the use of the 252Cf neutrons. Assessment against the published data from neutron scattering experiments at energies up to 14 MeV is also provided. It allowed us to infer the qualitative information about the average energy of muon-created neutrons in the iron shield.

► Gamma lines after inelastic neutron scattering in 56Fe are studied.
► Neutrons were produced by cosmic muons in 20 ton iron shield at Earth's surface.
► Results are compared with data obtained by the use of 252Cf neutrons.
► Muon induced neutrons produce just three gamma lines of 56Fe.
► 56Fe levels over 3 MeV are poorly populated.