Epithermal neutron radiography and tomography on large and strongly scattering samples

Standard neutron imaging is usually performed with a thermal or cold spectrum, but sometimes, penetration of thermal or cold neutrons is not sufficient for thick samples, so higher energies should be tried e.g. on technical machine parts or on rock samples containing crystal water. A 1-2 mm cadmium filter effectively absorbs all neutrons with energies lower than 0.4 eV, but is relatively transparent for higher energies, including epithermal neutrons. Radiography and computed tomography measurements were recorded at Idaho Nation Laboratory in the USA and Heinz Maier-Leibnitz Institut (MLZ) at the FRM II reactor in Germany. Image quality was improved by better penetration and by filtering out scattered and thermalized neutrons.