(Milano-Bicocca University, Italy)

Outline: A new equipment for 3D neutron resonance analysis of small objects is now available at the ISIS pulsed neutron source.

One of the key developments in the Ancient Charm project was the construction of a new equipment for 3D neutron resonance analysis of small objects to be used at the ISIS pulsed neutron source. The system is now available for users and was first applied to a number of test objects and archaeological samples. Neutron resonance analysis exploits the unique properties of many isotopes to resonantly capture neutrons at characteristic energies. A combined detector array is used to measure either the gamma-ray emission following neutron absorption or the attenuation of the neutron beam. In the latter case the neutron detector is made from a matrix of 10×10 pixels and the beam attenuation for each pixel is measured as a function of neutron energy thus providing a map of the elemental composition of the object. The neutron energy is determined by measurement of the neutron time of flight; i.e. neutrons are emitted simultaneously by the pulsed source but arrive at different times at the object depending on their energy.
The method is particularly suited for metal artifacts, because many metals (typically Cu, Sn, Zn, Ag, Au, Sb, Pb, As) have strong neutron absorption resonances. Examples of results obtained from test objects of known composition will be shown illustrating the method and its limitations. Both 2D (radiography) and 3D (tomography) analyses will be presented.

Keywords: Neutron analysis, neutron resonances, elemental composition