Neutrons and artefacts
For the first time, neutron images in 3 dimensions have been taken of archaeological artefacts at Oak Ridge National Laboratory (ORNL). Bronze and brass artefacts excavated from the ancient city of Petra, in Jordan were imaged in 3 dimensions using neutrons at HFIR’s CG-1D Neutron Imaging instrument.
The samples that were imaged came from the collections of the Joukowsky Institute for Archaeology and the Ancient World at Brown University. They include an elaborate hanging bronze oil lamp, a large Roman coin, and a standing dog figurine.
Neutron radiograph of an ancient Greek lamp. Image: Oak Ridge Labs
The imaging and analysis resolves questions of object identity and raises many new ones about the techniques and materials that craftspeople used to make these objects. Principal Investigator Krysta Ryzewski, an Assistant Professor of Anthropology at Wayne State University pointed out that they can also examine certain objects to look for trace residues such as oil once burned in the lamp.
The neutron imaging beam is a huge step forward for scholars. “Archaeologists and scientists can obtain relatively little information about the manufacture of archaeomaterials, ancient objects and the materials from which they are constructed, from external surfaces alone,” says Ryzewski. “Very few historical accounts describe the construction of such objects and archaeomaterials, ancient bronzes or ceramic vessels. The only source of information about how these objects were constructed comes from their material properties and composition.”
Archaeological objects are unique cultural resources and earlier analysis often entailed extracting a sample, which meant damage and sometimes even destruction of an artefact. Imaging archaeological objects comprehensively and systematically with neutrons only became possible with the development of the CG-1D Prototype Beamline. Neutron activation analysis and neutron imaging at Oak Ridge means scholars can now conduct detailed, non-destructive analysis of samples.
The control room at the High Flux Isotope Reactor. Image: Oak Ridge Labs
CG-1D data can reveal the raw materials used, manufacturing techniques, historical development of alloys and composite materials and even geological origins of ores and clays, and researchers can also learn about the activities of daily life that such objects served.
Archaeologists can now begin to precisely reconstruct networks and patterns of resource extraction, trade and exchange, environmental impacts of industrial activities on ancient landscapes, and the transmission of craft production traditions over time.