Evaluation of segregation in Roman sestertius coins
Three brass sestertius coins from the reign of Gordian III were imaged at the Oak Ridge National Laboratory’s neutron imaging beam, CG-1D, at the High Flux Isotope Reactor. Tomography results showed a gradual variation in neutron attenuation from one side of the coins to the other or toward the center of the coin. Linear neutron attenuation values calculated from the neutron radiographs, as well as micro-XRF results, suggest that this gradual variation in neutron attenuation is associated with elemental segregation within the coins. The difference in segregation patterns between the coins implies two types of casting methods were utilized to form the coins—vertical and horizontal casting methods.
A portion of this research used resources at the High Flux Isotope Reactor and the Spallation Neutron Source, DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory (ORNL). The authors are thankful to the VULCAN team at ORNL for their assistance in the collection of neutron diffraction data presented in the supplementary material. Another portion of this research was conducted at the High Temperature Materials Laboratory, which is a DOE Office of Science User Facility. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE0228243. Funding was also provided by ORNL Higher Education Research Experience (HERE) Fellowship. The authors are thankful for collection loans from the Joukowsky Institute for Archaeology and the Ancient World.
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