Using Negative Muons as a Probe for Depth Profiling Silver Roman Coinage

Heritage

Kevin Butcher¹  George Green¹  Don M. Paul²  Bethany V. Hampshire²  Adrian D. Hillier³  Katsu Ishida⁴ 

[1] Department of Classics and Ancient History, University of Warwick, Coventry CV4 7AL, UK;Department of Physics, University of Warwick, Coventry CV4 7AL, UK;ISIS Neutron and Muon Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, UK;RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198, Japan;

关键词: muon;    non-destructive;    elemental;    analysis;    silver;    Roman;    coin;   

DOI  :  10.3390/heritage2010028

来源: DOAJ

【 摘 要 】

Debasement of silver Roman coins is a well-known phenomenon and understanding the quality of ancient silver coinages can provide an idea about the underlying fiscal condition of the issuing states. These coins are made from a silver-copper alloy, the surfaces of which were deliberately enhanced at the mints by a process of surface-enrichment to give them the appearance of being made of pure silver. Therefore, any surface analysis would provide a composition of the silver-copper alloy that would not be representative of the original alloy from which the coin blank was made; the result would be too high in silver. However, the bulk of the sample, the interior, should provide a composition that is true to the original alloy. Elemental analysis using negative muons has been used to provide a depth dependent compositional, completely non-destructive analysis of a silver-copper alloy denarius of the empress Julia Domna datable to 211⁻217 CE. The composition of the coin, beyond the surface enrichment layer, is 51 ± 1.8 % copper and 49 ± 1.9% silver, taken at a muon depth of 402 ± 61 µm. The surface enrichment layer is approximately 190 µm thick.

【 授权许可】

Unknown