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

Abstract

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.

Development of non-destructive isotopic analysis methods using muon beams and their application to the analysis of lead

“…The selected incident energy of the accelerated muon determines the stopping depth in the substance whereby three-dimensional muonic X-ray analysis of the resulting light elements is possible [13,14]. Non-destructive elemental analysis using this method has already been demonstrated for serval valuable samples (e.g., Ninomiya et al and Hampshire et al used this method to determine the internal elemental distribution in archaeological artefacts [14][15][16][17], and Terada et al succeeded in quantifying carbon contents in carbonaceous meteorites [13,18,19]).…”

Characterization of a Continuous Muon Source for the Non-Destructive and Depth-Selective Elemental Composition Analysis by Muon Induced X- and Gamma-rays

“…[15][16][17] used Muon Induced X-ray Emission (MIXE), while the Ref. [18] used Muonic Atom X-ray Spectroscopy (MAXRS); all of which describe the same technique), a non-destructive technique, which was developed more than 40 years ago [14,[19][20][21], has recently been used extensively with pulsed muon beams for elemental analysis [16,18,[22][23][24][25][26][27][28][29][30][31][32][33][34]. The advantage of this technique is that it is able to probe deep into the material, up to a few millimeters, and does not lead to a severe radiation damage of the sample.…”

Muonic X-ray Identification of Nuclear Materials Sealed in a Box

“…Based on these properties, non-destructive and position selective elemental analysis methods have been developed recently using muons. The methods have already been applied in various samples such as archaeological samples and extraterrestrial materials [4,[7][8][9][10].…”