Efficiency of neutron tomography in visualizing the internal structure of metal artefacts from Mapungubwe museum collection with the aim of conservation

Abstract

Aim: Estimating physical stability as well as revealing signs of fabrication in metal artefacts via two complementary non-destructive methods, neutron-and X-ray tomography were the main goals of this study. Abstract:To aid conservation management of metal artefacts improved knowledge of the internal structure and degree of corrosion therein is highly desired. In this study, neutron-and X-ray tomography was chosen as two complementary non invasive visualization techniques to study internal structure and corrosion of five representative examples of archaeological metal artefacts from the Mapungubwe museum collection.Tomography was performed at the Neutron Radiography (SANRAD) facility of the S o u t h A f r i c a n N u c l e a r E n e r g y C o r p o r a t i o n w h e r e t h e r m a l n e u t r o n s a s w e l l a s complementary X-rays are conveniently available under one roof. Comparative studies revealed neutron tomography to be generally superior to X-ray tomography due to the enhanced penetration properties of neutrons through the metal objects. In this paper the rich capability of neutron tomography as a non-destructive visualization aid for scientific conservation purposes is introduced and supported by results achieved for the five selected real artefacts.Keywords: neutron tomography/ X-ray/ archaeological metal/ conservation/ corrosion percentage/ Mapungubwe

The Use of Neutron Analysis Techniques for Detecting The Concentration And Distribution of Chloride Ions in Archaeological Iron

“…The objects have a similar mass, and BWB83_163 contains 0.9 mg more Cl than USK_001 (Table 3), but the Cl/Fe ratio of BWB83_163 is eight times smaller than that of USK_001. The use of neutron tomography to estimate the proportion of metal and corrosion product may aid in more accurate determination of Cl using PGAA (Koleini et al 2012). For the above reasons, PGAA is not the appropriate method to determine the absolute Cl concentrations of samples with unknown oxidation states, and it must be used with caution in objects with large metal cores and only small amounts of corrosion product.…”

“…Neutron tomography at the same experimental station can be used to aid interpretation by giving a 3D visualization of the interior of the object which, for metal objects, can be superior to 2D X‐radiography (Koleini et al . ).…”

“…The use of collimators reduces the impinging neutron beam size from its maximum 20 × 20 mm 2 to a minimum spot size of 5 mm 2 to focus analysis in the desired areas. Neutron tomography at the same experimental station can be used to aid interpretation by giving a 3D visualization of the interior of the object which, for metal objects, can be superior to 2D X-radiography (Koleini et al 2012).…”