 |
| Instrument scientist Floriana Salvemini holds examples of Japanese tsuba, which were imaged with neutron laminography on Dingo. |
Museums and private collectors have had a longstanding interest in Samurai swords because of their workmanship and historical importance.
A young instrument scientist at the Australian Nuclear Science and Technology Organisation (ANSTO) has been applying innovative investigative methods based on neutron imaging to characterise these important cultural artefacts without the need for sampling or invasive procedures.
Floriana Salvemini, who recently joined the Bragg Institute at ANSTO, has studied the composition, assembly methods, and structural variations of Asian and European weaponry using neutrons from the Open Pool Australian Lightwater (OPAL) research reactor in Sydney and several nuclear facilities in Europe to reveal the secrets of ancient technology.
The study was the subject of her PhD in Science for Conservation of Cultural Heritage from the University of Florence with her research activity conducted at Institute of Complex Systems (ICS), part of the National Research Council (NRC) in Sesto Fiorentino.
In simplest terms, neutron imaging involves the direct production of images by transmitting a beam of neutrons through an object onto a detector.
Unlike X- rays, neutrons can penetrate matter deeply, up to 10cm in many materials. A range of contrast-enhancement mechanisms can also be used to map the phase distribution inside objects. 1
Different types of artefacts pose different challenges, and selecting the right instrument and methodology is important to acquire the most useful information.
Comparison of samples at different energies reveals information about the structure and distribution of the material. Salvemini used white-beam tomography, energy-selective tomography and neutron laminography to investigate the metal artefacts.
White-beam tomography is used to characterise the structure and composition of metals. It can provide detailed three-dimensional information through a reconstruction of macroscopic cross sections of the object under investigation. 2
 |
| 3D reconstruction of Suji-Bachi helmet |
Energy-selective tomography is used to acquire information about the morphology and the distribution of phases composed of similar elements.
“The contrast enhancement induced by the selection of an appropriate neutron wavelength was used because it is an important and quantitatively reliable technique for metal characterisation,” said Salvemini.
Neutron laminography is the most powerful method to image flat-shaped objects that are not well suited to conventional tomographic analysis.
Reliable radiography cannot be acquired from angles where the flat side of the object is oriented parallel to the irradiation direction because of high attenuation. In the laminography configuration the sample is tilted to ensure scanning provides a full set of angular projections.
Virtual cross sections of metals using these techniques allow the identification of forge welding or soldering and changes on superficial layer (patination) or any alterations in the body of the sample.
High-resolution images can be constructed from transmission data from these technologies to reveal variations in quality. These images can also be interpreted to determine information about the metallurgical processes used to produce them and to clarify their authenticity.
The Bragg Institute has a suite of neutron beam and x-ray instruments, including the recently commissioned Radiography/Tomography/Imaging Station Dingo.
 |
| Dingo instrument produced an image of the flat tsuba, a hand guard on Japanese swords. |
Salvemini used Dingo to acquire three-dimensional images of the tsuba, a flat horizontal hand guard mounted on a Japanese sword, with white beam tomography and neutron laminography.
The tsuba, which was usually made from metal, was used to prevent the hand from slipping onto the blade during combat. A tsuba may have open worked areas, stylised patterns, and inlays that reflect the period in which they were made. It became a symbol whose purpose was to communicate its owner's social status.
“Dingo provides the best method for the non-invasive investigation of the whole volume of metal objects, including flat objects, such as a tsuba” said Salvemini.
Salvemini measured a slightly elliptical iron tsuba with a tendril design dating from the 18th century and a copper and copper alloy tsuba composed of three layers dating from the beginning of the 17th century.
White-beam laminography is used to produce virtual cross sections that may contain evidence of soldering, surface treatments or other alterations— as it did on the iron tsuba, where a complicated arabesque had been made on it by piercing a single metal disk.
Among the other artefacts studied by Salvemini using neutron diffraction and neutron imaging were a traditional suji –bachi helmet, five katana blades and four Malay kris or keris.
Three-dimensional images reconstructed with white-beam tomography revealed the distinct characteristics of raised ridges on the suji-bachi helmet3, whose peculiar inner structure was revealed to be evolved from the previous ones reported in the literature.
Salvemini needed the new technique of energy-selective tomography to acquire information about the composition and inner structure of metal in the swords.
This methodology provides images with contrast enhancements to determine the grade and positioning of steel. Cross-sectional views revealed the location and quantity of ferrite that were indicative of the production process and period of manufacture.
This methodology provides images with contrast enhancements to determine the grade and positioning of steel. Cross-sectional views revealed the location and quantity of ferrite that were indicative of the production process and period of manufacture.
She also examined and authenticated weapons from the collections of the Ethnographic Museum in Florence, Museo di Storia Naturale Sezione di Antropologia ed Etnologia.
These ancient Malay swords, known as kris or keris were collected by Giovanni Battista Cerruti during an expedition throughout the Indonesian archipelago in the late 19th and early 20th centuries.
These ancient Malay swords, known as kris or keris were collected by Giovanni Battista Cerruti during an expedition throughout the Indonesian archipelago in the late 19th and early 20th centuries.
| Kris sword from Island of Java. |
The art of making these swords, which were believed to have mystical powers, has been closely guarded for centuries. But today neutron imaging is providing insights into how these finely crafted weapons were made.
The distinctive patterns in the blade, Pamor, were made by assembling and forging metal layers of different composition. Iron meteorite could also be used. Thin sheets of metals were shaped into a straight or wavy form and etched. The latter type of kris was distinguished by wave-like undulations (luk) on the blade.
Salvemini’s study of the kris is providing one of the first detailed metallurgical studies of the kris using neutron imaging.4
She hopes to promote the availability of safe and powerful analytical capabilities of neutron instruments at the Bragg Institute to museums in Australia and the Pacific region for the study of cultural artefacts.
1. I. S Andersen, R. McGreevey , and H. Z. Bilheux (Eds) Neutron Imaging and Applications, 2009
2. F. Salvemini,. F. Grazzi, S. Peetermans, M. Gener, E.H. Lehmann, and M. Zoppi Characterization of European sword blades through neutron imaging techniques, Eur. Phys. J. Plus (2014) 129: 202
3. F. Salvemini, F. Grazzi, A. Fedrigo, A. Williams, F. Civita, A. Scherillo, P. Vontobel, S. Hartmann, E. Lehmann, and M. Zoppi, Revealing the secrets of composite helmets of ancient Japanese tradition, The European Physical Journal Plus, August 2013, 128:87
4. K. Mohammed, S. Sulaiman, Z. Ramli, N. H. Shuhaimi, N. A. Rahman, and A. L. Samian The Metallurgical Aspects of the Malay Keris, Research Journal of Applied Sciences (2014) 9 (9) 549-555