Inspection of the Roman Treasure Find by Neutron-, Gamma- and X-Ray Radiography and I-NAA

Abstract

Towards the end of 2003 during the archaeological excavations near the village Drnovo on the construction site of the European highway Ljubljana-Zagreb (Croatia) an intact Roman ceramic pot assumed to contain a treasure find was unearthed. The ceramic pot was dated to the second half of the 3rd century. In order to obtain some preliminary information for the archaeologists and to properly conduct the opening and salvaging of the suspected precious contents of the find, non-destructive radiographic examinations using both conventional radiographic techniques (Ir-192 gamma ray radiography and X-ray computed tomography) as well as thermal neutron radiography (NR) and non-invasive Instrumental Neutron Activation Analysis (I-NAA) were performed. The pot was completely filled with earth, had a total weight of over 9 kg and was quite large (outer diameter 20 cm, height 24 cm) and hence presented a demanding task for radiographic examinations. The radiographic techniques provided clear evidence of the presence of a hoard of coins and jewellery and confirmed the assumptions about the treasure contents. The I-NAA gave a clue about the elemental composition of the hoard. The NR complemented the conventional radiography since it revealed that the coins were hoarded in the four separate purses made of organic materials, probably leather. The neutron NDE were performed using small 250 kW Ljubljana TRIGA research reactor demonstrating its capability for applications in archaeology.