Determination of elemental concentrations of antique coins by photoactivation analysis method

Archaeological artifacts are highly precious, and as is known, most of them are priceless. For interpretation of cultural history of humanity, combination of various disciplines together with archaeology has become extremely important. One of the archaeometric researches is analysis aimed at determination of elemental concentrations of archaeological artifacts. The internal structure of the archaeological artifact, in other words its elemental concentration is highly important, because in some way, it has the characteristic finger print of the artifact. In the light of archaeometric researches, various issues such as originality of the archaeological artifact, based on where the origin of artifact, social, political and artistic structures of that era, interaction with other communities and environment can be clarified. Therefore, a non-destructive method of analyzing the element concentration including the innermost parts is of vital importance. Photoactivation analysis method is quite suitable for elemental analyses of archaeological artifacts mainly because of its non-destructiveness and the other properties providing lots of advantage. In this thesis, the elemental analyses for three ancient Roman coins from different periods were performed using photoactivation analysis method for the first time in Turkey. To activate these antique Roman coins studied in this thesis, the bremsstrahlung beams of 18 MeV end point energy obtained through a clinical linear accelerator were used. As a result of activation by bremsstrahlung photons, the photonuclear reactions are induced, and characteristic gamma-rays are emitted during the transitions to the ground states of the radioactive nuclei created by these photonuclear reactions. Then, the gamma spectra can be obtained by counting these gamma photons through a gamma detector and using a gamma spectrometer system connected with this detector. The gamma detector used in this study is a high purity germanium detector. Because the peaks in the gamma spectra have characteristic energies, the identities of elements in the coins can be determined. Besides, three bronze reference materials that have the same geometry with the coins were activated under the same conditions, and the gamma-ray spectra of these reference materials were obtained. While the activation period was about 1 hour, the counting period after a cooling time was about 20 hours. The photonuclear reactions occurring during the experiment were (gamma,n) reaction resulting in a single neutron separation from the nucleus, (gamma,p) reaction resulting in a single proton separation from the nucleus and (gamma,gamma-prime) reaction resulting in a isomeric transition. On the other hand, because the secondary neutrons occurred due to the interaction of the bremsstrahlung photons with the other material in the accelerator, neutron capture reaction (n,gamma) was also observed. As a result of qualitative analyses, presences of Sn, Pb, As, Sb and Cu elements were determined in the coins. The elemental concentrations of reference materials were also known through the analyses performed by Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Thus, the quantitative analyses for the sn and Cu elements in the coins could also be performed, and the elemental concentrations of these two elements were calculated. In the light of these results, it was shown that the photoactivation analysis method is comparable with the other elemental analysis methods, and it is usable especially for non-destructive analyses.