M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)
Analysis - BALLA Márta, BÉRCZI János, KEÖMLEY Gábor, ROSNER Gyula, GABLER Dénes: Provenance studies of ceramics by neutron actiwtion analysis
Choice of the material to be investigated and of the measuring method Roman terra sigillatae were chosen as an initial material. This type of ceramics has a definite archaeological basis, its manufacture is well-known, the material is well determined so we could check the results of the initial investigations. As this type of ceramics belonged to import goods in ancient times it can be found in every province of the Roman Empire, it is analysed in several laboratories so there is opportunity for international comparison. When analysing the material of various workshops we have the possibility to answer important historical and economic-historical questions. After having studied the sigillatae with good results we extended our examination to the material of ceramics of the Avar cemeteries and settlements of the Szekszárd area. With regard to the social conditions of the Avar ethnic group living in 6-9th centuries, this territory is of great importance. Provenance study, i. e. grouping the samples according to the workshops and their chemical composition, makes demands on the analytical method used. The chemical composition marks the geological-geochemical antecedents of the raw material and the phases of manufacturing, too. This is especially true for minor and trace elements. The change of concentration of these elements is not restricted by stoichiometrical rules in respect of the principal components (Al, Si, K, Mg, 0). While the concentration of Si, Al, etc. and the different clay-minerals (argils) which are characteristic in layer structures can vary over a relative small range without the structure disintegrating, the interlayer cations are very changeable both quantitatively and qualitatively. That is why we feel that the determination of trace elements is more important than that of the main components since their greater variability assumes more certain separation. According to the above mentioned facts there is another logical demand, i. e. analyses must give information on more elements and groups of elements so as to get an overall picture about the periodic system. The third important requirement is that analyses, coming from the nature of the problem, should be carried out in large series, too, e. g. phases from the preparation of samples to the results received should not contain processes demanding much time and work.The aim is to apply a well automatized measuring method which assumes a sensitive determination of elements at the same time ensuring the objectivity, reliability and reproductivity required by the task. As the following description will show neutron activation analysis can satisfy all the requirements mentioned above. This is the most widespread analytical method applied in studies on the provenance of ceramics. However there is a disadvantage: 50-100 mg of a sample must be taken from the material to be studied and after the examination the sample remains radioactive for a long time . Analytical procedure The essence of the method is the irradiation of the examined sample in a certain neutron"source (generally in a nuclear reactor) thus producing the radioactive isotopes of the elements in the sample by the nuclear reactions. In thermal nuclear reactors the most probable interaction between the stable isotopes of the sample and neutrons is the (n, 7) reaction. The radioactive products of this reaction can be used for analytical purposes. The basis of the qualitative analysis is to determine the energy of the gamma-quanta coming from the examined radioactive isotopes. The measurement of the activity is used for the quantitative analysis. The activity (A) - the number of disintegrated nuclei per time unit — is in a well-defined correlation with the quantity of the certain element. The activity of the isotope produced from the element of mass, m irradiated by thermal neutrons for the time t^r can be obtained from the following expression (after cooling time t c ):
