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
The right side of the equation is constant for a given isotope and given irradiational and measuring conditions (reactor, detector) and is called corrected specific intensity: I - N SP SD-Cm For calculating mass m , the multiisotope comparator method — involving the advantages of the absolute and relative method - was applied [7]. Two phases of the comparator technique can be separated. In the first so called standardizing phase the specific intensity ratio of certain elements to the appropriately chosen comparator isotopes is to be detemtined, corrected for saturation and zero cooling time. These are the so called 'Ic-factors" (the comparator is marked with *): k = iüPI* *sp which is constant for a given element-comparator couple and by given reactor and defector parameters In the analytical phase the corrected specific counting rates of the isotopes found in the spectrum can easily be calculated (after determining the specific intensity and knowing the k-factors): *sp : Isp Since: * N ******* SD-Cm the mass, m and the concentration can be simply calculated after deteimining the peak areas, knowing the parameters of the measurement. There are a large number of elements of random distribution in the periodic system that can be determined by neutron activation analysis. This is because the sensitivity of activation by neutrons (cross section) is independent of the chemical character of certain elements, it depends only on the structure of the nucleus It should also be noted that the isotopes of the tight elements fonning the greater part of the most of natural materials, minerals and rocks, either cannot be activated in nuclear reactors or they decay with a very short half life. Thus the elementary analysis gives information on the minor and trace elements, components of minerals and rocks; it was precisely this that was expected from the method. The measurements are carried out in the following steps. The surface of the ceramic article is to be cleaned by a diamond-powdered grinder at the place of sampling. With the help of a conical diamond drill, we take 50—100 mg of powder samples. The samples are heated in a crucible furnace at 900 °C for one hour to bum up the possible organic content or to remove the adsorbed moisture . After cooling, the samples are put into small polyethylene capsules; accurate mass weighing is then carried out. Irradiation is performed in the nuclear reactor of Budapest's Technical University at a thermal neutron flux of 10 16 nnf 2 s" 1 and for an irradiation^ tome of 8-12 hours. Each sample is measured twice: 4-6 and 25-30 days after the irradiation, to ensure optimal measuring conditions
