An Encyclopaedia of Indian Archaeology v1.c12.s2.1

v1.c12.s2.1

Neutron activation analysis is part of a wide range of nuclear methods of analysis which are used for elemental analysis, particularly for those elements present at trace concentrations (less than 1 part in 10⁶) in sample. It is also used as a micro-analytical technique for major or minor constituents in case only a very limited quantity of sample is available for examination. This aspect is important in the examination of rare archaeological objects. The analysis is used in archaeology to determine the provenance and sometimes, indirectly, the period to which an artefact belongs. The object examined may be a potsherd, a bronze object, a painting or marble. Very small amounts of sample (~50 mg) will suffice for an analysis of a number of elements (typically 10 to 20) present at trace levels. The sample is irradiated in a nuclear reactor such as Apsara or CIRUS reactor along with suitable standards for the elements analysed. As a result of the irradiation the radio-isotopes of the elements which emit characteristic beta and gamma radiation are produced as they decay into stable nuclides. The energy of the radiation is used to characterize the element and its intensity is related to the amount of the element present. From the concentrations of a number of such trace elements in the samples it is possible to examine whether or not a given specimen belongs to a given group which corrresponds to a particular period or locality. Potsherds belonging to different ages like the Harappa [11.3] and other periods and different classes of pottery like the PGW [11.14] and Banas Ware [11.6.2] have been differentiated by the use of this technique. With this technique it is also possible to say whether an object such as a bronze or an oil painting is genuine or fake.