Neutron activation analysis of U, Th, K and Rb in archaeological samples from Guayabo (Costa Rica) prior to thermoluminescent dating

Neutron activation analysis has been applied to evaluate the concentrations of U, Th, K and Rb in archaeological samples in view of precise thermoluminescent (T.L.) dating. The experimental conditions including the timing and the Ge detector characteristics are examined. For U and Th, the determinations have been made through both the short radioisotopes (239U and233Th) or through the long-lived daughter nuclei (239Np and233Pa). A factor of 7 between the calculated and observed yields for U is found and discussed. The simultaneous measurement of the 4 elements of interest in samples of about 200 mg is easy achieved.