BEAMGAA with photons — the axial gradient

Abstract

Materials of significant inhomogeneity require big samples to be analyzed. With the exception of very few installations worldwide the near-core neutron irradiation positions are not spacious enough to fulfil this condition. The use of beam geometry activation analysis (BEAMGAA) has actually turned out to be an alternative as the activities obtained are proportional to the product of flux and sample mass. In the case of hard photon radiation delivered by the 30 MeV-Linac of BAM, equipped with a programmable scanner of the electron beam for dose equalization, a nearly uniform distribution could be obtained in a volume of 7 cm×7 cm×2 cm. It is shown that big sample volumes up to 7 cm×7 cm×10 cm can be treated and non-linearities of irradiation can be perfectly taken into account by the self-adjusting method of consecutive correction factors (COCOFA). Nevertheless, the concept of “sliced samples” has to be considered when maximum correctness of the analytical results has to be guaranteed. With the measures described in photon activation analysis a quality level was realized which was not reached hitherto.