Evaluation of Different Gamma-ray Imaging Techniques for Visualisation of Induced Activity in Accelerator Magnets

Activated accelerator magnets were measured with three different types of commercially available gamma-ray imaging devices (pinhole, Compton scattering, and masked type) and the results were compared to simplify a distinction between activated/non-activated areas in the magnet during the decommissioning of an accelerator facility. In general, an activated magnet includes 60Co and emits gamma rays over 1 MeV; however, current devices are not designed to detect such high-energy photons. Our results showed that two devices could identify the location of highly activated areas, although they could not detect the total absorption peaks of the 1173 and 1333 keV photons from 60Co.