Photon Activation Analysis – An Analytical Application Of High-Energy Electron Accelerators

摘要

Photon activation analysis (PAA) was introduced about contemporarily with the other activation analysismethods (neutron, NAA, and charged particle activation, CPAA). Nonetheless, for different reasons, PAA has been ap-plied less frequently than the other techniques mentioned. The incident photon energy should exceed about 12 MeV (ex-cept in some special rare applications) so as to obtain appreciably high activity yields of the product nuclides. Thus, cy-clic electron accelerators (LINACs or microtrons) are used for activation preferably. The predominant photonuclear re-action is of the (y,n)-type. Thus, normally neutron-deficient nuclides are produced. These usually emit gamma rays, an-nihilation quanta and characteristic X-ray fluorescence, all of whom can be used for analytical evaluation. The spec-trometry equipment is the same as used for the other activation techniques (semiconductor detectors, sodium iodide crys-tals in coincidence geometry). Being uncharged high energy photons have a large penetration power, thus do not sufferfrom strong matrix absorption. Although not having a detection power as large as in NAA (in the most cases), PAA of-fers several further convincing advantages, e.g. several elements not or hardly detectable by NAA can be analysed: Tita-nium, nickel, thallium, lead, bismuth and, in particular, the light elements carbon, nitrogen, oxygen, fluorine, phospho-rus. Several typical applications will be described.