In-flight annihilation correction for 511 keV photon spectrometry

Spectrometry based on the 511 keV annihilation photopeak requires the positron source to be surrounded by a suitable absorber material. While this method is well established in the literature, correction for in-flight annihilation losses from the 511 keV photopeak is often found to be neglected. Application to volume sources, such as typically employed in a radionuclide production environment for yield determination and quality control (QC) purposes, is presented. Source strengths obtained by analyzing the 511 keV photopeak are compared with values obtained from characteristic γ-lines for a selection of non-pure positron emitters. Better overall agreement is obtained when in-flight annihilation loss corrections are explicitly performed.