Sensitization and radiation hardening of the photostimulable X-ray storage phosphor CsBr:Eu2+

The X-ray storage phosphor CsBr:Eu2+ in form of needle image plates is believed to be a promising alternative to the granular BaFBr:Eu2+ with regard to PSL yield and spatial resolution. Unfortunately, CsBr:Eu2+ exhibits poor radiation hardness, which is caused by a migration of europium ions initiated by naturally existing defect centers like (Eu2+-V-Cs)-centers and X-ray generated M-Eu-centers. It will be shown that the formation of (Eu2+-O2-)-dipoles at the expense of (Eu2+-V-Cs)-dipoles, incorporated by thermal annealing in O-2-containing and humid atmosphere, does not improve the radiation stability. There is, however, a strong improvement in the radiation hardness by codoping of CsBr:Eu2+ with lithium ions, which is accompanied by a complete suppression of the previously observed M-Eu-center formation.