Sensitization and radiation hardening of the photostimulable X-ray storage phosphor CsBr:Eu~(2+)

摘要

The X-ray storage phosphor CsBr:Eu~(2+) in form of needle image plates is believed to be a promising alternative to the granular BaFBr:Eu~(2+) with regard to PSL yield and spatial resolution. Unfortunately, CsBr:Eu~(2+) exhibits poor radiation hardness, which is caused by a migration of europium ions initiated by naturally existing defect centers like (Eu~(2+)-V_(Cs))-centers and X-ray generated M_(Eu)-centers. It will be shown that the formation of (Eu~(2+)-O~(2-))-dipoles at the expense of (Eu~(2+)-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:Eu~(2+) with lithium ions, which is accompanied by a complete suppression of the previously observed M_(Eu)-center formation.