Luminescent detectors of ionising radiation

At present in slow neutron imaging an active layer of an imaging plate IP contains a mixture of storage phosphors, usually BaFBr:Eu²⁺ used for imaging of X-rays, and a neutron converter material, usually Gd ₂O₃, LiF. A novel Li-containing luminescent material perspective for a direct neutron conversion and storage is discussed. Irradiation of LiBaF₃ crystals results in generation of Frenkel defect pairs and creation of F-type centres responsible for three absorption bands in UV-and visible spectral region. Because photo-stimulation in each of these absorption bands leads to bleaching of induced absorption, the F-type colour centres are convenient for storage of radiation dose. Photo-stimulated decay of F-centres causes recombination luminescence of impurity centres. Thermoactivated decay of F-type centres is governed by ionic process. The thermal stability of F-centres at RT and consequent material storage characteristics can be improved by doping of the LiBaF₃ with heterovalent oxygen impurities. The obtained radiation energy storage, photo- and thermostimulated read-out characteristics justify that LIBaF₃ is a suitable active media for imaging of slow neutrons.