Radiation Imaging with Caesium Bromide Storage Phosphors

摘要

This thesis is centred on the development of a new method to prepare semitransparentCsBr:Eu²⁺ imaging plates for high resolution X-ray radiography.Methods of characterising the performance of these plates, and their applicationto dual energy imaging and neutron imaging are discussed.The basic preparation method, based on high-pressure uniaxial compression ofpowder mixtures of CsBr and EuBr₂, produces imaging plates which show goodtransparency and resolution. These imaging plates have a conversion efficiencyof 1.5 pJmR⁻¹mm⁻³ compared to 5.1 pJmR⁻¹mm⁻³ for a commercial needleimaging plate. Water is found to play a critical role in the photostimulatedluminescence activation in CsBr:Eu²⁺ storage phosphors, and imaging platessubsequently hydrated at room temperature have an increased conversionefficiency of up to 11 pJmR⁻¹mm⁻³, better than the commercial material. Amodel has been suggested for the generation of the PSL active site in theimaging plates based on thermomechanical sintering and water-induced crystalregrowth.A precise method for determining the conversion efficiency and stimulationenergy of X-ray storage phosphor materials using an integrating sphere hasbeen developed and used to characterise the materials developed in this thesis.A novel read-out method for storage phosphor imaging plates based on floodillumination and a semi-professional digital camera has also been developedand tested. Good quality X-ray images are obtained and the method showsexcellent promise as a low-cost, portable X-ray imaging system.A stratified detector using CsBr imaging plates has been developed for use indual-energy imaging. Results suggest that it is possible to perform dual-energyimaging with this structure.CsBr:Eu²⁺ imaging plates have been produced with added neutron convertersfor use as thermal neutron imaging plates. An imaging plate with 5 % ¹ºB₂O₃added as a neutron converter has a PSL output 50 % that of a commercialneutron imaging plate. Neutron imaging with these imaging plates has beensuccessfully demonstrated.