Abstract:
This thesis is centred on the development of a new method to prepare semitransparent
CsBr:Eu²⁺ imaging plates for high resolution X-ray radiography.
Methods of characterising the performance of these plates, and their application
to dual energy imaging and neutron imaging are discussed.
The basic preparation method, based on high-pressure uniaxial compression of
powder mixtures of CsBr and EuBr₂, produces imaging plates which show good
transparency and resolution. These imaging plates have a conversion efficiency
of 1.5 pJmR⁻¹mm⁻³ compared to 5.1 pJmR⁻¹mm⁻³ for a commercial needle
imaging plate. Water is found to play a critical role in the photostimulated
luminescence activation in CsBr:Eu²⁺ storage phosphors, and imaging plates
subsequently hydrated at room temperature have an increased conversion
efficiency of up to 11 pJmR⁻¹mm⁻³, better than the commercial material. A
model has been suggested for the generation of the PSL active site in the
imaging plates based on thermomechanical sintering and water-induced crystal
regrowth.
A precise method for determining the conversion efficiency and stimulation
energy of X-ray storage phosphor materials using an integrating sphere has
been developed and used to characterise the materials developed in this thesis.
A novel read-out method for storage phosphor imaging plates based on flood
illumination and a semi-professional digital camera has also been developed
and tested. Good quality X-ray images are obtained and the method shows
excellent promise as a low-cost, portable X-ray imaging system.
A stratified detector using CsBr imaging plates has been developed for use in
dual-energy imaging. Results suggest that it is possible to perform dual-energy
imaging with this structure.
CsBr:Eu²⁺ imaging plates have been produced with added neutron converters
for use as thermal neutron imaging plates. An imaging plate with 5 % ¹ºB₂O₃
added as a neutron converter has a PSL output 50 % that of a commercial
neutron imaging plate. Neutron imaging with these imaging plates has been
successfully demonstrated.
