Developments in particle tracking using the Birmingham Positron Camera

The RAL/Birmingham Positron Camera consists of a pair of MWPCs for detecting the pairs of back-to-back 511 keV photons arising from positron-electron annihilation. It was constructed in 1984 for the purpose of applying PET to engineering situations, and has been widely used for the non-invasive imaging of flow, including extensive studies on geological samples. The technique of Positron Emission Particle Tracking (PEPT), whereby a single positron-emitting tracer particle can be tracked at high speed, was developed at Birmingham and has proved a very powerful tool for studying the behaviour of granular materials in systems such as mixers and fluidised beds. In order to extend its effective field of view, the camera has recently been mounted on a motorised translation stage under computer control so that the motion of a tracer particle can be followed over a length of up to 1.5 m. A preliminary investigation into the feasibility of enhancing the PEPT technique using the singles count rates in the two detectors has also been undertaken.