Count rate performance and deadtime analysis of the new 3D PETRRA PET camera

We report on the count-rate performance of the unique PETRRA positron camera at activities up to 60MBq. The camera consists of two large area detectors, each comprising a tiled array of 10mm thick BaF2 scintillation crystals interfaced to a multi-step avalanche chamber filled with 4.2mbar of pure TMAE vapor. Preliminary results demonstrate coincident count rates of over 80kcps for a cylindrical (20x20cm3) phantom with 50MBq of F-18 in the field-of-view using a 20ns coincidence time window. Each component of the readout cycle has been characterized in terms of dead-time loss. The camera's dead-time related count loss is well-described by a paralysable model with a dead-time of ~500ns. Other sources of count rate loss are also discussed.