Design and performance of a high-resolution gamma tomography device

We introduce and discuss the design and performance of a new high-resolution gamma ray tomography device that has been built for the measurement and visualisation of quasi-stationary flow structures in hydrodynamic machines and of gas fraction distributions in thermohydraulic facilities. The gamma tomography system can be operated either with a Cs-137 or a Co-60 source, which allows measurements in radiologically dense enclosures, such as pressure vessels, chemical reactors, or hydrodynamic machines. The detector arc is made of 320 small scintillation detector elements comprising LYSO scintillation crystals with an active area of 2 mm x 8 mm and large area avalanche photodiodes coupled to the crystals. For the photodiode read-out we developed a special charge sensitive pre-amplifier electronics based on a monolithic IC amplifier. This preamplifier stage is followed by pulse shaping and energy discrimination electronics. Data is acquired by fully parallel pulse counting with energy discrimination. For tomographic image reconstruction we implemented a set of analytic and iterative image reconstruction algorithms including filtered backprojection, ART, MART, and SIRT. In the presentation we will especially discuss the performance of the system with regard to density resolution and spatial resolution.