Data acquisition system for angle synchronized γ-ray tomography of rapidly rotating objects

We developed a fast read-out electronics for a gamma ray computed tomography radiation detector for measurements of two-phase flow distributions in rapidly rotating hydrodynamic machines. The electronics operates with a gamma ray detector comprising 320 single scintillation detector elements working in pulse counting mode. Digital pulses corresponding to gamma or x-ray absorption events in the scintillation crystals are counted with electronics implemented fully parallel in field programming gate array (FPGA) electronics. Data from these counters can be transferred to the measurement PC via a USB 2.0 interface. The design aim for the data acquisition electronics was to acquire data that then could be reconstructed as tomograms with 2 mm spatial resolution from objects rotating as fast as 1200 rpm. This requires approximately 800 tomographic projections during a single revolution in 50 ms. This aim has been achieved with an optimized read-out electronics that is able to transfer the data of all detector counters within 23 mu s to the PC. As an example, in this paper we demonstrate the capability of the measurement system to reconstruct gas distributions in the turbine region of a stirred tank reactor at a stirrer speed of 1200 rpm.