Simulation study on multilayer limited angle scanned electron beam X-ray CT arrangements for two-phase flow measurements

Recently, we presented a limited angle computed tomography approach that utilises a scanned electron beam X-ray source to produce multiple projections of an object. From these projections cross sectional images of the object are reconstructed by using iterative reconstruction algorithms. Tests with static as well as dynamic objects proved that the scan rate of the electron beam allows tomographic imaging with 1000 frames per second at an in-plane resolution of 1 mm. In a simulation study on three-dimensional flow data sets obtained with a fast and high-resolution conductivity wire-mesh sensor under real two-phase flow conditions we have shown, that this approach is capable to recover the in-plane phase structure of the flow. However, two problems arise when this measuring method is utilized for quantitative analysis of two-phase flows. Firstly, by acquiring a time sequence of cross sectional images of one plane in the flow no information about the volumetric structure of the flow can be obtained without knowing the different phase velocities. Secondly, the static arrangement of the X-ray focal spot path and the detector arc in one plane allows only a limited angular range from which projections are available. The missing data leads to artefacts in the reconstructed images which increase with the size and complexity of the imaged structures. For these reasons, simulation studies on different extended measurement arrangements with a two-dimensional beam deflection unit including multilayer imaging have been performed. The presentation will be focused on these different arrangements and their influence on the phase structure recovery of two-phase flows.