Abstract: Polycrystalline mercuric iodide films are developed as new detectors in room temperature X-ray imaging. In this paper, 8 different electrode patterns are designed by varying the widths of grid and gap. Finite element analysis is used to simulate the potential distribution of the coplanar-grid detectors. The electrode design of pattern E, with width of grid 150 μm and width of gap 500 μm, is the best. The influence of edge effects resulting from the unsymmetrical electrodes on the potential distribution is discussed. The geometry of electrodes for coplanar-grid detectors is optimized by widening the second grids near edges as shown in pattern N.

Key words: coplanar-grid detector, finite element analysis (FEA), polycrystalline HgI₂