Evaluation of charge -sharing effects on the spatial resolution of the PICASSO detector

A double -layer "edge-on" silicon microstrip detector has been designed and realized in the frame of the PICASSO (Phase Imaging for Clinical Application with Silicon detector and Synchrotron radiatiOn) project at the SYRMEP (SYnchrotron Radiation for MEdical Physics) beamline of Elettra (Trieste, Italy). The detector meets the requirements for synchrotron radiation mammography with patients inregarding: (a) size, since it covers the full beam width (210 mm); (b) spatial resolution, determined by the 0.05 mm strip pitch; (c) single-photon counting capabilities, because it is able to handle more than 106 photons/(pixel x s); (d) contrast resolution, thanks to a threshold trim DAC that equalizes the channel sensitivity; (e) efficiency, due to the high absorption in the 15-20 mm sensor depth. Experimental measurements evidence charge sharing, though not compromising the spatial resolution. (C) 2009 Elsevier By. All rights reserved.