A pixel-like matrix for digital mammography

The SYRMEP (SYnchrotron Radiation for MEdical Physics) collaboration is now developing a microstrip silicon detector with high granularity and high efficiency for research in digital mammography. The project is planning to use a monochromatic X-ray beam, from a bending magnet, of ELETTRA, the synchrotron facility installed in Trieste. The detector is a matrix of pixels, formed by the stacking of different layers of strip silicon pads, with pixel dimensions determined by the pitch and the thickness of the pads themselves. The final detector, an AC-coupled FOXFET-type high resistivity silicon pad, will cover the whole beam region of 4 × 150 mm2. Different pixel sizes have been tested (from 0.5 × 0.5 mm2 to 0.3 × 0.2 mm2). The dead volume in the front of the detector has been reduced in order to reach 80% efficiency in the photon collection. The stacking of the layers has been obtained by means of screen printing deposits of non-conductive glue whose height has been chosen in order to minimize the inter-layer dead region and the cross talk of superimposed pixels. We present here the results of our studies in terms of imaging and the status of the final detector.