A PIXEL-LIKE MATRIX FOR DIGITAL MAMMOGRAPHY

The SYRMEP (SYnchrotron Radiation for MEdical Physics) collaboration i s now developing a microstrip silicon detector with high granularity a nd 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 slacking of different layers of s trip silicon pads, with pixel dimensions determined by the pitch and t he thickness of the pads themselves. The final detector, an AC-coupled FOXFET-type high resistivity silicon pad, will cover the whole beam r egion of 4 x 150 mm(2). Different pixel sizes have been tested (from 0 .5 x 0.5 mm(2) to 0.3 x 0.2 mm(2)). The dead volume in the front of th e detector has been reduced in order to reach 80% efficiency in the ph oton collection. The stacking of the layers has been obtained by means of screen printing deposits of non-conductive glue whose height has b een chosen in order to minimize the inter-layer dead region and the cr oss talk of superimposed pixels, We present here the results of our st udies in terms of imaging and the status of the final detector.