STUDIES ON A 300 K PIXEL DETECTOR TELESCOPE

Four silicon pixel detector planes are combined to form a tracking tel escope in the lead ion experiment WA97 at CERN with 290 304 sensitive elements each of 75 mu m by 500 mu m area. An electronic pulse process ing circuit is associated with each individual sensing element and the response for ionizing particles is binary with an adjustable threshol d. The noise rate for a threshold of 6000 e(-) has been measured to be less than 10-(10). The inefficient area due to malfunctioning pixels is 2.8% of the 120 cm(2). Detector overlaps within one plane have been used to determine the alignment of the components of the plane itself , without need for track reconstruction using external detectors. It i s the first time that such a big surface covered with active pixels ha s been used in a physics experiment. Some aspects concerning inclined particle tracks and time walk have been measured separately in a beam test at the CERN SPS H6 beam.