First results from ATLAS pixel detectors

The ATLAS experiment at LHC will use several layers of silicon pixel detectors as the innermost elements of the semiconductor tracker. The barrel layers in the central region and the disks in the forward regions will be assembled from detector modules with active areas of ≈10 cm2 each. Every module will contain a silicon sensor with pixels of 50×300 μm2 size and 16 (10) VLSI-frontend chips which are connected to the sensor using a flip chip technology. Each of the overall >108 pixel elements is connected to a low-power, high-speed charge-sensitive preamplifier, a fast discriminator, and a readout system which operates at the 40 MHz rate of LHC. xel system is presented with an emphasis on the readout electronics. The requirements for ATLAS are discussed and compared to the measured performance of the front-end electronics.