First results from the ALICE silicon pixel detector prototype

System prototyping of the ALICE silicon pixel detector (SPD) is well underway. The ALICE SPD consists of two barrel layers with 9.83 million channels in total. These are read out by the ALICE1LHCb pixel chip, which has been developed in a commercial 0.25 mum process with radiation hardening by design layout. The readout chip contains 8192 pixel cells each with a fast analog preamplifier and shaper followed by a discriminator and digital delay lines. Test results show a pixel cell noise of about I 10 electrons rms and a mean minimum threshold of about 1000 electrons rms before threshold fine tuning. Several readout chips have been flip-chip bonded to detectors using two different bump-bonding techniques (solder, indium). Results of radioactive source measurements of these assemblies are presented for (90)Sr and (55)Fe sources. Several chip-detector assemblies have been tested in a 150 GeV/c pion beam at CERN where an online efficiency of about 99% across a wide range of detector bias and threshold settings was observed. All preliminary investigations confirm the functionality of the chip and the chip-detector assemblies for the ALICE experiment. (C) 2002 Elsevier Science B.V. All rights reserved.