Uniformity of response of the LHC1 large area pixel detector system

The uniformity of discriminator threshold and the precision of internal delay have been studied on single `Omega3/LHC1' pixel readout chips and on arrays of 24 chips containing 48 768 active pixels. On single chips we measured a threshold variation of 400e−r.m.s. for a mean threshold setting of 4000e−. The internal delay distribution shows a standard deviation of 6ns on a single chip and 16ns on the large arrays, after applying a 3-bit delay adjustment. These results, obtained using an electrical stimulus, were confirmed by tests in a beam of high-energy particles.