Large-System Experience with the ASD-8 Chip in the HERA-B Experiment

The ampliier-shaper-discriminator chip ASD-8, developed by the University o f P ennsylvania for drift chamber applications in high rate environments, is used in large detector systems in the HERA-B experiment. We report on the results of tests performed on some 25 000 chips and on the design and tests of the PC-boards. The so far largest system employing ASD-8 chips is the HERA-B Outer Tracker with about 120 000 drift chamberchannels. We present rst experience with the grounding scheme, noise suppression and the slow c o n trol system as well as rst measurements with the full readout chain in the HERA-B experiment.