A geometric charge division pad chamber for Au+Au collisions at the AGS

A set of two wire chambers with highly segmented cathode pad readout were designed, fabricated, and implemented as the tracking system upgrade for AGS experiment E877 at Brookhaven National Laboratory. The purpose of these detectors is to identify secondary vertices from gold on gold colissions, to improve particle identification, and to provide tracking information for all tracks upstream of the spectrometer magnet thereby achieving track confirmation. The two upstream tracking chambers are positioned 2 meters from target separated by 25 cm and together represent 0.8% of a radiation length. Each pad plane covers an area of 32 X 5 cm2 and is equipped with 508 active channels providing a position resolution of better than 250 μ horizontally and 5 mm vertically. From this it can be inferred that secondary vertices should be trackable to within 4 mm of the target. Measurements of position resolution, differential non-linearity of the position determination, mean occupancy, and rate stability will be discussed