Performance of a large magnet spark chamber

The description of a 60 × 67 × 160 cm3 spark chamber in a 10.5 kG magnetic field and a report on its performance are given. This instrument was used at the CERN Proton Synchrotron for the detection of the neutral (and non-π0) reaction products of π−, K− and p on hydrogen. The sources of the systematic deviations in spark position have been investigated and corrections have been devised to compensate for them. The residual random errors are: 1.1. the rms deviation of individual sparks from the fitted trajectory σy = 0.18 mm in space.2.2. the rms measurement error σy meas = 0.09 mm in space.