Angle measurement and space resolution in proportional chambers

The problem of measuring the particle projected angle of incidence on the basis of measuring the cluster size, i.e. the number of wires touched by an inclined track, in a proportional chamber is discussed. It is shown that for tracks with large angles of incidence, the space and angular resolution depends in a critical way on the electronics threshold and high voltage setting. With proper operating conditions, the space resolution can be made independent of angle. This means that the resolution perpendicular to the track improves with the cosine of the angle. It is concluded that the projected track angle can be measured directly from the cluster size, with a resolution of typically 10 deg - 20 deg full base width