High-Accuracy Localization of Minimum Ionizing Particles Using the Cathode-Induced Charge Centre-Of Read-Out

A measurement of the analogue centre of gravity of the induced charge distribution on cathode planes of multiwire proportional chambers allows the localization, in two dimensions, of the ionizing event. This paper describes the localization properties of such a method in the detection of minimum ionizing particles, and in particular the effect of ionization statistics and δ electrons. For a beam perpendicular to the chamber plane, accuracies of around 60 μm rms are obtained in the direction along the anode wires, and of 200 μm in the direction perpendicular to them. A separate measurement of the anodic drift-time allows improvement of the last measurement reducing it to 120 μm rms. The multitrack coupling ambiguity is also discussed.