The development of multiwire drift chambers for high energy physics

Abstract

An array comprising eight multiwire drift chambers has been developed and installed in the g-2 muon storage ring at CERN with the main objectives being to measure the circulating beam profile and the momenta of decay electrons. Constructional design features include narrow framework and an extremely thin curved end member, the latter having been converted into a sensitive drift space. Prototype models of the chambers have been used to select the operating parameters and to investigate the general properties and capabilities of such detectors. Argon(90%) and Methane(10%) has been chosen from several gas mixtures tested and has been used extensively throughout this work. Prototype and production. chambers have been operated in the e(^+) accelerator beam at the Daresbury Laboratory using a computerised data acquisition system and spatial resolutions of the order 100 to 150 µ/m have been recorded in magnetic fields up to 7.5 KGauss. This system has also enabled a qualitative study of certain simulated g-2 conditions.A simple model based on classical equations has been used to select an electric field, configuration, which enables good operation in a strong non-uniform magnetic field up to 14.75 KGauss, and to predict the behaviour of drifting electrons in such an environment. The operation of the chambers under experimental conditions has been studied, and initial results from the storage ring are discussed together with proposed future work.