Storage Rings.

The design, construction, and performance of a streamer-chamber system for the study of inelastic proton-proton collisions at the CERN ISR are described. The chambers have specially shaped ground electrodes to accommodate the ISR vacuum chamber and to obtain an almost 4r~ solid angle. Problems arising from the non-fiat electrodes and the insertion of converter plates into the sensitive volume of the chambers are discussed. The high-voltage and gas system are described and in particular the control system for the streamer-chamber memory time which is essential for operation at high ISR luminosities. The optical system, including single-stage electrostatic image intensifiers, is explained. The chambers are triggered on inelastic beam-beam interactions with counter hodoscopes, or on interactions including a photon which is detected in a lead-glass Cherenkov counter located at 90 °. Finally the analysis of the pictures is described.