Čerenkov Counters with Thin Lucite Radiators

Abstract
Čerenkov counters are described which we have used successfully in measurements of the flux of primary cosmic‐ray alpha particles. They consist of cylindrical Lucite radiators 2.5 cm thick viewed by end‐window photomultipliers. Fast singly charged particles that pass through the effective area in directions roughly parallel to the counter axis give pulse‐height distributions with 35–45 percent relative width at half‐maximum for effective areas up to 60 cm2. An analysis of factors that influence the resolution of Čerenkov counters is given.