LXIX. A heavy particle selector

Abstract

A system of Geiger counters and a Čerenkov light detector is described which responds selectively to the passage of slow cosmic ray particles heavier than about 550 electron masses. It has been shown to count at a rate consistent with the known flux of sea. level protons, and cloud chamber photographs show that at least 80% of the counts are caused by protons of range less than 170 g cm⁻² lead.