A large detector for slow K+ mesons

We describe a large detector for K+ mesons of momentum up to about 600 MeV/c. It is suitable for use in a multiparticle spectrometer for selecting events in which a slow K+ is produced. It consists of layers of scintillation counters and brass absorbers. The method of selection relies on the detection of delayed secondaries from the decay of stopped kaons. The K+ detection efficiency depends on the desired rejection level of other particles: for example, it is 51% with a rejection factor of 120 against π+ and 33% with a rejection factor of 3×104.