Selective Detectors for High Energy Photons and Electrons

For fast identification of high-energy electrons and photons in heavy backgrounds, a counter was developed consisting of successive layers of lucite and lead. Čerenkov radiation emitted in the lucite slabs is collected onto the photocathode of one 5 inch phototube. The geometry as well as the thickness of inserted lead converters can be adapted to kinematical requirements. At 1 BeV/c incoming momentum, the rejection ratio of e, γ showers vs. π or μ is better than 100:1; i.e., proper discrimination setting will allow rejection of 99% of all π's and μ's, while only 1% of e's and γ's will be lost. Protons make no pulses at all. The response over the face of the counter is uniform. The properties of the counter are checked in detail against the behavior of lead glass Čerenkov counters, and of lead scintillator sandwiches of comparable geometry. Many applications appear to favor this type of counter over others operating on conventional principles.