New equipment for Cherenkov counter at ISR, I-2

Intersection region I-2 at the ISR showing the small-angle spectrometer at upper left and the large-angle rotating spectrometer on the right. The intersection is behind the wire spark chambers at the center of photo 181.12.72. The foil-covered housing appearing above the intersection is part of the ''igloo'' of the muon spectrometer. On either side of the congested collision region were spherical Cherenkov detectors looking like overgrown Christmas decorations. They had been installed by the British, Scandinavian group and were used for particle identification, being particularly concerned with the high momentum particles emerging at wide angles which were among the most surprising observations at the ISR.