Recent Advances in Photomltipliers for Low Light Level Applicaticnis

The measurement of light sources of feeble intensity reguires special detectors. Two new photomultipliers suitable for such measurements are described. The 9870, `bulls-eye´, photamultiplier has a quasi-spherical cathode with nearly 2 ¿ collection efficiency. The cathode shape provides isochronous collection over the photocathode area. This tube is used for large volume Cerenkov detectors. The 9863 is a fast, linear fochsed photomultiplier with a cathode of small effective area, and is used where the light can be suitably focused. The tube has a large dynamic counting range and has general application in photon counting. The low afterpulse performance when used with fast, digital correlators is discussed.