Photomultiplier noise associated with cosmic rays

The effects of cosmic rays traversing photomultipliers from known directions have been observed and compared with an approximate theoretical treatment of the problem. The efficiency of a simple anti-coincidence technique for excluding such events has been measured. When night sky Cerenkov radiation produced by extensive air showers is being investigated the anti-coincidence technique cannot be used, therefore atmospheric and locally produced Cerenkov signals have been compared as a function of distance from the air shower core for two types of photomultiplier. (author)