A K+ Detector for Use with a Rapid Cycling Bubble Chamber

A detector system has been made to detect the decay of K+ particles generated in nuclear events in the twenty cycles per second hydrogen bubble chamber at the Princeton-Pennsylvania Accelerator. The purpose of this system is to preview each event to minimize the number of non-productive photographs. Ninety-six (96) large plastic scintillator counters form an array covering 180 degrees of the down-stream side of the chamber. Particle discrimination is done by generating a clock timing pulse from counters placed in the incoming beam which enables a set of coincidence gates driven by individual array counters, in such a period as to exclude outputs due to various prompt particles (i. e. the primary beam or the results of various elastic interactions in the chamber). A second level of gating is required to determine if the interaction has occured during a period in which the chamber was sensitive. The output signal is used to trigger a chamber illuminating flash tube to photograph the event.