AN ON-LINE SCINTILLATION COUNTER CONTROL SYSTEM

An on-line data collection system was built and used at the Lawrence Radiation Laboratory's Bevatron to measure the charge asymmetry in the decay~-+ + 7T }.1 v.The system records the states of 144 scintillation counters arranged into twelve hodoscopes, and it can test the operation of each counter.Infermation from pulse height analyzers, a digital voltmeter, time-to-amplitude converters, event clock, e.nd scalers was recorded with each event.Using a PDP-9 computer, over 25 million events were recorded on magnetic' tape during the tuning and data phases of the experiment.A CRT, progra~ed to display his tograms and geometrical models of the experimental information as itwas accumulated, was a valuable diagnostic tool allowing rapid visual assessment of both broad hodoscope and specific counter anomalies.The computer's power was greatly expanded by the addition of external control registers, hardware priority resolvers, event matrix logic, additional programmable flags, and input~output transfer request lines, in addition to software priority levels and the usual program interrupt line and peripherals.Inexpensive dual discriminators, nanosecond coincidence gates", testing circuits and new packaging methods were all used in developing this system.