A proportional wire chamber system for beam definition in precision total cross section measurements

Abstract We have developed and extensively used a PWC system in precision measurements of total cross sections at low momenta (0.4–1.1 GeV/ c ) and at high momenta (23–370 GeV/ c ). This “electronic collimator” operated simultaneously in a fast (250 ns) decision making mode, and a slower (0.5 ms) readout mode. The decision making mode utilized adjustable hardwired logic to define acceptable incident beam trajectories and reject multiple beam tracks. A sample of the events was read into an on-line computer for beam tuning, for chamber diagnostics, and for study of the effect of small angle scattering to verify the total cross section extrapolation procedure.