Elimination of image blurring due to double scatter events in γ imaging MWPC detectors

In multiwire proportional chmabers used with honeycomb lead converters for detecting 511 KeV γ rays from positron annihilation, a source of image blurring is generated by multiple interaction events due to the escape photoelectric x-ray or from the Compton scattered photon. Using the delay line readout method the majority of these double events are eliminated by using the fact that the sum of the time intervals from the prompt anode signal to the signal arrival at each end of the delay line is a constant to within the timing accuracy for a single interaction. Double interaction events produce a time sum which is shorter. Good improvement in image quality is obtained. The observed number of multiple events is larger than calculations would predict.