Pulse Digitization: Distinguishing between single and multiple gamma ray events with Sodium Iodide Crystals

Gamma ray detection using analog signal processing techniques retains energy information at the expense of information about the type of interaction. However, by digitizing signals from gamma-ray detectors, we can distinguish events on the basis of interaction type, which can be used to reduce background noise. In particular, we would like to isolate single gamma-ray events from multiple gamma-ray events, which may sum in coincidence. We used a 14 bit 100MS/s digitizer to store time, energy, and waveform information from a position sensitive NaI detector, using a Co-60 source to provide both single- and double- gamma-ray events. We compared the waveforms from the individual cascade lines and the waveforms of the associated sum-peak to explore the difference in pulse shape between single- and double- gamma-ray events.