Multifunctional application of pulse width analysis in a LED-stabilized digital NaI(Tl) gamma spectrometer

Digital gamma ray spectrometers with NaI(Tl) scintillation detectors are, meanwhile, widely used for locating and classifying radioactive radiation sources that represent potential threats. Such systems make use of flash ADCs for successive sampling of the detector output, and DSPs for digital filtering and signal processing. In contrary to "classical" analog spectrometers the sampling of complete detector signals provides information not only on the total amount of light seen by the photomultiplier, but also on the shape of the original light pulse. This paper presents concept and performance of an LED-stabilized digital NaI(Tl) spectrometer exploiting pulse shape or, more precisely, pulse width analysis (a) for an efficient noise and pileup rejection, (b) for discrimination of LED against gamma signals, and (c) for stabilizing the system against gain shifts due to temperature effects