A PULSE-GENERATOR SIMULATING GE-DETECTOR SIGNALS FOR DEAD-TIME AND PILE-UP CORRECTION IN GAMMA-RAY SPECTROMETRY IN INAA WITHOUT DISTORTION OF THE DETECTOR SPECTRUM

Commercially available pulse generators for use in gamma-ray spectrosc opy to correct for dead-time and pile-up losses share the problem that the fall-time of the output pulses does not match the fall-time of th e detector pulse. Upon pulse shaping in the main amplifier the pulser' s signals result in a considerable undershoot of the amplifier's outpu t signal, which cannot be restored by the P/Z network. As a result, pe aks in the gamma-ray spectrum are broadened. Moreover, amplitude stabi lity of the generators is often poorer than the overall gain stability of the spectrometer. To overcome these problems a special pulse gener ator has been developed at the Interfaculty Reactor Institute, which s imulates Ge-detector signals. It generates pulses with a constant freq uency of 25 Hz using a crystal oscillator controlled mercury relay. Th e stability of the generator's amplitude and frequency is extremely hi gh and the peak-shapes in the gamma-ray spectrum are not distorted.