PULSE RISETIME DISCRIMINATION FOR 3HE COUNTERS

Risetime discrimination is discussed from the point of view of optimizing the experimental conditions of a 3He gas counter for fast neutron spectroscopy. The approach is to transform the pulse risetime into a crossover time (which is easily transformed to an amplitude and stored in a multichannel analyzer), using a double RC differentiating circuit and a crossover pickoff. It was required to maximize accuracy and sensitivity. The behavior of the pertinent factors (attenuation, slope at crossover, sensitivity) was determined as a function of the differentiating time constants T1 and T2, and the pulse risetime constant τ. The relationships T1≧2τ and T2≧5τ are shown to represent an optimized system. © 1969.