A negative-curvature nuclear pulse filter

A set of nuclear pulse filters developed by C. H. Nowlin has complex and real poles lying on a straight line of constant o. Two of these filters, one having five poles and one having seven poles, have very desirable noise and pile-up characteristics. This study considers a variation of the above filters in which the poles are located on a line having a negative curvature rather than on a straight line.

This study includes a theoretical analysis of both the noise and the pile-up characteristics of both types of filters. Using one five-pole filter of each type, the cusp factors for the two filters were calculated and found to be approximately equal to 1.13. The pile-up characteristics of the filter having poles on a negative curvature appeared to be better than that of the filter having poles lying on a straight line. Equating the noise performance for two five-pole filters, the ratio of the peak shift at high count rate was approximately l.8 and the ratio of the peak spreading was 1.8.

Although these results were not verified experimentally, pulse-shaping filters with poles lying on a line having a negative curvature may be superior at high count rates to comparable filters having poles lying on a straight line of constant σ.