Design of optimized RC-CR filters for current-pulse operation of fission counters and high sensitivity fission counters for high gamma backgrounds

A calculational procedure was developed to design RC-CR filters for processing current pulses from fission counters in a gamma background ranging from 105 to 6 x 106 R/hr. The effects of noise from the gamma background and the input preamplifier and of the time constant of the fission counter and input cable were studied. Analytical results were in close agreement with experimental data. A pole-zero network was examined as a means of compensating for the time constant of the fission counter and input cable, but its improvement was insignificant. The procedure was expanded to design a high sensitivity, gamma-tolerant fission counter (approximately 10 counts sec-1 NV-1 at 105 R/hr), and the result was a conceptual design with a performance almost equal to a recently developed high temperature fission counter