MULTIPLICITY COUNTING USING THE TWO- AND THREE POINT STATISTICS OF FISSION CHAMBER SIGNALS – THEORY AND EXPERIMENTAL DEMONSTRATION

摘要

In two earlier papers [1,2] we investigated the possibility of extracting traditional multiplicitycount rates from the cumulants of fission chamber signals in current mode. Thefirst three cumulants were derived for up to three detectors. It was shown that if all neutronsemitted from the sample simultaneusly are also detected simultaneously, the multiplicityrates can be retrieved from the cumulants of the detector current, but the methodbreaks down if the detections of neutrons of common origin take place with a time delayspread wider than the pulse shape. To remedy these shortcomings, in this work we extendedthe theory to two- and three-point distributions (correlations). It was found that theintegrals of suitably chosen two- and three-point moments with respect to the time differencesbecome independent of the probability density of the time delays of detections.With this procedure, the multiplicity rates can be retrieved from the detector currentsfor arbitrary time delay distributions. To demonstrate the practical applicability of theproposed method, pilot measurements are performed. A description of the experimentalsetup and some preliminary experimental results are presented in the paper.