Multiplicity counting using the two- and three point statistics of fission chamber signals – Theory and experimental demonstration

Abstract

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