Year
2016
Abstract
In passive non-destructive assay, estimation of sample parameters is traditionally based on multiplicity counting using neutron detectors in the pulse mode [1, 2]. The method is based on the detection of singles, doubles and triples (S, D and T) rates. The underlying theory was elaborated by B ¨ohnel [3] by introducing the concept of “superfission”, assuming that the internal multiplication of the source neutrons is instantaneous. The purpose of this paper is to see if it is possible to derive an alternative method, which attempts to extract the above S, D and T rates from the signals of fission chambers in the current mode. This can be achieved by combining B ¨ohnel’s concept of superfission with a master equation formalism, developed recently by the present authors for the statistical theory of fission chamber signals [4, 5]. The advantage of such a method would be that it is free from dead-time problems. It is shown that within the assumptions made, of which the most crucial is just the concept of superfission, indeed the S, D and T rates can be extracted from the first three central auto- and cross moments (cumulants) of the signals of up to three detectors. The theory is described and the resulting formulas are listed. The detailed derivations will be published elsewhere [6].