Multiplicity counting from fission chamber signals in the current mode
Artikel i vetenskaplig tidskrift, 2016

In nuclear safeguards, estimation of sample parameters using neutron-based non-destructive assay methods is traditionally based on multiplicity counting with thermal neutron detectors in the pulse mode. These methods in general require multi-channel analysers and various dead time correction methods. This paper proposes and elaborates on an alternative method, which is based on fast neutron measurements with fission chambers in the current mode. A theory of "multiplicity counting" with fission chambers is developed by incorporating Bohnel's concept of superfission [1] into a master equation formalism, developed recently by the present authors for the statistical theory of fission chamber signals [2,3]. Explicit expressions are derived for the first three central auto- and cross moments (cumulants) of the signals of up to three detectors. These constitute the generalisation of the traditional Campbell relationships for the case when the incoming events represent a compound Poisson distribution. Because now the expressions contain the factorial moments of the compound source, they contain the same information as the singles, doubles and triples rates of traditional multiplicity counting. The results show that in addition to the detector efficiency, the detector pulse shape also enters the formulas; hence, the method requires a more involved calibration than the traditional method of multiplicity counting. However, the method has some advantages by not needing dead time corrections, as well as having a simpler and more efficient data processing procedure, in particular for cross-correlations between different detectors, than the traditional multiplicity counting methods.

Current mode

Multiplicity counting

Fission chambers

Nuclear safeguards

Fast neutrons

Campbelling techniques

Författare

Imre Pazsit

Chalmers, Fysik, Subatomär fysik och plasmafysik

L. Pal

Magyar Tudomanyos Akademia

L. Nagy

Chalmers University of Technology

Budapesti Muszaki es Gazdasagtudomanyi Egyetem

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

0168-9002 (ISSN)

Vol. 839 92-101

Ämneskategorier

Subatomär fysik

DOI

10.1016/j.nima.2016.08.048