Use of an improved signal processing to identify a neutron source from the measures obtained with a shift register system

Once known the composition of a Pu, a way for verifying the content of a sample is the detection of multiplicities on neutronic coincidences obtained with a shift register system (SCRD). Such a system provides two laws of coincidences probability for neutrons detected within two gates triggered independently and by neutron themselves. After a brief presentation of the mathematical model of the detection system, the paper describes some experiences in which the SCRD system produced an assessment for fission neutrons and for (α,n) neutrons emitted by a source, without any other information except countings. For instance, this model shows how to separate a Pu 240 source from a Cf 252 source whereas a classical calculation, based on total counting and real coincidences, does not allow discrimination. The calculation shows that usual statistics are sufficient to take the multiplicative effects into account