The pulsing CPSD method for subcritical assemblies driven by spontaneous and pulsed sources

Stochastic neutron transport theory is applied to the derivation of the two-neutron-detectors cross power spectral density for subcritical assemblies when external pulsed sources are used. A general relationship between the two-detectors probability generating functions of the kernel and the source is obtained. This relationship considers the contribution to detectors statistics of both the pulsed source and the intrinsic neutron one. An expansion in α-modes is derived for the final solution, which permits to take into account the effect of higher harmonics in subcritical systems. Further, the expression corresponding to the fundamental mode approximation is compared with recent results from experiments performed under the MUSE-4 European research project.