  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-detector probability generating functions of the kernel and the source is
obtained considering the contribution to detectors statistics of both the
pulsed source and the intrinsic neutron source. An expansion in
alpha-eigenvalues is derived for the final solution, which permits to take into
account the effect of higher harmonics in subcritical systems. Further,
expressions corresponding to the fundamental mode approximation are compared
with recent results from experiments performed under the MUSE-4 European
research project.
