Earlier works have suggested that the energy correlations in a spallation source may influence the neutron noise measurements\r\nin an ADS. For the calculation of this effect not only the generally known and used one-particle spectrum is needed but also the\r\nso-called two particle spectrum, which describes also the energy correlations. Since measured data are not available for the energy\r\ncorrelation of the neutrons from a single spallation event, the physical models of the MCNPX code have been used to investigate\r\nthe effect. The calculational model has been successfully validated with measurements of the number distribution of spallation\r\nneutrons. The simulated one- and two-particle energy distributions and spectra proved that the energy correlations exist and have\r\nan important effect in low multiplicity spallation events and in thin targets. On the other hand, for thick targets this effect appears\r\nnegligible and the factorization of the two-particle spectrum seems an acceptable approximation. Further investigations are in\r\nhand to quantify the actual effect of the energy correlations on the neutron noise measurements.
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