Experimental investigation of cold neutron spectra and comparison with monte Carlo simulations

In this contribution we present recent results of the JESSICA experiment located at the proton synchrotron COSY at Forschungszentrum Mich. We measured the time-of-flight spectra and determined the energy spectra at T = 20 K for ice, liquid hydrogen, solid methane, mesitylene, methane hydrate and water at room temperature. These materials could/will be used in next generation high power spallation sources. We were able to normalize the measured spectra to the number of incident protons and thus our experiment is an ideal benchmark to validate source terms of moderators. We compared our measured spectra with MCNPX simulations thereby processing newly generated neutron scattering law data S(α,β,T). In the case of water, a comparison with the multi-group transport code MORSE will be presented. We will discuss the observed discrepancies, which will have an impact on the calculation of the neutron-induced radioactivity of specific components, e.g. neutron beam line shutters or the outer shielding in high power spallation sources. (authors)