Experimental Investigation of Cold Neutron Spectra
and Comparison with Monte-Carlo Simulations
Kay Nuenighoff
Forschungszentrum Juelich GmbH
52425 Juelich, Germany
Email: k.nuenighoff@fz-juelich.de
Phone: +492461-613232
Fax: +492461-61930
Abstract:
In this contribution we like to present recent results of the JESSICA experiment (Jülich
Experimental Spallation Target Set-up In COSY Area) located at the proton synchrotron COSY
at Forschungszentrum Jülich. We were able to measure the time of flight spectra and determine
the energy spectra of cold moderator materials at T=20 K (ice, liquid hydrogen, solid methane,
mesitylene, methane-clathrate) and water at room temperature, which could or will be used in
next generation high power spallation sources. Thus we are able to normalize the measured
spectra to the number of incident neutrons our experiment is an ideal benchmark experiment to
validate source terms of moderators. We compared our measured spectra with MCNPX
calculations processing newly generated neutron scattering law data S(a,b,T). In case of water
also a comparison with the multigroup transport code MORSE will be presented. We will discuss
the observed discrepancies, which will have an impact on the calculation of the neutron induced
activity of specific components, e.g. neutron beam line shutters or outer shielding, in high power
spallation sources.