Experimental Source Performances: Consequences for Proton Pulse Durations and Rep Rates

Abstract

Experimental results on neutron currents and storage times of both ambient temperature H₂O and liquid H₂ cryogenic moderators in various target and reflector environments are presented. These results are compared with measured neutron currents from both a representative thermal beam and the new horizontal cold D² source at the ILL with respect to expected performances of pulsed sources. The results of the spallation experiments are compared with Monte Carlo calculations from Los Alamos. Based on the measured moderator storage times τ the consequences of different proton pulse characteristics on the performance of neutron scattering instruments are discussed in general for both ambient temperature and cryogenic moderators. The possible gain of pulsed operation for time-of-flight and continuous source applications is outlined. In particular, small angle neutron scattering (SANS), a classical technique at a continuous source is taken as an example to show the pros and cons of different source concepts like short pulse spallation sources (SPSS) and long pulse spallation sources (LPSS).