The Raison d’Être of Long Pulse Spallation Sources

Abstract Current accelerator technology allows us today to envisage neutron sources with well above an order of magnitude increased neutron flux for neutron scattering experiments compared to the most intense existing neutron sources, i.e. the high flux reactor at ILL and the spallation sources ISIS, two facilities of complementary use in neutron scattering, with a substantial overlap though. The optimal design of a future, enhanced power source has to tackle the complex relations within the global system accelerator-target-station-neutron scattering instruments. An analysis of the fundamental aspects of these three very different ingredients shows that, depending on the neutron energy, two different technical solutions offer the best performance at lowest costs: (a) conventional spallation sources with short proton pulses in the μs range (SPSS) for hot and epithermal neutrons and (b) long pulse sources with proton beam pulses in the ms range (LPSS) for thermal and cold neutrons. This actually means that ...