Instrumental design and expected performance of coupled-moderator near-backscattering spectrometer at J-PARC

A near-backscattering (n-BS) crystal-analyzer neutron inelastic spectrometer, DIANA, has been proposed for construction at Japan Proton Accelerator Research Complex. It has originally been designed to view a decoupled non-poisoned moderator in order to obtain high intensity and good energy resolution. Recently, we have reconsidered the instrumental parameters including the type of moderator, by performing Monte-Carlo simulations in order to obtain better performance. Among four virtual n-BS spectrometers on different beam sources moderators, a coupled-moderator-source spectrometer has shown the best performance, i.e. compared to the original DIADA design between ninefold and fivefold enhanced intensities have been obtained with 21%-better to 35%-worse energy resolutions.