Advanced neutron guide geometry for the near-backscattering spectrometer at J-PARC

Takahashi, Nobuaki; Shibata, Kaoru  ; Sato, Taku*; Nakajima, Kenji  ; Kajimoto, Ryoichi  ; Oikawa, Kenichi   ; Arai, Masatoshi; Schanzer, C.*

A time-of-flight near-backscattering neutron inelastic spectrometer, DIANA has been proposed for the Materials and Life science experimental Facility (MLF) at Japan Proton Accelerator Research Complex (J-PARC). It has been designed to achieve a high neutron flux at a range of low energies, whose wavelength band is between about 1.4 and 6.4 . We have recently decided to attach the instrument to the coupled moderator source beam-line instead of the decoupled source beam-line, in order to achieve highest intensity at the desired wavelength band. On the other hand, a novel focusing analyzer has been theoretically developed and also designed for the instrument. As a result of this work, it is found that a large beam divergence at the sample is acceptable. Therefore, we have reconsidered the guide system in order to maximize the intensity, according to the report about advanced geometries for neutron guides.