A New time-focusing crystal configuration for an inverted-geometry TOF spectrometer

Takahashi, Nobuaki; Shibata, Kaoru  ; Sato, Taku*; Arai, Masatoshi; Mezei, F.*

An inverted-geometry neutron inelastic spectrometer, DIANA has been proposed for the Materials and Life Science Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC). It has been planned to have three crystal analyzer-banks, pyrolytic graphite PG(002), Ge(311) and Si(111) at near-backscattering configurations to study dynamics of biomolecules and proteins in wide energy transfer and momentum transfer ranges. In general, layout of small crystal-chips on an analyzer-bank is crucial for inverted-geometry spectrometers. We have developed a novel configuration concept of crystal-chips for inverted-geometry TOF spectrometers, which simultaneously achieves time-focusing, spatial-focusing and momentum-correcting abilities. This concept was adopted for the planned spectrometer, DIANA. In the conference, we will discuss the new analyzer layout, and then, will show the focusing performances as evaluated by Monte-Carlo simulations using McStas.