The Novel measuring method in inelastic region; RRM planned for the backscattering spectrometer DNA at the MLF, J-PARC

Takahashi, Nobuaki; Shibata, Kaoru*; Kawakita, Yukinobu  ; Kamazawa, Kazuya*; Yamada, Takeshi*; Nakajima, Kenji  ; Inamura, Yasuhiro  ; Nakatani, Takeshi ; Mezei, F.*; Neumann, D.*; Arai, Masatoshi

A Si-analyzer neutron backscattering spectrometer, DNA, in MLF is the first indirect geometry instrument which chooses the coupled moderator as a pulsed neutron source in addition with a high speed disc chopper as a pulse-shaping device, aiming for high energy resolution with high intensity. The pulse-shaping has the advantage of obtaining a variety of slit opening times. On the other hand, it has the disadvantage of limiting the wavelength band width measured within one pulse-shaped neutron beam. This disadvantage is solved by employing 4 slit discs on the pulse-shaping chopper and generating multiple pulse-shaped incident beams to realize efficient measuring, the so called Repetition Rate Multiplication: RRM technique. An automatic phasing procedure for this RRM technique is planned.