Curved neutron guide of the cold neutron disk-chopper spectrometer at J-PARC

Kajimoto, Ryoichi  ; Nakajima, Kenji  ; Nakamura, Mitsutaka   ; Osakabe, Toyotaka  ; Sato, Taku*; Arai, Masatoshi

Cold Neutron Double-Chopper Spectrometer (CNDCS) is under construction for the spallation neutron source at Materials and Life Science Facility (MLF), Japan Proton Accelerator Research Complex (J-PARC). It is dedicated for research of inelastic phenomena with low energy transfer utilizing an incident energy of meV. It has a 30 m moderator-sample distance () and a supermirror-coated neutron guide tube between the moderator and the sample. The guide tube is curved to eliminate unwanted fast neutron and ray emitted immediately after a proton hits the target. In the present paper, we present the performance of the curved guide of CNDCS obtained by Monte Carlo simulation using McStas. We will report energy dependence of gain in intensity and beam distributions for several kinds of supermirrors, in comparison to the case utilizing a chopper and a straight guide.