Neutron flux and energy resolution of direct-geometry disk-chopper spectrometer AMATERAS at J-PARC

Nirei, Masami; Kofu, Maiko   ; Nakajima, Kenji  ; Kikuchi, Tatsuya*  ; Kawamura, Seiko   ; Murai, Naoki  ; Harada, Masahide   ; Inamura, Yasuhiro  

We investigated neutron flux at a sample position and energy resolution of a direct-geometry disk-chopper spectrometer AMATERAS under various chopper conditions and compared them with simulations and calculations. The measured flux was comparable to other similar spectrometers with high flux. The resolution when using a pulse-shaping chopper was in close agreement with the analytical calculations, including the thickness of the disk chopper, the sample size, and the penetration depth into the detector. It is found that the chopper, placed at the intermediate distance of the primary spectrometer, works as a pulse shaper that optimizes the flux and resolution below the incident energy of 10 meV.