Distinctive features in neutronic performance of JSNS

Maekawa, Fujio  ; Oikawa, Kenichi   ; Harada, Masahide   ; Teshigawara, Makoto   ; Kai, Tetsuya   ; Kasugai, Yoshimi  ; Meigo, Shinichiro   ; Oi, Motoki ; Futakawa, Masatoshi  ; Watanabe, Noboru*; Kajimoto, Ryoichi  ; Nakamura, Mitsutaka   ; Torii, Shuki*; Kamiyama, Takashi

Efforts have been made to characterize neutronic performance of JSNS. A NOBORU instrument was mainly used for this purpose while some other instruments were used when needed. The followings were confirmed. (1) Judging from a measured spectral shape, a para-hydrogen fraction in the hydrogen moderator was very close to unity as expected due to introduction of catalyst in a hydrogen circulation system. (2) Measured data for absolute spectral intensity and pulse shapes agreed very well with simulation calculations, and suggested adequacy of the neutron source designs. (3) The world's highest resolution of 0.035 % was recorded at the powder diffractometer SuperHRPD. (4) A total neutron flux of 3 10n/s/cm was confirmed at the chopper instrument 4SEASONS when it was normalized to 1 MW. The flux is the world's highest among existing spallation neutron sources, and is comparable to fluxes at intense reactor sources even in time-averaged value.