Measurement of energy spectra and spatial distributions of neutron beams provided by the ANNRI beamline for capture cross-section measurements at the J-PARC/MLF

Kino, Koichi*; Furusaka, Michihiro*; Hiraga, Fujio*; Kamiyama, Takashi*; Kiyanagi, Yoshiaki*; Furutaka, Kazuyoshi  ; Goko, Shinji*; Harada, Hideo   ; Harada, Masahide   ; Kai, Tetsuya   ; Kimura, Atsushi   ; Kin, Tadahiro; Kitatani, Fumito  ; Koizumi, Mitsuo ; Maekawa, Fujio  ; Meigo, Shinichiro   ; Nakamura, Shoji  ; Oi, Motoki ; Ota, Masayuki*; Oshima, Masumi; Toh, Yosuke   ; Igashira, Masayuki*; Katabuchi, Tatsuya*; Mizumoto, Motoharu*

We measured the energy spectra and spatial distributions of the neutron beam of ANNRI beamline at the Japan Proton Accelerator Research Complex / Materials and Life Science Experimental Facility (J-PARC/MLF). Our research team designed and built this beamline to measure nuclear data with high precision. The measurements were performed on three types of beams provided by the beamline in the neutron energy range of 1.5 meV to 10 keV. The energy spectra show a typical feature of para-hydrogen moderator, and the absolute intensities almost agree with predictions based on both a simulation calculation of the JSNS (Japan Spallation Neutron Source) and a neutron transmission calculation of the beamline. The available neutron intensities at 21.5 m are 7.510, 1.610, and 1.110 n/cm/sec in the energy ranges of 1.5-25 meV, 0.9-1.1 eV, and 0.9-1.1 keV, respectively, under the 17.5 kW JSNS operation. The measured spatial distributions of the beams formed by three different collimators are consistent with those expected from the collimator-system design of the beamline. The beam sizes in FWHM are about 29, 14, and 11 mm for the three different beam collimators. The edges of the spatial distributions are relatively sharp, enabling us to measure the nuclear data successfully.