Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session FN: Neutrino Physics III
9:00 AM–11:30 AM,
Friday, October 26, 2018
Hilton
Room: Kohala 4
Chair: Alfredo Galindo-Uribarri, Oak Ridge National Laboratory
Abstract ID: BAPS.2018.HAW.FN.4
Abstract: FN.00004 : Ambient neutron measurement with a He-3 proportional counter in an underground laboratory at the Kamioka Observatory*
9:45 AM–10:00 AM
Presenter:
Keita Mizukoshi
(Osaka University)
Authors:
Keita Mizukoshi
(Osaka University)
Ryosuke Taishaku
(Kobe University)
Keishi Hosokawa
(Tohoku University)
Kazuyoshi Kobayashi
(Institute for Cosmic Ray Research)
Kentaro Miuchi
(Kobe University)
Tatsuhiro Naka
(Nagoya University)
Atsushi Takeda
(Institute for Cosmic Ray Research)
Masashi Tanaka
(Waseda University)
Yoshiki Wada
(Tohoku University)
Kohei Yorita
(Waseda University)
Sei Yoshida
(Osaka University)
Neutron is one of the most serious backgrounds for underground experiments searching for rare events.
Ambient neutron flux in an underground lab. of Kamioka Observatory was measured using a He-3 counter with various moderator setup. Since the detector response largely depends on the spectrum shape, energy spectra of neutrons transported from the rock to the lab. are estimated by Monte-Carlo simulations. The ratio of thermal neutron flux to the total one was found to depend on the thermalizing efficiency in the rock. Therefore, the ratio of the count rate without a moderator to that with a moderator was used to determine this parameter. As a result, the most-likely neutron spectrum predicted by the simulations with the parameters determined by the experimental results was obtained. The neutron flux is (23.52+/-0.68(stat.)+1.87-2.13(sys.)) μ/cm2s.
The result suggests an interesting spectrum shape in high energy region (-MeV), which has not been indicated in previous studies. To clarify that, a scintillator is prepared. The new result will be reported.
*This work was supported by the MEXT KAKENHI Grant-in-Aid for Scientific Research on Innovative Areas 26104001, 26104003, 26104004, 26104005, JSPS KAKENHI Grant-in-Aid for Scientific Research (S) 24224007, (A)16H02189, (A)17H01661.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2018.HAW.FN.4
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