TY - JOUR
T1 - First gadolinium loading to Super-Kamiokande
AU - The Super-Kamiokande Collaboration
AU - Abe, K.
AU - Bronner, C.
AU - Hayato, Y.
AU - Hiraide, K.
AU - Ikeda, M.
AU - Imaizumi, S.
AU - Kameda, J.
AU - Kanemura, Y.
AU - Kataoka, Y.
AU - Miki, S.
AU - Miura, M.
AU - Moriyama, S.
AU - Nagao, Y.
AU - Nakahata, M.
AU - Nakayama, S.
AU - Okada, T.
AU - Okamoto, K.
AU - Orii, A.
AU - Pronost, G.
AU - Sekiya, H.
AU - Shiozawa, M.
AU - Sonoda, Y.
AU - Suzuki, Y.
AU - Takeda, A.
AU - Takemoto, Y.
AU - Takenaka, A.
AU - Tanaka, H.
AU - Watanabe, S.
AU - Yano, T.
AU - Han, S.
AU - Kajita, T.
AU - Okumura, K.
AU - Tashiro, T.
AU - Xia, J.
AU - Megias, G. D.
AU - Bravo-Berguño, D.
AU - Labarga, L.
AU - Marti, Ll
AU - Zaldivar, B.
AU - Pointon, B. W.
AU - Blaszczyk, F. D.M.
AU - Kearns, E.
AU - Raaf, J. L.
AU - Stone, J. L.
AU - Wan, L.
AU - Wester, T.
AU - Bian, J.
AU - Griskevich, N. J.
AU - Ishitsuka, M.
AU - Ito, H.
N1 - Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2022/3/11
Y1 - 2022/3/11
N2 - In order to improve Super-Kamiokande's neutron detection efficiency and to thereby increase its sensitivity to the diffuse supernova neutrino background flux, 13 tons of Gd2(SO4)3⋅8H2O (gadolinium sulfate octahydrate) was dissolved into the detector's otherwise ultrapure water from July 14 to August 17, 2020, marking the start of the SK-Gd phase of operations. During the loading, water was continuously recirculated at a rate of 60 m3/h, extracting water from the top of the detector and mixing it with concentrated Gd2(SO4)3⋅8H2O solution to create a 0.02% solution of the Gd compound before injecting it into the bottom of the detector. A clear boundary between the Gd-loaded and pure water was maintained through the loading, enabling monitoring of the loading itself and the spatial uniformity of the Gd concentration over the 35 days it took to reach the top of the detector. During the subsequent commissioning the recirculation rate was increased to 120 m3/h, resulting in a constant and uniform distribution of Gd throughout the detector and water transparency equivalent to that of previous pure-water operation periods. Using an Am–Be neutron calibration source the mean neutron capture time was measured to be 115±1 μs, which corresponds to a Gd concentration of 111±2 ppm, as expected for this level of Gd loading. This paper describes changes made to the water circulation system for this detector upgrade, the Gd loading procedure, detector commissioning, and the first neutron calibration measurements in SK-Gd.
AB - In order to improve Super-Kamiokande's neutron detection efficiency and to thereby increase its sensitivity to the diffuse supernova neutrino background flux, 13 tons of Gd2(SO4)3⋅8H2O (gadolinium sulfate octahydrate) was dissolved into the detector's otherwise ultrapure water from July 14 to August 17, 2020, marking the start of the SK-Gd phase of operations. During the loading, water was continuously recirculated at a rate of 60 m3/h, extracting water from the top of the detector and mixing it with concentrated Gd2(SO4)3⋅8H2O solution to create a 0.02% solution of the Gd compound before injecting it into the bottom of the detector. A clear boundary between the Gd-loaded and pure water was maintained through the loading, enabling monitoring of the loading itself and the spatial uniformity of the Gd concentration over the 35 days it took to reach the top of the detector. During the subsequent commissioning the recirculation rate was increased to 120 m3/h, resulting in a constant and uniform distribution of Gd throughout the detector and water transparency equivalent to that of previous pure-water operation periods. Using an Am–Be neutron calibration source the mean neutron capture time was measured to be 115±1 μs, which corresponds to a Gd concentration of 111±2 ppm, as expected for this level of Gd loading. This paper describes changes made to the water circulation system for this detector upgrade, the Gd loading procedure, detector commissioning, and the first neutron calibration measurements in SK-Gd.
KW - Gadolinium
KW - Neutrino
KW - Neutron
KW - Water Cherenkov detector
UR - http://www.scopus.com/inward/record.url?scp=85123690317&partnerID=8YFLogxK
U2 - 10.1016/j.nima.2021.166248
DO - 10.1016/j.nima.2021.166248
M3 - Article
AN - SCOPUS:85123690317
SN - 0168-9002
VL - 1027
JO - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
JF - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
M1 - 166248
ER -