Abe, K;
Bronner, C;
Hayato, Y;
Hiraide, K;
Ikeda, M;
Imaizumi, S;
Kameda, J;
... Matsubara, T; + view all
(2022)
First gadolinium loading to Super-Kamiokande.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
, 1027
, Article 166248. 10.1016/j.nima.2021.166248.
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Abstract
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 Gd<inf>2</inf>(SO<inf>4</inf>)<inf>3</inf>⋅8H<inf>2</inf>O (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 m<sup>3</sup>/h, extracting water from the top of the detector and mixing it with concentrated Gd<inf>2</inf>(SO<inf>4</inf>)<inf>3</inf>⋅8H<inf>2</inf>O 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 m<sup>3</sup>/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.
| Type: | Article |
|---|---|
| Title: | First gadolinium loading to Super-Kamiokande |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.nima.2021.166248 |
| Publisher version: | https://doi.org/10.1016/j.nima.2021.166248 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions. |
| Keywords: | Water Cherenkov detector, Neutrino, Gadolinium, Neutron |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10209956 |
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