39 tons of gadolinium sulfate has been injected into Super-Kamiokande.
Delivery of 39 tons of gadolinium sulfate octahydrate has been completed and dissolved into the Super-Kamiokande (henceforth SK) at the University of Tokyo Institute for Cosmic Ray Research in Hida City, Gifu Prefecture.
The gadolinium sulfate octahydrate input this time weighs 26 tons and, like the 13 tons input in 2020, is an ultra-pure product with radioactive impurities reduced to the limit (on the order of ppt*). The total weight is 39 tons (16.8 tons as gadolinium) combined with the previous one, and the gadolinium concentration in SK's 50,000 ton tank is 0.03%. This will give us about a 75% chance of capturing neutrons emitted in neutrino reactions such as supernova background neutrinos, and full-scale observations will begin in the future.
For details, please refer to the website of the Kamioka Observatory for Cosmic Particle Research, Institute for Cosmic Ray Research, University of Tokyo.
https://www-sk.icrr.u-tokyo.ac.jp/news/detail/853/
*ppt: parts per trillion