Speaker
Mr
Hideyoshi Ozaki
(Tohoku university)
Description
The Kamioka Liquid-scintillator Anti-Neutrino Detector (KamLAND) at Kamioka-mine in Japan, witch has been taking data since Jan 2002, has detected reactor neutrinos and geo-neutrinos using 1,000ton ultra-pure liquid scintillator. The Outer Detector (OD) is a 3,200ton water Cherenkov detector with 225 20-inch photomultiplier tubes (PMTs). The OD is a cosmic ray-muon veto counter and suppresses muon-induced neutrons to enter the liquid scintillator inner detector (ID).
The muon tagging efficiency of the OD had gradually decreased since 2010, which was caused by gradual failure of 20-inch PMTs. To prevent increasing neutron backgrounds, we launched on OD refurbishment in Jan 2016. The 225 20-inch PMTs that were reuse of the Kamiokande-PMTs were replaced with 140 new 20-inch PMTs. At the relatively low sensitive region, the photo-coverage was enhanced and high reflective tyvek sheets were added.
We present a report of OD refurbishment work and the latest data of the new OD.
Author
Mr
Hideyoshi Ozaki
(Tohoku university)
Co-author
Prof.
junpei Shirai
(RCNS, Tohoku University)
