Performance of PMTs for the JSNS2 experiment

Abstract

The JSNS${}^2$ (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) experiment aims to search for neutrino oscillations over a 24\,m short baseline at J-PARC. The JSNS${}^2$ inner detector is filled with 17 tons of gadolinium-loaded liquid scintillator (LS) and both the intermediate ${\hat{I}}^3$-catcher and the optically separated outer veto are filled with un-loaded LS. Optical photons from scintillation are observed by 120 Photomultiplier Tubes (PMTs). A total of 130 PMTs for the JSNS2 experiment were both donated by other experiments and purchased from Hamamatsu. Donated PMTs were purchased around 10 years ago, therefore JSNS${}^2$ did pre-calibration of the PMTs including the purchased PMTs. 123 PMTs demonstrated acceptable performance for the JSNS${}^2$ experiment, and 120 PMTs were installed in the detector.