Evaluation of 400 low background 10-in. photo-multiplier tubes for the Double Chooz experiment

The Double Chooz is a reactor neutrino experiment which measures the last unknown neutrino mixing angle θ13θ13. The Double Chooz experiment uses two identical detectors placed at sites far and near from Chooz reactor cores. The detector uses 390 low-background and high performance 10-in. Photo-Multiplier Tubes (PMTs) to detect scintillation light from gadolinium loaded liquid scintillator. In order to test and characterize the PMTs and to tune operation parameter, we developed two types of PMT test system and evaluated 400 PMTs before installation. Those PMTs fulfilled our requirements and half of them were installed in the far detector in 2009 and physics data have been successfully taken since 2011.