Selection and testing of 2000 photomultiplier tubes for the CMS-HF forward calorimeter

The CMS-HF forward calorimeter has specific requirements for the construction and the operation of the detector. The phototubes suggested by several manufacturers were tested and Hamamatsu R7525HA photomultiplier tube conformed best to these requirements. About 2000 PMTs were needed in the HF calorimeter. The timing, dark current, and relative gain values of these 2000 phototubes were measured and organized into a database. Single photoelectron spectrum resolution, absolute gain versus high voltage, and the lifetime were measured on a small sample. Except a few phototubes with unacceptably high dark currents, all the tubes were well within the specifications.