Comparison of PMTs from three different manufacturers for the CMS-HF forward calorimeter

The builders of the CMS forward hadron calorimeter established a set of specifications for readout PMTs that reflected the physics goals and mechanical needs of the CMS experiment. Three manufacturers, Hamamatsu, Photonis (Philips), and Electron Tubes (EMI), provided candidate PMTs based on these initial requirements. Timing, gain, dark current properties, and single photoelectron spectra of these candidate PMTs were measured. Results show that Hamamatsu PMTs (R7525HA) conform best to the specifications of the Hadron-Forward (HF) Calorimeter.