Characterization of 1800 Hamamatsu R7600-M4 PMTs for CMS HF Calorimeter upgrade

The Hadronic Forward calorimeters of the CMS experiment are Cherenkov calorimeters that use quartz fibers and 1728 photomultiplier tubes (PMTs) for readout. The CMS detector upgrade project requires the current Hamamatsu R7525 PMTs to be replaced with 4-anode, high quantum efficiency R7600-M4 PMTs. The new PMTs will improve the detector resolution, as well as the capability of removing fake events due to signal created in the glass window of the PMT. Here, we report the dark current, anode gain, transit time, transit time spread, pulse width, rise time, and linearity measurements performed on 1800 Hamamatsu R7600-200-M4 PMTs.