Characteristics of SiPM Photo Sensors for GlueX

The barrel calorimeter of the GlueX detector in Hall D at Jefferson Lab will be instrumented with 3840 large-area (1.2$\times$1.2 cm$^2$) custom silicon photomultiplier (SiPM) arrays manufactured by Hamamatsu Corporation~[1]. These photon sensors have properties similar to vacuum photomultipliers, but are unaffected by high magnetic fields. In our experiment, they will operate in magnetic fields exceeding 1~T. A series of measurements have been carried out by several groups to characterize these SiPMs including the photon detection efficiency (PDE), gain, dark rate, cross talk and after-pulsing at different bias voltages and temperatures. A special study was performed for the first time to separate the cross talk and after pulsing by analyzing ADC spectra with different gate widths. These measurements allow a unique extraction of after-pulsing parameters. We will present a summary of these measurements and the plan for use of these sensors in the GlueX experiment.\\[4pt] [1] F. Barbosa {\em et al.,} NIM A695 (2012) 100.