MPPC Photon Sensor Operational Experience in CMS

The CMS Outer Hadron Calorimeter (HO) is the first large scale hadron collider detector to use SIPMs. To build the system we purchased and measured 3000 Hamamatsu MPPCs. 1656 channels of MPPC with 40MHz readout have currently been installed into CMS. We report on comparisons of in situ and vendor supplied measurements. We present results on in-situ working point optimization by IV scanning and temperature vs V scanning. We have developed several techniques for determining the breakdown voltage in situ. We compare the performance of each technique and its success in working point optimization. We present results on gain, noise, and cross talk monitoring. We present results on overall system stability.