Design, Construction and Commissioning of the Upgrade Radiation Damage Monitoring System of the CMS Hadron Forward Calorimeters

The CMS Hadron Forward Calorimeters cover pseudorapidities between 3.0 and 5.0 being exposed to the highest radiation levels in the CMS detector system. The calorimeter consists of quartz fibers as active media inserted into the steel absorber structure. The radiation damage of the quartz fibers is monitored using dedicated data taking by measuring the fraction of laser light intensity after traversing the quartz fibers. Recently, a new monitoring device based on solid state laser diode technology was designed, constructed and installed. The basic operational integrity was tested extensively prior to installation. The module was integrated into the front-end electronics in a similar way as the Phase I Upgrade LED calibration system. Here we describe the details of the radiation monitoring system and present the commissioning and integration phases.