Radiation Damage to the diamond-based Beam Condition Monitor of the CMS Detector at the LHC

In the Beam Condition Monitor at the CMS experiment at the LHC, CVD diamonds are used as detectors. During Run 1 operation of the LHC, significant reduction of signal efficiency due to radiation damage was observed. The decrease was significantly stronger than expected. The so-called polarization effect is responsible for this signal reduction. Electric field deformations due to trapped charge carriers are shown in measurements using the transient current technique and compared with simulations.