Characterization of pCVD and sCVD diamond detectors of the beam condition monitors at CMS after an integrated luminosity of 6.3 fb-1

A Beam Loss Monitor system is operational in the LHC to detect potentially damaging particle rates using ionization chambers. The CMS beam condition monitoring system (BCM) uses the same electronics, however, polycrystalline chemical vapor deposition (pCVD) diamond detectors are used instead of ionization chambers, giving a comparable signal for a smaller detector volume. Although diamonds are known to be radiation hard, they can suffer signal loss when placed in intense radiation fields. By comparing the detector current with the integrated instantaneous luminosity, the BCM detector efficiency can be monitored. An observed loss in signal efficiency over the 2011 and 2012 running periods will be presented. After the 2011 run of the LHC and a total of 6.3 fb-1 delivered, one single-crystalline (sCVD) and two pCVD diamonds were removed from the system. Charge collection distance measurements and measurements using the transient current technique were performed on these removed diamonds and will be presented. Results show an increase of polarization effects after irradiation as a possible reason for the observed decrease in detector efficiency.