Performance and upgrade of the fast beam condition monitor at CMS

The Fast Beam Condition Monitor (BCM1F) is a diamond based particle detector inside CMS. It consisted of 8 singlecrystal chemical vapor deposition (sCVD) diamond sensors on both ends of the interaction point, and was used for beam background and luminosity measurements. The system has been operated with an integrated luminosity of 30 fb-1, corresponding to a particle fluence of 8.78·10-13 cm-2 (24 GeV proton equivalent). To maintain the performance at a bunch spacing of 25 ns and at the enhanced luminosity after the LHC Long Shutdown LS1, an upgrade to the BCM1F is necessary. The upgraded system features 24 sensors with a two pad metallization, a very fast front-end ASIC built with 130 nm CMOS technology, and new back-end electronics. A prototype of the upgraded BCM1F was studied in the 5GeV electron beam at DESY. Measurements were done on the signal shape as function of time, the charge collection efficiency as a function of voltage, and the amplitude as a function of the position of the impact point of the beam electron on the sensor surface. The preliminary results of this test-beam experiment and the status of the newly upgraded BCM1F will be presented.