The CMS fast beams condition monitor back-end electronics based on MicroTCA technology

Abstract

The Fast Beams Condition Monitor (BCM1F), upgraded for LHC Run II, is used to measure the online luminosity and machine induced background for the CMS experiment. The detector consists of 24 single-crystal CVD diamond sensors that are read out with a custom fast front-end chip fabricated in 130 nm CMOS technology. Since the signals from the sensors are used for real time monitoring of the LHC conditions they are processed by dedicated back-end electronics to measure separately rates corresponding to LHC collision products, machine induced background and residual activation exploiting different arrival times. The system is built in MicroTCA technology and uses high speed analog-to-digital converters. The data processing module designed for the FPGA allows a distinguishing of collision and machine induced background, that are both synchronous to the LHC clock, from the residual activation products, based on arrival time measurements. In operational modes at high rates, consecutive events, spaced in time by less than 12.5 ns, result in signal pileup. Hence, novel signal processing techniques are deployed to resolve overlapping peaks. The high accuracy qualification of the signals is crucial to determine the luminosity and the machine induced background rates for the CMS experiment and the LHC. The architecture of the back-end electronics and the signal processing techniques will be presented and its performance thus far using data taken in LHC Run II.