Abstract
Abstract
The high-luminosity upgrade of the LHC brings unprecedented requirements for real-time and
precision bunch-by-bunch online luminosity measurement and beam-induced background monitoring. A
key component of the CMS Beam Radiation, Instrumentation and Luminosity system is a stand-alone
luminometer, the Fast Beam Condition Monitor (FBCM), which is fully independent from the CMS
central trigger and data acquisition services and able to operate at all times with a triggerless
readout. FBCM utilizes a dedicated front-end application-specific integrated circuit (ASIC) to
amplify the signals from CO2-cooled silicon-pad sensors with a timing resolution of a few
nanoseconds, which enables the measurement of the beam-induced background. FBCM uses a modular
design with two half-disks of twelve modules at each end of CMS, with four service modules placed
close to the outer edge to reduce radiation-induced aging. The electronics system design adapts
several components from the CMS Tracker for power, control and read-out functionalities. The
dedicated FBCM23 ASIC contains six channels and adjustable shaping time to optimize the noise with
regards to sensor leakage current. Each ASIC channel outputs a single binary high-speed
asynchronous signal carrying time-of-arrival and time-over-threshold information. The chip output
signal is digitized,
encoded, and sent via a radiation-hard gigabit transceiver
and an optical link
to the back-end electronics for analysis. This paper reports on the updated design of the FBCM
detector and the ongoing testing program.