The LHC Fast BCT system: A comparison of Design Parameters with Initial Performance

The fast beam current transformers (FBCTs) for the Large Hadron Collider (LHC) were designed to provide bunch to bunch and turn by turn intensity measurements. The required bunch to bunch measurements together with a large machine circumference call for stringent control of the transmission bandwidth, droop and DC offsets in the front-end electronics. In addition, two measurement dynamic ranges are needed to achieve the required measurement precision, increasing the complexity of the calibration. This paper reports on the analysis of the measurement and calibration methods, discusses theoretical precision limits and system limitations and provides a comparison of the theoretical results with the real data measured during the LHC start-up.