The Front-End Electronics of the straw tube tracker for the LHCb experiment

The LHCb experiment is a single-arm spectrometer, designed to study CP violation in B-decays at the Large Hadron Collider (LHC). It is crucial to accurately and efficiently track the charged decay products, in the high-density particle environment of the LHC. For this, the Outer Tracker has been constructed, consisting of ∼55,000 straw tubes, distributed over a sensitive area of 12 double layers of 6x5 m2 each. The detector is foreseen to operate up to 100 kHz/cm per straw in the region closest to the beam. The task of the Front-End Electronics is to provide the precise (0.5 ns) drift-time measurement, at an average occupancy of 5% and at a 1 MHz trigger rate. The tracking procedure requires high-efficiency (low thresholds), while at the same time putting stringent limits on the noise level. The modular detector structure reflects on the FE electronics: 128 channels are read out by one FE 'Box'. The mass production and installation of 450 FE-Boxes is completed. Quality checks have been performed in several stages, at the level of individual boards and at the global level with dedicated test systems mimicking the real detector and capable of simulating all the readout functionalities. At the time of the conference, all FE electronics has been commissioned in situ with test-pulses, cosmic rays and the with first beam events from LHC. No dead channels and very few noisy channels have been found. An upgrade is currently under study, aiming at digitizing and reading out events at each beam-crossing.