Analog system for building the first-level triggering signal provided by the hadronic calorimeter of ATLAS detector

The trigger summing system for the hadronic calorimeter of ATLAS is described. This analog summing system aims at building the trigger tower signals, which are used by the first level triggering system of the ATLAS detector for on-line event validation at Large Hadron Collider conditions. The system combines linearly up to six differential signals (50 ns full-width half-maximum), which come from different sampling layers of the calorimeter. The system operates over a wide dynamic range and provides two output signals with driving capabilities for 50Ω loads: the sum of the six input signals, to be used as calorimeter trigger, and the signal coming from the third sampling layer of the calorimeter, which is planned to be used as a muon trigger. Both laboratory and particle beam tests shown the good performance achieved by the system in terms of linearity (better than 2%), dynamic range (10 bits), and pulse transmission capability.