THE READOUT OF THE ATLAS LIQUID ARGON CALORIMETER

The ATLAS liquid argon front-end system will instrument 190000 calorimeter channels, providing low-noise, highly-accurate digital signals to the read-out drivers (RODs) and to the second-level trigger, as well as fast analog outputs to the first-level (LVL1) trigger. The bipolar-shaped ionization signals are sampled at the 40 MHz LHC frequency and temporarily stored into analog memory, during the fixed 2.5 μs LVL1 latency. For each LVL1 trigger, a configurable number of samples (typically 5) are digitized and sent to the ROD via optical links.

Most of the digital components have been redesigned to comply with radiation tolerance requirements. The logic has been implemented in DMILL and/or 0.25 μm ASICs, and feature error-correcting circuitry for protection against single-event upsets. Radiation tolerance studies of the ASICs have been performed using a high-intensity proton beam. Radiation results are presented.