LUCID (LUminosity Cerenkov Integrating Detector) is the main luminosity monitor of the ATLAS (A Toroidal LHC Apparatus) experiment at the Large Hadron Collider (LHC) and in particular is the only one capable of providing bunch-by-bunch luminosity information, both online and offline, for all beam conditions and luminosity ranges. LUCID-2 refers to the detector upgrade designed to cope with the running conditions to be met in Run-2 (2015–2018): a center of mass energy of 13 TeV, with 50 pp

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... ctions per bunch-crossing on average and a 25 ns bunch-spacing. This report summarizes all changes with respect to the detector deployed in Run-1 (2010–2012), including smaller sensors for higher granularity, new readout electronics for early signal digitization, and a completely new calibration concept guaranteeing long-term stability of the detector response. In addition, the overall detector performance in Run-2 and preliminary results on luminosity measurements are presented.