The LUCID 3 detector for the ATLAS Phase-II Upgrade

The measurement of the luminosity in ATLAS at HL-LHC will be of the highest importance to fulfill the precision requirements for most of the physics program of the experiment. It is expected that the upgraded LUCID detector will play a major role in this measurement, both online and offline. In this report, the various options under investigation for the detector layout, electronics and infrastructures are described, together with the prototypes under construction for Run-3 which will guide the choice of the final design for HL-LHC.