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We present a well-known concept of pupil-plane WFS, proposed 20 years ago, but developed recently to cope with some typical limitations and problems of using LGS, especially on 40m-class telescopes. The main advantages will be to overcome the truncation problem, to be sensitive to the island effects and, not as a secondary aspect, to be opto-mechanically compatible with the vast part of the existing WFS-LGS system and doable with a smaller format detector. We called it ”Ingot”, looking at its final design, even if we started from a more complicated initial 6 faces concept and here we describe the possible combinations and configurations. We also focus on the characterization of the LGS in the focal volume and the optical/geometrical description of the Ingot WFS. Then we provide a first order comparative analysis with other approaches, by using some relationships to quantify its sensitivity. Finally, we describe the project and the progress of each work-package, in terms of numerical simulations, lab activity and preparation for validation.
