Aligning and testing the ingot wavefront sensor in the lab

The Sodium Laser Guide Star (Na-LGS) on the sky is not point-like, rather cigar-like when launched from the side of a large (or extremely large) telescope. The Na-LGS’s 3D nature gave birth to the idea of a new pupil-plane wavefront sensor that can be deployed in a similar 3D manner - the Ingot Wavefront Sensor (I-WFS). The design of the I-WFS has developed over the last two years, and currently, the ingot prism has 3-faces, creating three pupils. Wavefront sensing can be done using these three pupils themselves as the signals or the slopes generated by the pupils. At the INAF-Padova laboratory, we have realized a test-bench simulating the ELT∗ characteristics to test the I-WFS characteristics and an alignment procedure. We use simulations and lab data to compare, learn, and define a robust alignment procedure. Eventually, we expect to have an entirely automatized alignment procedure using the optical feedback from the I-WFS. In this article, we report the comparison between the laboratory data and the simulations representing (1) the sensitivity measurements of ingot prism misalignment for each degree of freedom with respect to its ideal, aligned position, and (2) the response of the I-WFS to known aberrations using a deformable lens. The final goal is the definition and description of the procedure to align the I-WFS.