Ingot wavefront sensor: from the Fourier End2End numerical simulation to the LOOPS test bench

The Sodium Laser Guide Star (LGS) is an elongated object in a 3D volume. This produces a significant elongation on many of the Shack-Hartmann wavefront sensor spots that the ELT instruments use for wavefront sensing. The Ingot Wavefront Sensor (I-WFS) has been proposed as a possible solution to deal with the 3D nature of the LGS. We developed an end-to-end numerical tool of the I-WFS to perform system analysis of a closed-loop complete system. We considered the generation of the input turbulence, deformable mirror definition and control, and, of course details, of the I-WFS. It needs a 3-Dimensional description to fully take into account the elongation effect across the vertical (propagation) axis. The I-WFS has been simulated similarly to the Pyramid Wavefront Sensor, as a combination of Foucault knife-edge sensors. In parallel to numerical simulations development, we had the opportunity to perform laboratory testing of the I-WFS at the LOOPS Adaptive Optics test bench (at LAM), using a Spatial Light Modulator. This device is able to produce a high definition phase mask that can mimic two-dimensional I-WFS behaviour. In this framework, we report a preliminary discussion both for the simulations and the closed-loop data analysis.