The TMT/NFIRAOS LGS wavefront sensing demonstration bench

LGS wavefront sensing on ELTs is challenging. The tip-tilt indetermination, the cone e ect, the star elongation, the sodium profiles fluctuations are the main problems plaguing LGS wavefront sensors. The AO Laboratory at the University of Victoria has build a LGS wavefront sensing test bed scaled for the TMT, reproducing the sodium variations and the whole NFIRAOS wavefront sensing scheme. The details of the bench design are given and the implementation of the wavefront sensing algorithm is presented. This one includes a matched filter, zoom optics control, DM command and truth wavefront sensors management.