A prototype of the Laser Guide Stars wavefront sensor for the E-ELT multi-conjugate adaptive optics module M. Lombini, L. Schreiber, I. Foppiani, G. Bregoli, G. Cosentino, E. Diolaiti, J.-M. Conan and E. Marchetti Published online: 24 February 2010 DOI: 10.1051/ao4elt/201005020