PYPS is the pyramid wavefront sensor for the phasing and alignment of segmented mirrors developed in the
framework of the Active Phase Experiment (APE). In this paper we will present the PYPS opto-mechanical
design, and report the experimental results obtained in the Arcetri laboratories prior to its integration in the
main APE bench. A piston-correction closed loop was performed under the presence of emulated turbulence
(D/r0=33 @ 700nm and V/D=1.9Hz), achieving a final piston error of 10 nm rms in wavefront. Two filtering
techniques were developed to average out faster the atmospheric disturbance reducing the required co-phasing
time by two orders of magnitude. We will also present the first experimental results obtained with a synthetic
interaction matrix attaining a final piston error of the same order of magnitude.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.