Low Order Aberrations Compensation by Direct Adjustment of the Reflective Beam Shaper in Slab Laser Topics: Adaptative Optics; High Intensity Lasers and High Field Phenomena; Optical Materials and Devices In Proceedings of the 4th International Conference on Photonics, Optics and Laser Technology PHOTOPTICS - Volume 1, 113-118, 2016 , Rome, Italy