Exploration of the Phase Diagram of Strongly Interacting Matter at CERN SPS

The NA49 results on hadron production in Pb+Pb collisions at CERN SPS energies from 20AGeV to 158AGeV provided evidence for the onset of deconfinement are presented. They are confronted with new results from the Beam Energy Scan program at BNL RHIC and CERN LHC results. A possible indication of the QCD critical point signatures was also investigated by the event-by-event fluctuations of various observables.A primary conception, status and plans for continuation of this research program at the SPS by experiment NA61 are briefly reviewed. The main physics goals of the NA61 ion program are the study of properties of the onset of deconfinement and search for signatures of the critical point of strongly interacting matter by performing an energy (beam momentum 13A–158AGeV/c) and system size (p + p, p + Pb, Be + Be, Ar + Ca, Xe + La) scan.