[en] A 3 GeV proton Synchrotron is now under completion at the Saclay Nuclear Research Center in France. This machine replaces the former Saturne Synchrotron built in 1958. The lattice type of the new machine is a strong focusing one, and the structure of the magnetic ring is made up of 16 bending magnets and 24 quadrupolar lenses. Due to the small injection energy (20 MeV), it has been necessary to design large aperture magnets. The two accelerating R.F. cavities need a wide range of tuning by ferrites from 0,86 to 8,3 MHz with a peak voltage of 18 kV. The performances of the new machine are better adaptated to the needs of Nuclear Physics. The main features of the extracted protons beam are an intensity of 2.10¹² protons per second at a variable energy from 0,5 to 3 GeV, an energy spread of a few 10^-4 and a small emittance (horizontal approximately 6 π mm.mrd, vertical 25 π mm.mrd). Heavy ions up to N⁷⁺ and polarized particles (H⁺ and D⁺) will be accelerated too, around 10⁹ per pulse on the target. On the experimental areas nine lines are fully equipped and four spectrometers will be set up. The first accelerated beam is expected in October 1978, and the physics experiments should start at the end of this year