The IMS1280 is based on a double focusing mass spectrometer with a large radius magnetic sector (585 mm). The secondary ion optics has been optimized to work at full transmission up to 6000 mass resolution. This very high transmission coupled with ion bombardment of oxygen or cesium allows the measurement of isotope ratios for species at trace level concentrations (U/Pb dating experiments) or for stable isotopes (oxygen or carbon). The automation level and new control of the optics parameters lead to an exceptional reproducibility on isotopic ratio measurements that is not achievable on any other SIMS instruments (0.1permil level external reproducibility).