A new ion optical system has been developed for the duoplasmatron source of the Cameca IMS 6f instrument. This system improves performance at low impact energies. It consists of a new primary ion extraction system operating in acceleration/deceleration mode and an additional lens. It provides better source emittance matching with the primary column acceptance and a minimization of the space charge effect in the source plasma. The primary beam density in the sub-kilo-electron-volt impact energy range (down to 500 eV) is therefore improved. This article describes the new extraction system, the performance improvements are discussed in terms of beam intensity and density as a function of impact energy, and application examples for B and P shallow profiles are provided. Results demonstrating the benefits of the sample rotation technique for B depth profiling in silicon with low impact energy O-2(+) beam and oxygen flooding are also presented.