The present study reports a characterization of a cold plasma jet at atmospheric pressure. It is obtained from a Dielectric Barrier Discharge (DBD). The final aim is to create a soft ionization source which coupled with a Time Of Flight Mass Spectrometer (TOF-MS) permits the detection of species of an analyte present on a surface or injected in the gas flow. In this work a comparison between Neon and Helium plasma jet will be presented, the lengths of the jets and the spatial distributions of the species excited by the plasmas in open air will be investigated.