1. Electronic impact source

Nier source mass spectrometers, also known as electron impact mass spectrometers, are used to measure the concentrations and isotopic compositions of elements (H ₂ , CO ₂ , N ₂ , noble gases, etc.). They consist of three distinct elements namely, a source to ionize the gases, a magnetic sector to separate the isotopes according to their m/q ratio and several collectors to transform ionic fluxes into measurable electrical currents (figure 1 ).