The interaction between the supersonic molecular beam and electron beam for the optimization of an electron ionization ion source

The interaction between the supersonic molecular beam (SMB) and electron beam is a key issue in the design of electron ionization mass spectrometry with SMB (EI-MS with SMB). In this paper, one EI ion source prototype was designed based on an electron gun, whose filament was far away from the interaction range and the influence of the filament field could be neglected. The interaction was studied by one high-speed camera and one Faraday cup. The ion flux as well as the variation with stagnation pressure and axial distance was studied. The experimental results were consistent with the simple simulated results about the ionization and photon emission process in the interaction. It was found that higher stagnation pressure was necessary for higher electron energy to acquire the maximum ion flux. The optimized parameters for the EI ion source including the axial position, stagnation pressure, and electron energy were reported. These results were meaningful for the design and optimization of the ion source. Published under license by AIP Publishing.