Simulated and developed an electron impact ionization source for space miniature time-of-flight mass spectrometer

Based on the ions initial distribution and electrodes parameters of electron impact (EI) ionization source, the physical model of miniature EI source is developed by SIMION 8.1. By using the phase space analysis method, we have researched the influence of the initial position of ions voltage parameters of electrodes on focusing performance, ion transmission efficiency and velocity distribution of ions when they exited from the focusing electrode. It is found that when negative voltage is applied to the object slit S of the EI source, the position and velocity distributions of the ions at the exit are minimized, the performance of the EI source is greatly improved due to the secondary focusing of the ions in this case. Based on the above research, we developed the integrated EI source, the EI source's overall size is 12 mm wide, 24 mm long and 12 mm tall, it weighs 0.1 kg, and its power consumption was measured to be 1 W. Finally, the primary performance of the EI source coupled to reflection time-of-flight mass spectrometer (RTOF MS) is evaluated and the experiment results are consistent with simulation results.