Development of Micro-sized Rectangular Ion Trap Based on Micro-Electro-Mechanical System Processing Technology

Rectangular ion trap (RIT) has the advantages of high capture efficiency and large storage capacity of linear ion trap (LIT), as well as the advantages of cylindrical ion trap (CIT) which is easy to process and assemble, so it is conducive to miniaturization. The miniaturization of ion trap has certain requirements on the accuracy of machining technology and the flatness of machining surface, but the conventional machining method can not produce enough accurate electric field on the scale of micrometer. In order to further study the microminiaturization of RIT, micro electromechanical system (MEMS) and laser cutting technology were used to fabricate the micro rectangular ion trap, and the relationship between the parameters of RIT and its internal electric field components was analyzed by simulation. The simulation results showed that the high-order fields inside the micro RIT are mainly octopolar field and duodecuple field. At the scanning speed of 2 530 Th/s, when the field radius in the non-emission direction of the ion trap was 1.4 mm, the field radius in the ion emission direction was 1.60 mm, and the electrode thickness was 50 μm, the mass resolution of the ion with m/z 119 could reach 452. The results of simulation analysis were combined with process characteristics to determine the structural parameters of micro RIT. Non silicon MEMS technology was used to prepare high-precision, micron level exit direction electrode, which had a great impact on the performance of ion trap. The overall alignment and assembly of the ion trap was achieved by laser cutting and precision tenon-and-mortise structure, and mass spectrometric analysis tests were performed to verify its performance. Experiment showed that micro RIT can analyze the mass of toluene and other ions with mass less than 100 and the mass resolution is higher than 200, which proves the correctness of structure design and the feasibility of MEMS process, and lays a good foundation for the development of the microminiaturization of the RIT.