A Study On Miniature Ion Trap Mass Analyzer

Mass Spectrometer(MS) is a common instrument used for detecting and analyzing compounds qualitatively and quantitatively. It has a wide range of applications, including research, industry, life, national defense and so on. The working principle of MS is that ions moving in the electromagnetic field is selected according to their mass-charge ratio and detected. After a century of evolution, various types of MSs have been developed, while the performance of the MS is also rising. At present, MS has two main developing trends: the first is the development of MS with high-performance including macromolecules detection, high-throughput, high sensitivity, high resolution and accuracy, which is primarily used for the laboratory analysis of high levels; the second is the development of miniature portable mass spectrometers, mainly for rapid field detection and analysis, and some special occasions on which the equipment size and weight are strictly restrained. In fact, any type of MS can be miniature. However, the ion trap mass spectrometer(ITMS) has many advantages in miniaturization, as follow.1. Owning high sensitivity;2. The working radio frequency voltage is low.3. In ITMS the ion trajectory is shorter. At higher air pressure the average free path is long enough to meet the need of normal analysis;4. ITMS can be used as MS/MS, then it can use the ion / molecule reactions to identify the specific compounds with high selectivity in complex mixtures.Because of the trend of miniature and advantages of ITMS in miniaturization, the miniature ion mass analyzers were researched in this article. The working principle of ion tarp mass spectrometer is that ions different mass-charge ratio have different stability in the quadrupole field produced in ion trap mass analyzer, The stability of ions will change with the operational conditions, then the ions with different mass-charge ratio can be separated to be detected. Considering of different performance levels of demand and ease of fabrication, many ion tarp mass analyzers were proposed, from the traditional 3D ion trap to the cylindrical ion trap(CIT), to the rectilinear ion trap(RIT) and the recent PCB ion trap.Three aspects were mentioned in this article:1. The study and fabrication of RIT. RIT which is a simplified one was brought out based on the traditional 3D ion trap mass analyzer. The influence factors of performance of RIT had been studied by using SIMION ion optical simulation program in the paper. It was studied that x0-y0 ratio, the identity of the cross section, the dislocation and misalignment of electrodes affected the trapping efficiency and ejection efficiency. In addition, the RIT was designed optimally by analyzing the internal electric field in the RIT. Finally, the RIT was fabricated in the way of traditional machining method based on the simulation results.2. The study and fabrication of planar linear ion trap mass analyzer(PLIT) based on micro electro mechanical systems (MEMS). PLIT is a more simple ion trap mass analyzer with a advantage of low-cost which was suitable for miniature ITMS. The MEMS technology can make up for the deficiencies of PCB technology about the precision and yield. In this article, the effects of geometry on the performances of PLIT was studied firstly. Then the geometry of PLIT based on MEMS was designed with the results of simulations. At last, the process of MEMS technology was proposed and the PLIT based on MEMS was fabricated. At the same time, other factors which affected the performance of PLIT based on MEMS were discussed, and the corresponding solutions were brought up.3. The simulation and technological process of the diamond-shaped ion trap(DIT) based on MEMS. DIT proposed in this article is a new type of ion trap mass analyzer, which is based on the advantage of wet etching of MEMS technology that the etching velocity of different crystal surfaces are different on different. Firstly, the geometry structure of DIT was described, and the advantages of DIT were given including high precision, good reproducibility and an array of convenient. Then, the basic performances of DIT which include trapping efficiency and ejection efficiency were simulated by using SIMION ion optical program. Meanwhile, the optimal geometry of DIT was designed with the results of simulations. Finally, the technological process of DIT based on MEMS was brought up. At the same time, the other factors which affect the performance of DIT based on MEMS were discussed , and the corresponding solutions were proposed.In this article, the study of miniature ion trap mass analyzer was mainly carried out by the simulation of SIMION program, then the optimal geometry structure was obtained. Finally, the ion trap mass analyzers were fabricated in the way of traditional mechanical method or MEMS technology. At last, the three ion trap mass analyzers were compared and prospectedIn this paper, miniaturized ion trap mass analyzer of the study, mainly through simulation software SIMION ion trap mass analyzer of the performance simulation, and optimization of the structure as drawn. Then, through traditional machining or MEMS processing methods to produce the corresponding ion trap mass analyzer. Finally, the three ion trap mass analyzer were compared, and the further research of miniature ion trap mass analyzer was proposed.