Design of Broad Energy Range Focusing Reflectron for Time of Flight Mass Spectrometer

Ion energy distribution is one of the main factors that influence the resolution of time-of-flight mass spectrometer (TOF MS). One-stage or dual-stage energy focusing method was used to improve the resolution of TOF MS by reducing the ion flight time range. This method was very efficient for the ions with low energy range and large energy range ions, the resolution reduced rapidly. Thus, a broad energy range focusing reflectron method was proposed by Vlasak P. R. for TOF MS, which was applied the various voltages for the electrodes with certain distances. In this paper, a modified method was put forward by optimizing the distance and voltage of the electrodes for the reflectron simultaneously, and the validity of the method was proved by SIMION simulation. The errors caused by machining precision and assembly accuracy could be compensated by adjusting the voltages of the electrodes. To prevent the penetration of the fields, the electrodes should be equipped with grids. But the transmission of the ions will decrease very fast with the number of the grids increasing. By this method, the intensity of the first stage electric field was much larger than the others. Apart from the first two stage electric field, the intensity of the electric field was only a little larger than the field before. So all the grids can be removed but only the first two grids, which can prevent the first stage electric field penetrate to other fields. The penetration of other fields can be compensated by adjusting the electrodes voltages a bit. The simulation results showed that the method is simple and effective, and has strong practicability.