The Power System Of The Reflection-Type Time-of-flight Mass Spectrometer Introduced Vertically Is Designed And Implemented

Time of flight mass spectrometer(TOFMS)is widely used in ion detection due to their rapid detection speed in microseconds,high sensitivity and accuracy,and ease of use with multiple ion sources.Through analysis and research on the mass analyzer of the time-of-flight mass spectrometer,it is found that the high-voltage pulsed power supply is an important factor affecting the performance of the mass spectrometer.However,the pulse waveform output by the commonly used high-voltage pulse power supply has the problems of poor stability,difficulty in real-time adjustment of amplitude and frequency,or too narrow adjustment range,and long rising edge time.Using such a power supply system will degrade the performance of the TOFMS.In order to solve this problem,a set of high voltage pulse power supply system for vertically introduced reflection time-of-flight mass spectrometer is developed.The system can simultaneously output two high voltage pulse signals with low ripple,low rising edge and continuously adjustable amplitude and frequency,and one RF signal with continuously adjustable amplitude and frequency.The main work is as follows:Firstly,according to the kinematics theory,the motion process of ions in the reflection timeof-flight mass analyzer is modeled,and the effective time-of-flight of ions is expanded by Taylor expansion to obtain the second-order focusing conditions of ions,The implementation scheme and performance index of the high-quality power supply system are preliminarily determined,which lays a theoretical foundation for the subsequent circuit design.Secondly,the simulation software is used to simulate the movement of ions in the mass spectrometer.By comparing the flight results of ions in the second-order focusing and non secondorder focusing conditions,it is proved that the smaller the ion beam dispersion is,the more concentrated the time for ions of the same mass to reach the detection plate is.Then change the ripple size and rising edge time of the high voltage pulse power supply to verify that the pulse signal with high stability and short rising edge can improve the performance of the instrument.Then,the power system is designed,and the key components of the system are selected.The power supply circuit selects safe and reliable power module with small ripple,and the control circuit selects FPGA as the signal source.Two groups of counters in FPGA chip are used to control the duration of IO low level and high level respectively to control the pulse width and frequency of square wave.In the high voltage pulse generation circuit,the differential circuit composed of magnetic ring is matched with the load by simulation software,and the RF simulation circuit is built.The simulation results verify the feasibility of the scheme.Finally,the power system is drawn and implemented,and the upper computer control software is written for subsequent test and analysis.In order to make the magnetic ring transformer in the RF circuit work near the resonant frequency,several groups of magnetic ring transformers are tested,and the winding ratio is 17:23,Φ47*27*15mm magnetic ring transformer.The experimental results show that the output frequency and amplitude of the high voltage pulse have a certain influence on the rise time,and the pulse width has little influence on the rise time,and the rise edge is less than 100 ns,which achieves the expected effect.The pulse power supply system studied in this paper can meet the requirements of high precision and high resolution for vertically introduced reflection time-of-flight mass spectrometer.