Development Of DC/PULSE Dual Output Glow Source

Glow source is a device for direct ionization of solid samples,which is widely used in the field of multi-element analysis of solid materials.With the urgent need for detection in the field of new materials,higher voltage discharge,multi-mode output and multi-type sample detection have become the development direction of glow source.This paper mainly studies the implementation forms of DC glow source and pulse glow source,designs a highly integrated two-stage booster DC/pulse dual output glow source,and builds a set of glow source experiment platform.By analyzing the operating characteristics of flyback converter,push-pull converter,half-bridge converter and full-bridge converter,the push-pull structure is designed as the first-stage booster unit.In order to meet the requirements of high integration design,the lossless buffering absorption scheme and DC and pulse dual output scheme are proposed.In addition,according to the application requirements,this paper designed the mechanical structure of cathode and anode,focusing ion lens,vacuum cavity and feed-through interface suitable for the analysis of flake samples and rod samples,and then verified the feasibility of the scheme through COMSOL simulation.Based on the analysis of the working principle of push-pull boost converter and voltage doubling rectifier,the parameters of high frequency transformer,power switch tube,lossless buffer absorption circuit,capacitor and diode of double voltage rectifier circuit are designed in detail.The function modules of PWM pulse width modulation,voltage and current sampling and auxiliary power supply with DSP as the core controller are developed.Finally,the DC glow source is simulated and verified.It has been proved that the cascade of push-pull converter and double voltage rectifier circuit can achieve 2000 V DC output,and the output voltage ripple is less than 2Vpp.The lossless buffer-absorbing circuit can effectively suppress the switching tube voltage spike caused by transformer leakage.The DC glow source designed in this paper can meet the requirements of high dynamic regulation performance in complex glow discharge environment.Based on the research of DC glow source,Marx type pulse glow source is developed and its circuit principle is analyzed.Firstly,the parameters of full-bridge rectifier,LC filter,energy storage capacitor of pulse conversion circuit and power switch tube of push-pull converter are designed.In order to meet the special requirements of high voltage terminal floating output,this paper develops the function modules of low voltage signal and high voltage signal isolation transmission,voltage sampling and drive control of pulse glow source.The state equation transfer model and PID control model of pulse discharge circuit are established by small signal modeling method.The corresponding simulation of the model is carried out by MATLAB and PSpice,and the correctness and feasibility of the scheme are verified.The results show that the scheme can achieve stable discharge at discharge frequency of 2k Hz-5k Hz and pulse width of 10μs-50μs,and pulse rising edge is less than 200 ns,which accords with the design expectation.The designed pulsed glow source can effectively realize the function of fast pre-sputtering and slow DC discharge analysis in complex matrix environment.Finally,in order to cooperate with the double output glow source discharge,a set of glow source experiment platform was built in this paper,including a vacuum system,glow discharge vacuum chamber,glow discharge cathode and anode suitable for flake and rod samples,high voltage and fluid feed-through structure,and ion focusing transmission system.Thus,the glow source is formed with the DC/pulse double output glow source circuit system,which lays the foundation for the combination with high resolution magnetoelectric dual focusing mass spectrometer.