| Ion mobility spectrometry(IMS)is widely used in the detection of dangerous substances.The ion source ionizes is one of the key technologies of IMS.The commonly used ion source is radioactive source.However,due to its radioactivity,a new ion source is required to replace traditional radioactive ion sources.In this paper,a needle-cylinder type plasma generator based on dielectric barrier discharge(DBD),as well as a power supply for driving the discharges,is developed.The characteristics of the plasma generator are studied experimentally,and the circuit simulation of the designed power supply is also conducted.The major conclusions are as follows:1)The needle-cylinder type generator is designed.The type and thickness of the dielectric layers covering the powered electrode are also compared and analyzed.Then,the control variable method is used to study the characteristics of the plasma generators.The current-voltage characteristics,discharge images and emission spectra under different operating conditions are obtained.The initial discharge voltage of the generator,the glow-to-arc mode transition voltage and the optimum driving frequency of the power supply are obtained.2)With the combination of the plasma generator and the IMS,the ion mobility spectra are obtained under different discharge conditions.Then,the control variable method is used to conduct experiment with discharge voltage and ion gas flowrate as variables.While IMS equipment is working in optimal state,the optimum ion gas flowrate and the current discharge voltage of generator are obtained.3)The power supplies for driving the discharges are designed based on the hysteresis comparator and UC3842 chip,respectively.Based on this,the AC power supply circuit based on STM32 is designed.In addition,the power protection function is designed with a manual input of the threshold value,as well as the monitor of the power supply parameters,in the principal computer windows.Figure 49;Table 10;Reference 60. |
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