Realization of Atmospheric Pressure Glow Discharge Ion Source in Small Gap with Precise Electrode Structure

The influence of electrode precision on the atmospheric pressure glow discharge was analysed. A line-cylinder ion source with precise electrodes was designed and fabricated. The diameters of the inner and outer electrodes were 0. 16 mm and 4 mm respectively. When the applied voltage reached3. 5 kV, the corona discharge started and the waveform of the discharge current was the typical Trichel pulse. When the applied voltage rose to4. 5 kV,the discharge current became direct current,showing that the discharge was completely operated in glow discharge mode. The transition from corona discharge to glow discharge can be clearly observed by the discharge current waveform. And the physical process was analysed. The discharge experiment shows that the system can generate stable atmospheric pressure glow discharge. The discharge current is in direct proportion to the applied voltage and the voltage between the electrodes keeps constant when the discharge current increases. All these discharge characters are in line with the low pressure glow discharge. The discharge current can reach the order of milliampere. Therefore,the ionization degree is higher enough to improve the detection sensitivity effectively. The mass spectrometer experiments show that the ion source can well ionize the chemicals such as formic acid,acetic acid,phenol,and benzoic acid and so on.