Study On The Mechanism Of Ionization By Dielectric Barrier Discharge Ion Source

Ambient mass spectrometry ion sources is another revolutionary mass spectrometer ion source after the electrospray ion source and the matrix-assisted laser desorption ion source.The ion source can ionize the sample under the open normal temperature and pressure environment and no need for complex sample preparation processes,so it has driven the development of mass spectrometry to real-time,surface,and in situ ionization.Among tHem,the dielectric barrier discharge ion source(DBDI)has become a research hotspot in the Ambient mass spectrometry ion sources due to its simple structure,easy miniaturization and strong stability.DBDI excites an inert gas such as helium to form a plasma under the condition of dielectric barrier to ionize the sample.However,the particle composition in the plasma is complex,and the influence of different particles in the plasma on the ionization of the sample is remain unknown.Therefore,studying the ionization mechanism of DBDI to understand its ionization process have great significance for improving the ionization efficiency and soft ionization effect of ion source and application research of future.In view of the above problems,this paper studies the mechanism of DBDI ionization from the following four parts.A miniature quartz capillary DBDI with surface two-electrode structure is realized,which can produce good and stable plasma jet.Then design and construct the DBDI discharge experimental platform,which provides an experimental basis for the later DBDI mechanism research.Analysis the plasma spectra generated by DBDI.The spatial distribution of each ion in the quartz capillary was studied in detail.The DBDI ionization process using helium as the discharge gas was judged and elaborated.Analyze the influence on the plasma and plasma current by different discharge modes then analyze the effects on each ions by discharge mode.Finally,investigate the effects on the critical voltage by the discharge voltage,the gas flow rate and the electrode spacing.Investigate the effects on each ion in different discharge modes of DBDI and then investigate the effects on plasma in different discharge modes when the power supply was at the cutoff frequency.