Abstract: GS-250 Type Mass Spectrometer for Trace Gas AnalysisMao Fuming(Dept.of Electronic Engineering,Southeast University,Nanjing 210018,China)Received Abstract:A trace gas analysis mass spectrometer is reported.It is composed of a qudrupole MS with a special ion source and sampling system.The ionization chamber of the ion source can be operated to linear pressure 6 Pa or unlinear pressure 100 Pa.The interference of the ground pressure in vacuum system and hot temperature filament can be negligible.Eventhrough MS work at 10-4Pa high vacuum system,the trace gas sensitivity still reaches to 1×10-6.This instrument can be used in industrial gas manufacture andintegrated circuit factories.Keywords:qudrupole mass spectrometer,trace gas analysis,enclosed ion source.