Mass spectrometer

Abstract

In a mass spectrometer, an ion of a sample gas is produced in an ion source by colliding the gas with an electron beam, and is introduced into a magnetic field or an electric field. The ion is separated based on the mass number, and the sample is analyzed from a mass spectrum. The ion source has an electrode made of stainless steel, which is baked at a temperature in a range from 200° C. to 700° C. in an air atmosphere.

What is claimed is:  
     
         1 . A mass spectrometer for analyzing a sample gas, comprising: 
 means for producing an ion of the sample gas through collision of the gas with an electron beam, said producing means having an electrode made of stainless steel baked at a temperature in a range of 200° C. to 700° C. in an air atmosphere, and    means for processing the sample ion, said processing means guiding the sample ion into one of a magnetic field and an electric field for separating the ion according to a mass number to obtain a mass spectrum for analysis.    
     
     
         2 . A mass spectrometer according to  claim 1 , wherein said producing means is an ion source or an ion trap.  
     
     
         3 . A mass spectrometer according to  claim 1 , wherein said electrode made of stainless steel includes a chromium dioxide and chromium oxide on an outer surface thereof.  
     
     
         4 . A mass spectrometer according to  claim 3 , wherein said producing means includes an ionization chamber having a sample inlet and an ion exit, a filament formed at one side of the ionization chamber for producing thermo electrons, and a trap electrode formed at a side opposite to the filament for receiving the thermo electrons so that the sample gas introduced into the ionization chamber through the sample inlet is collided with the thermo electrons to produce ions of the sample, said ions being ejected through the ion exit.