| 摘要 |
PURPOSE: To enable measurement of very small amounts of impurities in high- purity gas by reducing the rate of generation of impurities from the ion source of an atmospheric ionization mass spectrometer. CONSTITUTION: Of the surfaces of components constituting an ion source, those which, when incorporated into an ionization chamber 3, face the interior of the ionization chamber have their difference in height reduced, and are formed from a material that adsorbs little gas and impurities included in the gas. The surfaces of the components are flattened in such a manner that the surfaces of a current introducing terminal 4 and the like which grip a needlelike electrode 20 are coplanar, and that the surface roughness of the metallic member of a contact gas part is reduced to a maximum of 0.5μm or less in terms of surface irregularities. Further, a high-density ceramic with a density of 2.7g/cm<2> or less and 0% water absorption is used in an insulating member 6 to reduce as much of the amount of adhering water as possible, while a material whose degassing property is as low as 1.0×10<-3> (Pa.l/sec) or less (at 120 deg.C) is used in a sealant 15 of the connection between a gas inlet and a gas outlet.
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