Apparatus and method for inhibiting ionization source filament failure

摘要

An ion source apparatus for a mass spectrometer comprises a refractory metal filament operable to provide a flow of electrons by thermionic emission; an electrical current source electrically coupled to the filament for heating the filament; a vacuum chamber enclosing the filament; an ionization volume within the vacuum chamber capable of receiving the flow of electrons; a source of an oxygen-providing gas or gases; a restrictive fluidic coupling to the source of oxygen-providing gas or gases; and a gas conduit fluidically coupled to the restrictive fluidic coupling, the restrictive fluidic coupling and conduit operable to provide a flow of the oxygen-providing gas or gases into the vacuum chamber so as to maintain a partial pressure of said gas or gases within the vacuum chamber that is sufficiently high so as to inhibit the otherwise formation of a carbonaceous growth on the filament in the presence of a gaseous carbon-containing material.

主权项

1. A method of operating an ion source for a mass spectrometer comprising:
providing a refractory metal thermionic filament positioned within a vacuum chamber, wherein the filament is fabricated from rhenium or a rhenium alloy; passing a current through the filament to generate a stream of electrons wherein the filament is operated at a temperature in excess of 1200 degrees Kelvin; introducing a carbonaceous gas including one of a reagent gas or a sample gas into the vacuum chamber, wherein molecules in the gas interact with the stream of electrons or with ionized background gases to form ions, wherein a portion of the gas comes into contact with surfaces of the filament such that carbon from the carbonaceous gas is dissolved in the filament, resulting in the subsequent formation of at least one carbonaceous growth on the filament; and, introducing an oxygen-containing gas devoid of fluorine gas or nitrogen trifluoride into the vacuum chamber, wherein the oxygen-containing gas removes all or part of the carbonaceous growth or inhibits its formation.