Patent ID: 9159542
Filing Date: 2015-10-13
Classification: H01J

Abstract:
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.