A Cold Electron Source Suitable for Mass Spectrometry

Abstract

An electron emitting source, which operates at ambient temperature, has been developed for instrumental applications including its use for electron emission in an ion source of a mass spectrometer. By the proper generation of a high resistance micron size gap in an electrically conducting tin oxide film, electrons will be emitted at the region of the gap. When the tin oxide film gap is located at the edge of the inner diameter of a very short length of capillary tubing, electron emission of 100 to 200 μA can be typically achieved with 300 V potential placed across the gap. Power consumption for the operation of this device usually remains below 300 mW. If the capillary tubing is made longer and the electrons are made to traverse the length of the capillary bore, a collimated electron beam will emerge at currents appreciably less than above with a diameter equal to the bore of the capillary. If the gap in the tin oxide film is located down in the bore of the capillary, the application of the operating potential will cause the electrons to emerge at one end while an ion current proportional to the pressure in the system comes out the other end.