Patent ID: 6700119
Filing Date: 2004-03-02
Classification: H01J

Abstract:
An ion source for a mass spectrum which operates at a low pressure comprising:an atmospheric pressure sample ioniser operable at atmospheric pressure to provide a sample flow containing desired sample ions; an interface chamber having an entrance aperture, and exit aperture and exhaust port, the entrance aperture being arranged to receive sample ioniser entrained in a gas flow, and the exit aperture being arranged for sample ions to exit the interface chamber to the mass spectrometer, and a vacuum pump in communication with the exhaust port of the interface chamber to hold the pressure thereof at a pressure intermediate the operating pressure of the mass spectrometer and atmospheric pressure; the interface chamber defining a flow passage for gas and entrained sample ions from the entrance aperture to the exhaust port, the exit aperture being located in the flow passage between the entrance aperture and the exhaust port, wherein the flow passage is shaped to redirect substantially all the gas and entrained sample ions entering the entrance aperture before they reach the exit aperture and to cause said redirected ions to flow within a distance â€œdâ€  of the exit aperture, where d is less than five times the diameter of the exit aperture, and to provide no line of sight between the entrance and exit apertures.