Patent ID: 6462336
Filing Date: 2002-10-08
Classification: H01J

Abstract:
An ion source for a mass spectrometer, the mass spectrometer being operable at a first, low pressure, the ion source comprising:an atmospheric pressure sample ionizer operative at a second, atmospheric pressure, the ionizer being arranged to provide a sample flow containing desired sample ions entrained with undesired gas and droplets; an interface chamber having an evacuation port; and a vacuum pump connected to the evacuation port so as to hold the said interface chamber at a third, intermediate pressure which is higher than the said first, low pressure at which the mass spectrometer operates, but lower than the said second, atmospheric pressure; the interface chamber her comprising: an entrance orifice located so as to receive the said sample flow into the said interface chamber, wherein the said entrance orifice has a flow axis and wherein the entrance orifice causes the sample flow to form a stream of gas along the said flow axis and into said interface chamber; and an exit orifice for sample ions to exit the said interface chamber to the said mass spectrometer; wherein the interface chamber is arranged to disrupt said stream of gas to provide a dead region within said chamber, the dead region having no net gas flow direction and wherein said exit orifice is located in said dead region.